points
8 days ago
| 1 comment
| HN
RISC-V is still at the point where open-source implementations (in rtl) are faster than purchasable proprietary ones (in silicon).

XiangShan is currently the fastest open-source CPU implementation: https://github.com/OpenXiangShan/XiangShan

uarch slides: https://tutorial.xiangshan.cc/hpca25/slides/20250302-HPCA25-...

uarch slides with WIP features: https://tutorial.xiangshan.cc/micro25/slides/Microarchitectu...

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kragen
8 days ago
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Do you expect that to change at some point?
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camel-cdr
8 days ago
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Yes, but keep in mind that I'm purposfully comparing development RTL on the open-source side with finished silicon product on the proprietary side.

Many companies have production ready/fully verified IP that are much faster than XiangShan, but they haven't taped out and productized it yet.

E.g. Tenstorrent Ascalon IP is available and at 21 SPECint2006/GHz. They want to release a lower clocked devboard on TSMC 12nm in 2026 Q2.

XiangShan is currently at 15 SPECint2006/GHz, but are targeting 22 SPECint2006/GHz in the next iteration, that is currently in the works. Well have to see who gets there first.

The inherent gap between RTL design and final product may be large enough that open-source RTL can keep up in terms of IPC, if XiangShan continues their momentum. But I think open-source trailing 1-3 years is a more realistic long term outcome.

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rwmj
8 days ago
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I've just seen a demo of a very high performance RISC-V chip (actual silicon) that'll blow the doors off other implementations. Under NDA of course.

Actually available for pre-order, take a look at the UltraRISC DP-1000 (unrelated to the chip above).

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kragen
8 days ago
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Excellent! But probably open-source implementations will also continue to improve.
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0x000xca0xfe
8 days ago
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Can you share any details? Like potential year of release?
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rwmj
8 days ago
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That's actually the most NDA thing, since companies don't want to be held to a release date. However the fact they have fully functional engineering samples running in their offices now is very encouraging.
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