More Details On The Proposed Simple-V Extension To RISC-V For GPU Workloads

Written by Michael Larabel in RISC-V on 4 January 2019 at 05:44 AM EST. 9 Comments
With the proposed Libre RISC-V Vulkan accelerator aiming to effectively be an open-source GPU built atop the open-source RISC-V ISA there were recently some new details published on how the design is expected to work out.

For this very ambitious libre RISC-V SoC design. that EOMA68 developer Luke Kenneth Casson Leighton wants to pursue through crowdfunding, it's just not a matter of spinning his own RISC-V design but for making the SoC suitable for GPU workloads he has talked of a "Simple-V" extension he envisions.

Over the holidays he shed more light on this Simple-V extension he wants to develop for RISC-V that he thinks could make it more suitable for GPU performance. Keep in mind, it's looking like this hypothetical SoC will just be around a 64-bit quad-core 800MHz part.

Simple-V in effect is: "mark ordinary registers as “vectorised,” and when an instruction uses one such “tagged” register, go into a hardware-unrolled version of a software macro loop, issuing otherwise identical instructions with contiguous sequentially-increasing register numbers."

But even with Simple-V, the initial performance target for this SoC/GPU should it reach production is 25 FPS @ 720p and around 5~6 GFLOPs compute power.

For those wishing to learn more about the planned very low-level, technical details of Simple-V can do so via this blog post.

L.K.C.L. also commented that he is pursuing an "ethical" design to the GPU/SoC:
The project is being run along ethical lines. That in particular means unanimous decision-making. Nobody gets to over-rule anyone else: everyone matters, and everyone’s input matters. So if I think Tomasulo is better, it’s up to me to keep on researching and evaluating and reasoning until I have convinced everyone else… or they have convinced me otherwise.

I have it on good authority from some extremely comprehensive research that this is a hell of a lot better way to do decision-making than “mob-rule” voting. “Mob-rule” voting (a.k.a. “democracy”) basically automatically destroys the morale and discounts the will of the “minority.” No wonder democratic countries have minority representation political groups, because it’s heavily brainwash-ingrained into people living in such countries that the minority view shall be disregarded; of course they feel the need to shout and get angry!
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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