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SemiAnalysis · · 44 分钟

第038期:GLM 5.3 是来自中国的 Mythos 级网络安全模型吗?(InferenceX)

Kimbo ChenWenyao GaoJordan Nanos

AI与软件半导体技术
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TL;DR
  • GLM-5.3 的效率提升,并不直接构成内存需求走弱的看空信号。 Kimbo强调,稀疏注意力缓解带宽压力,却无法消除 KV cache 的容量需求:“相关上下文里的所有 token 仍然都得保留。”HiSparse在 HBM 和 DRAM 之间迁移缓存,以支持更高并发;Jordan预计,推理服务成本下降,长期将带来“更多 HBM 和更多带宽”。
  • GLM-5.3 发布数周后,AMD MI355 已在推理成本上向 NVIDIA 发起挑战。 Wenyao称,单用户速度达到每秒150 token时,成本大致追平 B200;Jordan还提到,MI355 单用户速度达到每秒100 token时的吞吐表现。InferenceX数据显示,“红色 AMD 曲线反超绿色 Nvidia 曲线”,随后 NVIDIA 又提升了表现——推理引擎优化由此成为不断变化的竞争变量。
  • 极低延迟与总吞吐最大化,背后的经济账并不相同。 TailRT通过解码 megakernel,在 batch size 为1时速度最高可达每秒470 token,但无法服务大 batch。Kimbo认为,在这一场景下,内存带宽“最重要”;Wenyao则说自己不用超高速模式:“太贵了。”
  • GLM-5.3 能力跃升,据称来自后训练,而不是更大的基础模型。 Wenyao称,智能体基准提升超过10%;Kimbo认为,GLM-5.2 到 GLM-5.3 在网络安全能力上的变化“判若云泥”。Jordan称 GLM-5.3 是“前沿网络安全模型”,依据是他在 CVP 威胁攻防演练工作中遇到 Anthropic 和 OpenAI 拒答,随后转而使用 GLM-5.3。Kimbo认为它“肯定不是 Mythos 级”,但暂时将其归为接近 Fable 的水平。
  • Z.ai 的优势或许不只在新算法,也在研究推进速度。 Jordan提出,常见后训练方法并非独家优势;在相同算力下,以更低成本跑更多实验,也能形成优势。Kimbo提到基于 critic 的 SAO 训练和 SLIME,称后者“可以说是设计最好的”框架之一;不过,他也提醒,GLM-5 之后尚未发布详细技术报告。
  • 中国芯片部署是公开说法;针对特定供应商做优化仍只是推测。 GLM-5 论文称模型首日即可适配7个国产平台;Z.ai则称 OxAlpha/GLM-5.3 Flash 完全运行在中国硬件上——Kimbo对此的前提是“假设大家都诚实”。他估算的约120算术强度大致与 Moore Threads 芯片相符,但明确表示,这既不能证明模型针对这些芯片做了优化,也不能证明实际部署情况。
  • 下一轮提升或来自混合注意力扩展,或来自针对专门工作流的后训练。 Kimbo称 GLM-5.3 Flash“简直像个弗兰肯斯坦模型”,将 DSA 与 Kimi Delta Attention 结合;他猜测,把这种混合架构扩展到 GLM-5.3 的规模,可能带来进一步提升。Wenyao设想的企业路径,则是在专有数据上做后训练,而不是出资从头预训练。
摘要 · 为研究而整理的核心内容

1. 稀疏注意力缓解带宽压力,但不解决缓存容量

  • Kimbo Chen的区分是:线性注意力改变注意力算法,稀疏注意力则保留原有算法,同时筛选最相关的 token。从 GLM-5 起,Z.ai 使用 DeepSeek Sparse Attention;这项技术随 DeepSeek-V3.2 推出,由 Lightning Indexer 为基于 Multi-Head Latent Attention 的注意力机制筛选 token。Kimbo认为,百万 token 级会话无法采用 dense attention;Jordan则强调,效率是以合理成本服务这类会话的关键。
  • Kimbo不认同稀疏注意力解决了 KV cache 容量问题:相关上下文中的“所有 token 仍然都得保留”。HiSparse 是 HiCache 的稀疏注意力版本,它将缓存从 HBM 卸载到容量更大、带宽更低的 DRAM,再把相关部分调回。带宽节省与容量扩展,是两种不同机制。
  • Wenyao Gao以 B200 为例,展示了并发度为8和16时,主机内存占比存在显著差异。B200每颗芯片的内存少于 B300,因此这一影响在 B200 上更明显。回想 DeepSeek V3 和 R1 发布前后的内存股抛售,Jordan认为,效率提升会让更多用户用上服务,并不必然减少内存需求。他对杰文斯悖论的判断是:“会需要更多 HBM 和更多带宽。”

2. 服务软件改变成本曲线,AMD 正在追赶

  • Wenyao称,NVIDIA 在发布初期领先;数周内,AMD 已能在单用户速度达到每秒150 token时,把成本降到大致与 B200 持平。Jordan纠正了时间线:GLM-5.3 是8月初推出,不是10月;他还提到 MI355 单用户速度达到每秒100 token时的吞吐表现。InferenceX 的历史曲线显示,“红色 AMD 曲线反超绿色 Nvidia 曲线”,随后 NVIDIA 又提升了表现。
  • Jordan指出,峰值效率约为每1美元总拥有成本(TCO)对应4500万 token。Wenyao解释,芯片的固定能力是一回事,推理引擎的开发又是另一回事:AMD 工程师“连夜奋战”,反复优化软件,追上许多 NVIDIA 芯片的每百万 token 成本。
  • Wenyao以低延迟场景举例,谈到 TailRT:解码 megakernel 降低了启动开销,在 batch size 为1时速度最高可达每秒470 token,但无法服务大 batch。将数据卸载到 DRAM 会增加延迟,尤其影响尾延迟。他用 Jane Street 希望在几秒内拿到答案的需求,对比自己的日常智能体任务:“我可以等,只要成本可承受,就尽量把输出做大。”
  • Jordan将这一取舍与外界讨论的 Rubin Ultra 配置联系起来:每 GPU 的容量从1 TB降至192,同时保留带宽。Kimbo认为,这体现了对带宽的优先考虑:在极低延迟场景里,“你拼的是加载模型的速度”。容量仍然重要,但缓存、网络,以及让数据传输与计算重叠,都能缓解容量短缺。

3. 后训练带来能力跃升,技术披露仍有限

  • Jordan称 GLM-5.3 是“前沿网络安全模型”,依据是他在 CVP 威胁攻防演练工作中遇到 Anthropic 和 OpenAI 模型拒答;他表示自己转而使用 GLM-5.3,并指出其权重可以下载。Kimbo反对最强的那种比较:“从技术上说,它肯定不是 Mythos 级。”他暂时认为其接近 Fable 水平,但不确定 Anthropic 对这一等级的确切称呼。
  • Wenyao称这次发布是一次“警钟”:智能体基准提升超过10%,靠的是后训练,而不是重新进行预训练。Kimbo形容 GLM-5.2 和 GLM-5.3 在网络安全能力上的差异“判若云泥”。在他们看来,这说明不扩大模型规模,也能通过后训练大幅提升能力。
  • Kimbo介绍,第一阶段采用同步 GRPO,优先保证稳定性。智能体任务序列更长,奖励信号可能被稀释,因此第二阶段改用更接近 REINFORCE 的变体,容忍策略滞后。这样一来,团队可以使用较旧或最新的策略,无须大量计算重要性比率和策略滞后。
  • Kimbo还提到一种 PPO 风格的训练方法:由 critic 为 rollout 打分,并与 actor 同步训练,即 Single-Rollout Asynchronous Optimization(SAO)。但有一点需要注意:GLM-5 之后,团队没有发布详细技术报告;Kimbo的说法综合了研究人员交流、公开公告和已发表研究。
  • Jordan质疑,常见算法是否足以构成独特优势;Kimbo起初也认同这些方法并非 Z.ai 独有。Jordan随后指出,在相同算力下,效率本身就能让团队跑更多实验、开展更多研究任务。Kimbo称 SAO 是一项明确创新,并认为 SLIME“可以说是设计最好的后训练框架之一,甚至可能就是最好”。

4. 中国芯片部署有公开说法;供应商定向协同设计尚未证实

  • Jordan援引 GLM-5 论文的说法:模型“从第一天起”就实现了“面向中国 GPU 生态的全栈适配”,覆盖从内核到推理框架的7个平台,分别是 Huawei Ascend、Moore Threads、Hygon、Cambricon、Kunlunxin、MetaX 和 Enflame。他的重点是,基础设施优化不一定要围绕 NVIDIA 或 AMD 展开。
  • Kimbo补充,Z.ai公开称,以 OxAlpha 为名的 GLM-5.3 Flash 完全运行在中国硬件上。他回忆,有测试认为 OxAlpha 已经服务了“差不多100万亿 token”,这一数字让人怀疑中国实验室能否用 GPU 承载如此规模。Jordan称 OxAlpha 于8月20日出现在 OpenRouter 上。Kimbo明确加上前提:“假设大家都诚实”;但他认为,Z.ai 已经解决了足够多的内核和系统障碍,能够高效提供服务。
  • Kimbo估算,GLM-5.x 解码阶段的算术强度约为120。DeepSeek 曾针对 H800 做模型适配;他估算 GLM 的配置似乎更适合 Moore Threads GPU。他认为,GLM 的配置对 B200 或 H200 并非最优:模型可能面向其他硬件,也可能出于未披露的原因,牺牲了软硬件协同优化。他称 Moore Threads 的说法是“阴谋论”:这一计算既不能证明模型针对这些芯片做了优化,也不能证明模型实际部署在这些芯片上。
  • Kimbo还提到,Z.ai称模型曾帮助陌生的非 GPU 硬件调通并验证 GPU 内核,同时监控任务运行,以提升系统效率。Wenyao认为,只要有合适的执行框架、工具和足够预算,智能体写出的内核可以比人类更快。被问到 AMD 的 TileRT megakernel 花了多少 token 时,Kimbo回答:“说实话,我不太清楚。”

5. 下一轮提升或来自混合架构与专有数据

  • Kimbo猜测,Z.ai 很可能会在后续 GLM-5.x 版本中沿用现有架构,例如 GLM-5.4;另一条路径则是 GLM-5.3 Flash。后者“简直像个弗兰肯斯坦模型”,将 DSA 与 Kimi Delta Attention 混在一起。他猜测,Z.ai 可以把这种混合架构扩展到 GLM-5.3 的规模,并进一步提升性能或能力。
  • Kimbo称,GLM-5.3 于8月初推出,GLM-5.3 Flash 则在8月下旬发布;他估计 Flash 可能只训练了2到3个月,其中2个月是较激进的估算。他还指出,在 Kimi K3 于7月中旬推出之前,押注 KDA 就是一笔重注。
  • Wenyao认为,在专有数据上做后训练,可以改善特定工作流,不必出资从头预训练;他举例提到 Harvey 基于 Kimi 的智能体,以及 Periodic Labs 的 AI for Science 工作。他还设想,市场上会同时存在2万亿或3万亿参数的大模型,以及高效、“够用”的模型,企业用后者时无需担心成本。
  • 仍未解开的变量是人力投入。Kimbo称,Z.ai曾在 GLM-5.2 和 GLM-5.3 的讨论中提到“大量人力”,但没有说明具体做什么。他“相当确定”这指的是标注;至于标注类型和投入细节,仍然没有答案。
完整逐字稿
Jordan Nanos

This week, I’m joined by Wenyao and Kimbo. We’re going to talk about everything GLM-5.3. They put out a great article recently. The model is about 2 months old, and we’ve got everything from InferenceX performance results to model architecture, post-training pipeline, and what people are using it for. Spoiler alert: there are lots of discussions around this model’s cybersecurity capabilities. Kimbo, Wenyao, welcome to the show.

Kimbo Chen

Thanks for having me, Jordan.

Jordan Nanos

Awesome.

Wenyao Gao

Excited to be here.

Jordan Nanos

I can hear it in your voice, guys. The title of the article was “How GLM-5.3 Sparse Attention Affects HBM and Memory Usage.” For those who don’t know, maybe we can start with an introduction, Kimbo. What is sparse attention? Why do we care about HBM memory usage when we talk about these new open models, especially ones coming from Chinese companies like Z.ai?

Kimbo Chen

Sparse attention is a category of attention mechanism. In contrast to linear attention, which tries to change the core operation of attention—usually called scaled dot-product attention—sparse attention changes the way you select the number of tokens while keeping the core attention operation. Linear attention tries to change the fundamental algorithm into a linear-time algorithm, whereas sparse attention is about inventing some sort of token-selection algorithm.

The idea is that, regardless of how long the sequence or context becomes, you attend to only the most important, most relevant tokens at every forward pass.

Jordan Nanos

Awesome.

Jordan Nanos

This makes the model a lot more efficient, right? A lot of different labs are pursuing things like this to make attention more efficient. Can you give a comparison of what Z.ai is doing with the GLM models and what other labs like DeepSeek or Kimi are doing?

Kimbo Chen

Like you said, in some sense, it’s almost inevitable because of physics. We just don’t have enough memory or compute. Since GLM-5, GLM has used DeepSeek Sparse Attention, the attention mechanism DeepSeek invented for its DeepSeek-V3.2 model. GLM adopted that instead. The core components are a Lightning Indexer, which is the token-selection component, and the sparse attention itself. That sparse attention is based on the more standard Multi-Head Latent Attention invented by DeepSeek and popularized with DeepSeek-V3.

Even though DeepSeek invented DSA—DeepSeek Sparse Attention—with V3.2, they continued innovating and changing their attention variants. For the V4 series, they introduced CSA, or Compressed Sparse Attention, and Heavily Compressed Attention (HSA), which, roughly speaking, build on top of DSA and add more token-compression modules. For V4.1 Flash, they simplified HSA and CSA into a slightly different design.

Jordan Nanos

Sorry, I don’t mean to interrupt you. The reason they’re pursuing this is efficiency, right? People speculate that Chinese labs may care about this more than American labs because of the hardware restrictions they face. But roughly, the outcome of all these efforts in sparse attention is that the cost to serve tokens—in this chart, a million tokens—goes way down. It’s really cheap to serve if you can use sparse attention or additional techniques like HSA and stuff like that, right?

Kimbo Chen

Yeah, totally. It’s infeasible to fit that many tokens with dense attention anymore, given that our usage easily goes above a million tokens of context for a single session.

Jordan Nanos

Okay, Wenyao, let me bring you in here. When it comes to serving this model and analyzing the cost to serve a million tokens at 150 tokens per second, this involves running benchmarks that simulate a workload a real provider like Z.ai—or somebody else downloading and serving the model, like an inference endpoint provider—would actually incur. In other words, they want to serve dozens, hundreds, or even thousands of concurrent users on a single model endpoint. Can you talk about the restriction Kimbo just mentioned? If you’re going to support all these users with a million-token context, that’s going to put a lot of pressure on your system and the resources you have available, like memory, right?

Wenyao Gao

Absolutely. For serving, one of the factors people care about most is aggregated token output, because it represents how many total outputs you can produce for your users. There’s a trade-off here: we only have a fixed amount of memory on the GPU, and to get more concurrency and serve more users, we need more memory.

There’s a technique called HiCache, which serves as the prefix cache we use. When concurrency goes up, it offloads memory from HBM to DRAM, and that makes the percentage of host memory go up as concurrency increases. If you look at the B200 charts we have on HiCache, the percentage of host memory at concurrency levels of 8 and 16 is very different. This is even more pronounced on B200 than on B300, because B200 has less memory per chip. That’s a really interesting observation from our side.

Jordan Nanos

Kimbo, do you remember when HiSparse and HiCache were first introduced? These are clearly optimizations meant to save people money when they’re serving these models, which implies the people introducing them have a lot of users using their models that they need to worry about. It’s not a theoretical thing.

Kimbo Chen

HiSparse is the sparse-attention version of HiCache. The whole idea of HiCache is to offload the KV cache from HBM to a lower-tier, higher-capacity but lower-bandwidth memory, and only load the most relevant set of tokens during computation.

I think HiSparse is a good example of an explanation for a misconception: that sparse attention fixes all the problems of the KV cache consuming too much memory or having high memory requirements. Sparse attention doesn’t mitigate the memory-capacity bottleneck. It helps a lot with memory bandwidth. But for capacity, during sparse-attention computation you still need to select the tokens, so you still have to keep all the tokens in the relevant context. You cannot discard them during computation. At some point, they still have to be loaded into HBM, so memory-capacity consumption won’t be significantly reduced. That’s where HiSparse becomes useful, because it can apply typical caching rules so that you can load the most relevant parts into HBM.

Jordan Nanos

Okay, Wenyao—

Wenyao Gao

Yeah, definitely.

Jordan Nanos

Talk to me about some of the initial performance results here. The ability to use HiSparse versus HiCache on this model, GLM-5.3, is obviously giving some great performance results, especially for particular vendors, when you look at total tokens per $1 of TCO. Forty-five million tokens at peak up here—very, very efficient.

Wenyao Gao

It is. I just want to add to what Kimbo just said. One thing we want to emphasize in the article is that even though GLM is compute-efficient, that doesn’t mean it’s efficient on the memory side, because the model still needs to read through the relevant context history. HiSparse becomes very important. It offloads from HBM to DRAM, and offloading back is a very tricky technique that we’ve also introduced in the article.

As for the performance, I think Nvidia’s chips generally get ahead of all the other chips at the very beginning. A few weeks later, when we were about to ship the article, it was very surprising that AMD’s interactivity at 150 tokens per second was relatively the same cost as Nvidia’s B200 chips.

Jordan Nanos

Let me actually show that animation as we go through it right now. The models were released in early October—sorry, they were released in early August. We’re now in October. As you shift through and start to see these results show up on the dashboard, you can see the red AMD curves overtake the green Nvidia curves, which is quite impressive. Now Nvidia starts to come back up. Explain your experience here, because you guys are running this stuff every day. Lots of people have been anti-AMD for a long time, especially because of the AMD software ecosystem, including us.

Jordan Nanos

But this is a relevant model that’s not even 2 months old, and the best curves for the highest throughput—even at 100 tokens per second per user, which is a real interactivity range—are beyond what the inference endpoints I can see on OpenRouter are approaching. Those endpoints are below that. That’s a lot of high performance from AMD’s MI355. Good for them.

Wenyao Gao

Yeah, they’re definitely working hard overnight and trying a range of optimizations. I think it shows that there are 2 sides. The first side is the hardware, where hardware vendors like NVIDIA deliver their chips to customers, and the performance of those chips is fixed. On the other side is the inference engine, where you have to catch up, continue optimizing, and iterate over and over again to make sure your performance stays more cost-efficient. This is a perfect example: we see AMD engineers working hard on their engine, Adam, and over time its cost per million tokens has caught up to a lot of NVIDIA’s chips.

Jordan Nanos

Yeah. We have a live chart specifically looking at the prefix cache reuse you were talking about earlier. If you click this at the bottom, you can see, for a given configuration like MI355 on FP4, how much of the host cache—like the DRAM—is actually being used, and compare it with GB300 at the corresponding points on the curve.

1. The Capacity Bandwidth Tradeoff

Maybe dig into the point you were just making about the implications for DRAM. If we go back to the first big open-model release from a Chinese lab, DeepSeek taking the world by storm almost 2 years ago now, V3 and R1 came out, memory stocks sold off, and NVIDIA sold off. Everybody was really concerned that a more efficient model would mean less use of memory. But maybe the opposite is true: as you make models more efficient, you can increase concurrency and serve more users, so you still have just as much demand on the memory itself.

Could you put a finer point on the capacity-versus-bandwidth thing? A lot of our listeners may have tuned in for the conversation with Myron a few weeks ago, where we talked about the de-spec of the Rubin GPUs for Rubin Ultra, from a terabyte of GPU memory per GPU down to 192, matching the R200. That keeps the bandwidth the same but reduces the capacity. Can you explain the trade-off in the context of inference, where HBM bandwidth and capacity, as well as host DRAM bandwidth and capacity, are all used to serve users at a lot of points on this curve?

Wenyao Gao

I can start on the inference side. If we think about memory offloading and capacity, we definitely want to serve more users with more concurrency, because that maximizes aggregate output tokens. But we still need to think about the trade-off, which is the downside of offloading to DRAM: longer latency, especially long-tail latency.

We’ll customize based on different use cases. For example, we introduced another inference engine, TailRT, in our article. It focuses on low-latency cases. Essentially, it uses a megakernel for decode to reduce launch overhead, and in smaller-batch cases, such as batch size 1, it delivers blazing-fast decode speed, up to 470 tokens per second. The trade-off is that it can’t serve large batch sizes.

We’ve seen more and more inference engines trying to serve these special use cases on general-purpose GPUs rather than server products. People who want high interactivity and low latency will definitely love it. The trade-off really depends on how much you’re willing to pay and what kind of use cases you’re dealing with. If you’re Jane Street, you definitely want your request to get an output in several seconds. But if you’re a user like me, dealing with a normal agent task, I can just wait and maximize the output as long as the cost is affordable.

Jordan Nanos

You’re not using ultra-fast mode, Wenyao?

Wenyao Gao

No, I’m not using it. It’s too expensive. Also, it’s hard for me to feel the difference somehow.

Jordan Nanos

Yeah. Kimbo, how about you? Are you using ultra-fast on any of the coding agents right now?

Kimbo Chen

Not really. I don’t think I can even use fast right now, so, yeah.

Jordan Nanos

Okay, so what do you think about TailRT and the trade-offs there? Like Wenyao said, you’ve got to pay significantly more for that faster token speed. It’s a fun engineering problem, right? But maybe not a—

Kimbo Chen

Mm.

Jordan Nanos

—best thing that’s realistic.

Kimbo Chen

Back to what you were saying, Jordan, about the Rubin de-spec: keeping memory bandwidth and prioritizing that over memory capacity. I think that’s a good example of the design decisions we saw as well: memory bandwidth is more important than capacity. Concretely, sparse attention doesn’t help with memory capacity, and you still need memory bandwidth to sustain the performance you want.

In the ultimate speed-of-light performance, which we can see, in some sense, in TailRT or the ultra-low-latency regime, you’re fighting against how fast you can load your model or how fast you can load the relevant data to finish the relatively small amount of computation you have. In the ultra-low-latency regime, memory bandwidth is the most important part.

The problem with memory capacity is that we still need a lot of it, but dealing with insufficient memory capacity is a very standard problem in computer architecture. That’s why we have a cache hierarchy, and there are numerous ways, through hardware, to overlap computation with lower-tier, lower-bandwidth memory transfers. In Rubin’s de-spec, I think they’re betting on keeping the memory bandwidth while trying to connect GPUs through networking and, again, trying to overlap them.

2. Post Training Drives Capability

Jordan Nanos

Yeah. When Z.ai keeps the model architecture the same from 5.2 to 5.3 and gets such a performance improvement strictly from its post-training pipeline, what do you think they’re thinking about right now? Do you think they’re experimenting with even more efficiencies in future attention architectures, or are they just going to double down on DSA and keep it the same for some future GLM-6 release, or whatever comes next?

Kimbo Chen

My guess is they’d probably continue with the same architecture, pushing further for 5.x or maybe 5.4. But based on their releases, it seems like they’ll continue trying different architectures. Not too long after 5.3, they released 5.3 Flash, which isn’t really a Flash model. In my opinion, it’s almost like a Frankenstein model where they use KDA, or Kimi Delta Attention, with DSA, as far as I remember. They’re mixing all the efficient alternative attention mechanisms, putting them into a model, and actually training it. The model is pretty good, so I think its success could probably translate into a scaled-up version with even better capabilities and a similar architecture.

Jordan Nanos

Yeah. Let’s talk about the post-training pipeline. As a bit of a backdrop, before that, we can talk about the capabilities. The first time I remember people talking about this was a tweet from Tor Taxes[?], which got Elon to respond, and then got Jia Tang, the founder of Z.ai, to respond. The question was, “When do you think China’s going to get a Mythos-class model?” This was back in June, when GLM-5.2 had been out for a little while. Elon responded, “Probably Q1,” and Jie Tang said, “Won’t take that long.”

I made a comment on one of the episodes we recorded yesterday. I said to Dan, “To me, GLM-5.3 is a frontier cybersecurity model, because I get classified out of using the Anthropic or OpenAI models, even though we’re in the CVP threat-teaming program and we’re doing stuff with the neoclouds to help them do this. It’s not even the classifiers; it’s the stuff trained into the model that I can’t get around. So I fall back to using GLM-5.3, and I need to be more creative in my prompting if I want the frontier models not to refuse me and pollute the whole context window, where you have to rewind if you want to try anything again.”

Anyway, this is an incredibly capable coding model, especially for cybersecurity tasks, and it’s openly available. Anybody can download the weights. This isn’t the biggest model on the market, and all the improvements from 5.2 to 5.3 came through post-training. I kind of agree: just keep post-training going. What are the unique aspects of their post-training pipeline that you think are letting them do this?

Kimbo Chen

Yeah, just to comment on the tweet.

I think Jia Tang, the CEO, is pretty vindicated, right? It took only about a month after that. I can’t believe Elon got out-Elon’d by someone. It was an out-Elon timeline. The thing Elon is most known for—not the only thing, but the thing he’s most known for—is an aggressive timeline.

Jordan Nanos

Yeah.

Kimbo Chen

But, yeah, I think GLM-5.3—

Jordan Nanos

This is Mythos class right now—or Fable class—but it’s certainly approaching that. It’s nipping at their heels, getting pretty close, I’d say, right?

Kimbo Chen

Yeah, true. Technically, it’s definitely not Mythos class, but I think it’s still nontrivial to get Anthropic themselves to admit that 5.3 is—what do they call it?—Fable class, I think. Near Fable level.

Jordan Nanos

Let’s go find it. Yeah, good point. I’ll go find that—

Kimbo Chen

Yeah, so—

Jordan Nanos

—blog post from them.

Kimbo Chen

Yeah. I think it’s a nontrivial feat, all within a couple of months of post-training on the same model.

Among all the Chinese model labs, I’d say Z.ai is the one that invests most heavily in post-training and is really laser-focused on it. You can see other model labs changing their architectures every once in a while. GLM has stuck with the same architecture since GLM-5, despite DeepSeek already going through 2 iterations since DSA. Kimi has kept releasing new versions of its attention mechanisms over the past year and doing scale-up experiments. AntLing is doing all kinds of linear attention as well. StepFun is doing some very cool things, and MiMo is being even more conservative on that side.

GLM has mostly stuck with its architecture while focusing on post-training. The basic techniques in its post-training aren’t too far off from DeepSeek V3, which is still GRPO-based. But I think GLM’s post-training pipeline has very clear steps and reasoning behind how it adapts its algorithms to the efficiency it needs.

For example, in the first step, they use typical GRPO for general post-training. They do it synchronously to get the most stability out of training. After that, because they need to extract more system efficiency from training, and because agentic workloads typically have longer sequence lengths, they change approaches. GRPO—and RLVR in general—has always had the issue of a weak training signal. Roughly speaking, as your sequence gets longer, the strength of the reward signal gets diluted across the sequence.

Because of that, in the second stage, they switch to a more REINFORCE-like variant of a post-training algorithm that tolerates other system issues, such as policy staleness. That way, they can use an older version of the policy, or just the most recent version, instead of having to deal with a lot of importance-ratio and policy-staleness-related issues during calculation.

Jordan Nanos

Give me a quick summary. You’re describing algorithmic decisions here. These may be unique decisions they’ve made, but nothing I’ve heard you say before or during this talk would lead me to believe GLM-5.3 is doing something so unique algorithmically, or so completely different from the other labs, that they have a big advantage in terms of algorithmic work in the post-training pipeline. Is that fair to say?

Kimbo Chen

Yeah. I guess what I’ve said so far isn’t too unique to Z.ai. Yes, that’s correct.

Jordan Nanos

Okay.

Wenyao Gao

Actually, I wanted to say what I felt about GLM-5.3 when it first came out. It was completely based on post-training with the previous models, and I felt like it was a wake-up call for me. GLM-5.3’s agentic benchmark results improved by more than 10% just by doing post-training. It’s more GPU-efficient to do post-training than to pre-train a model from scratch.

I think that’s a wake-up call for a lot of other companies as well. They don’t have enough budget to train a model from scratch, but they still want to improve their company’s workflow in a specific area, and they happen to have proprietary, private data. They can just do post-training themselves and achieve a better result than some closed-source models.

If I remember correctly, GLM-5.3 was focused on agentic reasoning and general RL, and we can see that all 3 areas improved quite a lot in the benchmark results. When I saw the tweet that GLM-5.3 had come out, along with all the benchmark improvements, I was like, “No way. They did this just by post-training?” That’s quite amazing to me.

Jordan Nanos

Yeah. So—

Kimbo Chen

Yeah.

Wenyao Gao

Mm-hmm.

Jordan Nanos

Yeah, go, Kimbo.

Kimbo Chen

I totally agree with Wenyao about how much juice there is left to squeeze just by post-training. 5.3’s post-training effort is definitely very impressive. In our article, we also compared GLM-5.3’s cybersecurity capabilities with 5.2, and the difference is really notable. It’s a night-and-day capability difference, and that’s all just post-training.

To be fully honest, GLM hasn’t released a detailed technical report since GLM-5, so I’m working from conversations with researchers and their blog announcements. I think there are 2 things that are most notable. One is the research they published about doing PPO-style training. In some sense, they’re reverting to the typical RL training format, with a critic model grading rollouts along the way and co-training the critic model with the actor—the main model. They call it Single-Rollout Asynchronous Optimization, or SAO.

The second thing is that, in their public speeches and at conferences, they talk a lot about—thanks for putting up the meme, by the way.

Jordan Nanos

Take the meme.

Kimbo Chen

They talk a lot about—thanks. I don’t know; it’s probably too Taiwanese, too local. Even my Chinese friends—the SLIME authors and people in the Chinese community—don’t understand that meme, unfortunately.

Wenyao Gao

Maybe explain that a bit, Kimbo. It’s so funny.

Kimbo Chen

Wenyao, have you watched Sword Art Online?

Wenyao Gao

No, I haven’t, but I saw your explanation on Slack. That was fun.

Jordan Nanos

Do they understand this meme, Kimbo? “10:15,” something like that.

Kimbo Chen

I don’t know. I haven’t asked anyone about that yet.

Jordan Nanos

Okay. I jumped in earlier and said something that might get misconstrued here: that they didn’t have—

Kimbo Chen

Mm.

Jordan Nanos

—necessarily super-unique advancements in algorithms. You just said the word SLIME, which I was waiting for. There’s both the Single-Rollout Asynchronous Optimization, but then also all the infrastructure work related to training efficiency. That seems to me like it allows them to run a lot more experiments, potentially many more jobs, and potentially much more compute-efficient jobs. That’s itself an advancement that sets them ahead of anybody with equivalent or even more compute who just can’t do as much research as them.

Kimbo Chen

Yeah, definitely. SLIME is highly regarded in the open-source community. It’s arguably one of the best-designed post-training frameworks, if not the best. I’m sure they have very good infrastructure to support that.

Z.ai also released an article, I think probably not too long ago—about 2 weeks ago—on how they use their models to collaborate with one another and further improve system efficiency. That includes bringing up and verifying GPU kernels for their crazy GLM-5.3 Flash model on unfamiliar hardware with a different architecture. I’m not sure exactly what the hardware was, but it wasn’t a GPU. They use their models to improve that, and they have ways to improve the improvement loop and monitor system-level jobs to squeeze more efficiency out of the whole infrastructure.

So, yeah, I think SLIME is definitely notable. Algorithmically, SAO is a clear innovation, applied in 5.2 and 5.3, alongside the infrastructure work, even just based on what they’ve open-sourced.

It’s a very good improvement and definitely would help—

Jordan Nanos

Yeah.

3. Training Across Chinese Hardware

And let me throw one thing in here that I think a lot of people have missed, or that I’ve at least been focused on. If we go back to the GLM-5 paper—

Kimbo Chen

Mm-hmm.

Jordan Nanos

I want to read a paragraph from this. Remember, this is almost a year old at this point. They say, “Last, one more technical contribution lies in the fact that from the first day, GLM-5 is full-stack adapted to Chinese GPU ecosystems. We have successfully completed deep optimization, spanning from underlying kernels to upper-level inference frameworks across seven mainstream domestic chip platforms, including Huawei Ascend, Moore Threads, Hygon, Cambricon, Kunlunxin, MetaX, and Enflame.”

When you’re talking about the model helping bring up the infrastructure for serving GLM-5, it’s not necessarily just Nvidia GPUs, kernels, and the serving stack for SGLang on the AMD or Nvidia GPUs that we test in InferenceX. They’re serving this model, at least they claim, for many months on seven different domestic Chinese accelerators. What do you guys make of that?

Kimbo Chen

First of all, they also publicly claimed that GLM-5.3 Flash, under the name OxAlpha, is fully served on Chinese hardware. I remember when people tested it, they saw OxAlpha performing very well while also being able to serve, I think, 100 trillion tokens or something—a ridiculous amount of tokens compared to what you’d expect.

Based on the number of tokens they can serve for free, people thought it was impossible that it was being served on GPUs by a Chinese lab, because Chinese labs aren’t that GPU-rich. But it turns out they’re using Chinese hardware. Assuming everyone’s honest, I think they’re able to plow through all the blockers—the basics of the kernels, the systems, everything—and serve those models efficiently.

Jordan Nanos

Yeah. I’ve got it on screen. OxAlpha was a stealth model on OpenRouter. It was only a month and a half ago, on August 20, when this happened. It feels like a while ago now, much longer. But anyway, things move fast.

Kimbo Chen

Yeah, they did. I think they brought it up in 1 or 2 months. They released GLM-5.3 in early August, and then GLM-5.3 Flash in late August.

Jordan Nanos

Yeah.

Kimbo Chen

So that means that even if we try to bound when they started developing the GLM-5.3 Flash model, it probably wasn’t too long—more like 2 or 3 months, as far as I can tell. Betting on KDA was still a big bet before Kimi K3 came out, because no one really knew whether KDA scaled that well. I think Kimi K3 came out in mid-July.

Jordan Nanos

Yeah.

Kimbo Chen

So the most aggressive timeline would be that they trained GLM-5.3 Flash within 2 months. If that’s true, that’s actually pretty crazy.

Wenyao Gao

Yeah, it is really crazy.

Kimbo Chen

One thing I want to add about the hardware side is that I think I also wrote about it in the article. We can make a guess. First of all, the arithmetic intensity of the attention operation during decode is typically matched with the arithmetic intensity of the hardware. This is shown most notably in DeepSeek V3, which DeepSeek talks about openly.

That means there’s some sort of hardware and software co-design: you try to change the model configurations to fit the hardware properties of the GPUs you serve on. DeepSeek fitted its model for H800s. That got me curious, so I tried to calculate the number for GLM-5. One of the most interesting changes they made is to the number of heads. I can’t remember the exact configurations they changed, but because of those changes, the arithmetic intensity is very different from that of Nvidia GPUs—

Jordan Nanos

Yeah, I’m pulling this up here.

Kimbo Chen

Yes, thank you. I think my calculation was somewhere around 120 for GLM-5, or the 5.x-series models. I did some basic calculations, and it seems to fit with Moore Threads GPUs. That’s somewhere in the range.

That doesn’t prove they’re optimizing for that. It doesn’t prove that Z.ai is actually serving models on that hardware, or that the models are optimized for it. But I think it at least shows something. My conspiracy theory is that they’re probably optimizing for it, but I couldn’t get confirmation. So, Z.ai, if you’re watching this, I’d love to hear your thoughts.

Wenyao Gao

We are high alpha here.

Kimbo Chen

Yeah, but at least I think what we can—

Wenyao Gao

Led by Kimbo.

Kimbo Chen

Yeah, we can calculate the arithmetic intensity, right? But I think it at least shows that they’re definitely optimizing for something else, or they’re sacrificing quite a lot of software-hardware optimization for other reasons that aren’t public. Obviously, it wouldn’t work well on—or wouldn’t be optimal for—B200s or even H200s.

Jordan Nanos

Yeah. It’s a sign of what’s to come: somebody might make a software-level co-design decision based on hardware that isn’t Nvidia GPUs. I think that’s quite a big statement.

Wenyao Gao

Mm-hmm. Yeah. And adding to that, as the models’ capabilities improve, we’re beginning to see the R&D cycle shorten drastically, right? Take kernel development as an example. Nowadays, agents can write kernels that perform much better than humans, with the proper tools, like a kernel development agent or Cake, which was just released recently, and the right harness and tools.

We also have leaderboards for agent-written kernels. As long as you have the budget, an agent will write a faster kernel than a human. It’s pretty interesting to see how different model companies will compete with each other with the help of agents. It’s human plus AI competing.

Jordan Nanos

How many tokens do you think the AMD TileRT megakernel for GLM-5.3 cost them to produce?

Wenyao Gao

It must be a lot, I think. What do you think, Kimbo?

Kimbo Chen

I don’t have a good idea, honestly. I wonder. Maybe we should ask.

Jordan Nanos

Yeah, maybe we should. We’re coming up with good ideas here. Okay, guys, is there anything you think we’ve missed talking about? I think we went through InferenceX’s performance results, some high-level discussion about the cyber capabilities of this model, what we’re using it for, high sparsity, high cache, KV offloading, model architecture, and the post-training pipeline.

What else is left? Rumors and vibes about what’s to come with GLM-5.4? What do you want to speculate about as we sign off?

Kimbo Chen

Yeah, I think we briefly talked about it. GLM-5.3-Flash is definitely a success for them. They’re able to mix DSA with KDA, using a very new architecture while still having a very good model with great capabilities. I suspect they can scale up the GLM-5.3-Flash model architecture to the size of GLM-5.3, and probably squeeze out even more performance or model capabilities.

GLM-5.3-Flash has that crazy efficiency as well, right? It uses linear attention and sparse attention.

Wenyao Gao

I’m curious about what they’re going to do next, because GLM will definitely explore something else. Through post-training, they show us that you can improve model capability not only by scaling up, but also by squeezing more out of your current parameter size. Even if you don’t have a trillion-parameter model, you can still perform as well. For companies that do inference for the model and are highly sensitive to cost, I think it will definitely be a good call.

We’ve seen Harvey in the Bay Area with its own post-trained agent based on a Kimi model. We also see Periodic Labs—maybe Kimbo can expand on that—doing post-training for AI for science. I’m really excited to see how this trend goes, and especially what GLM-5.4 will bring us.

Kimbo Chen

One last thing about post-training that’s important but not discussed very much—and Z.ai isn’t willing to clarify it further—is human effort. In their public conferences, they talked about spending a lot of human effort on, supposedly, data when training GLM-5.2 and GLM-5.3.

The question is, what kind of human effort? I’m pretty sure it’s related to data labeling, but what kind of data labeling, and what kind of effort goes into it? I think that’s also pretty important when it comes to post-training: being able to get quality data.

Jordan Nanos

Makes sense. So what do you think comes next? Do you think we get SpaceBunny Alpha, MiniMax, and 3.1 Flash? Do you think it’s GLM? Do you think Kimi comes out with something new? DeepSeek? We had a big release from Reflection AI.

I don't know. What are you guys looking forward to most with the model releases coming out soon?

Wenyao Gao

I'm looking for an efficient model. Actually, Reflection's model is really efficient. I'm thinking maybe in the future we'll have large models, right? Two trillion, three trillion, capable enough for people to do powerful stuff.

But we'll also have models that offer good enough performance and are extremely efficient, so companies won't care about their cost and can still do certain things well, like the models Reflection releases.

Jordan Nanos

Makes sense, guys. Okay, well, thanks for coming on. It's been a whirlwind tour of everything GLM-5.3, why we don't think model releases like this mean people should sell their memory stocks, and why we expect Jevons paradox to continue to result in more people consuming a lot more tokens, a lot more HBM, and a lot more bandwidth over time. Thanks for joining, guys. Great job.

Kimbo Chen

Thank you, Jordan. Thank you, Wenyao.

Wenyao Gao

Thank you, Jordan. Thanks, everybody.