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[GH-ISSUE #28] [Question] On NVLink bandwidth of H800 #22

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opened 2026-10-26 21:11:11 +00:00 by bsakaguchi · 5 comments
bsakaguchi commented 2026-10-26 21:11:11 +00:00
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Originally created by @GHGmc2 on GitHub (Dec 30, 2024).
Original GitHub issue: https://github.com/deepseek-ai/DeepSeek-V3/issues/28

NVLink offers a bandwidth of 160 GB/s, roughly 3.2 times that of IB (50 GB/s).

May I know why the bandwidth of NVLink on H800 is 160GB/s, instead of 400GB/s?

Thanks.

Originally created by @GHGmc2 on GitHub (Dec 30, 2024). Original GitHub issue: https://github.com/deepseek-ai/DeepSeek-V3/issues/28 > NVLink offers a bandwidth of 160 GB/s, roughly 3.2 times that of IB (50 GB/s). May I know why the bandwidth of NVLink on H800 is 160GB/s, instead of 400GB/s? Thanks.
bsakaguchi commented 2026-10-26 21:11:13 +00:00
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@mowentian commented on GitHub (Dec 31, 2024):

400GB/s 是双向理论值，160GB/s 是我们的单向实测

<!-- gh-comment-id:2566274367 --> @mowentian commented on GitHub (Dec 31, 2024): 400GB/s 是双向理论值，160GB/s 是我们的单向实测
bsakaguchi commented 2026-10-26 21:11:13 +00:00
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@GHGmc2 commented on GitHub (Jan 1, 2025):

400GB/s 是双向理论值，160GB/s 是我们的单向实测

谢谢。那IB带宽50GB/s也是单向实测值吗？

<!-- gh-comment-id:2566837055 --> @GHGmc2 commented on GitHub (Jan 1, 2025): > 400GB/s 是双向理论值，160GB/s 是我们的单向实测 谢谢。那IB带宽50GB/s也是单向实测值吗？
bsakaguchi commented 2026-10-26 21:11:14 +00:00
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@yiakwy-xpu-ml-framework-team commented on GitHub (Jan 1, 2025):

400GB/s 是双向理论值，160GB/s 是我们的单向实测

Could I get the nccl test snapshot (both algorithm and bus bandwidth) of all to all test with multiple nodes ? If the bandwidth data (160 GB/s) is from nccl-test, it hardly to be true. H800 should have the same IB/NCCL performance with H100 (450-490 GB/s) (NV SHARP)

<!-- gh-comment-id:2567041169 --> @yiakwy-xpu-ml-framework-team commented on GitHub (Jan 1, 2025): > 400GB/s 是双向理论值，160GB/s 是我们的单向实测 Could I get the nccl test snapshot (both algorithm and bus bandwidth) of all to all test with multiple nodes ? If the bandwidth data (160 GB/s) is from nccl-test, it hardly to be true. H800 should have the same IB/NCCL performance with H100 (450-490 GB/s) (NV SHARP)
bsakaguchi commented 2026-10-26 21:11:14 +00:00
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@shenh10 commented on GitHub (Feb 6, 2025):

400GB/s 是双向理论值，160GB/s 是我们的单向实测

谢谢。那IB带宽50GB/s也是单向实测值吗？

同问。IB connect X-8 单向 400Gb/s （50GB/s）像是用的理论值。 @mowentian

<!-- gh-comment-id:2639606198 --> @shenh10 commented on GitHub (Feb 6, 2025): > > 400GB/s 是双向理论值，160GB/s 是我们的单向实测 > > 谢谢。那IB带宽50GB/s也是单向实测值吗？ 同问。IB connect X-8 单向 400Gb/s （50GB/s）像是用的理论值。 @mowentian
bsakaguchi commented 2026-10-26 21:11:15 +00:00
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@renwuli commented on GitHub (Mar 5, 2025):

400GB/s 是双向理论值，160GB/s 是我们的单向实测

可以分享一下您的单向实测脚本吗？

<!-- gh-comment-id:2699932354 --> @renwuli commented on GitHub (Mar 5, 2025): > 400GB/s 是双向理论值，160GB/s 是我们的单向实测 可以分享一下您的单向实测脚本吗？
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