On Wed, 13 May 2020 21:52:34 +0200 Paul Boddie paul@boddie.org.uk wrote:
On Tuesday 12. May 2020 19.20.37 Christopher Havel wrote:
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(1) Why are there none of these OSHW devices using existing x86-compatible CPUs/SoCs?
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(2a) Are there any meaningful barriers to creating an OSHW-compatible x86 CPU/SoC, independent of major chip houses (Intel, AMD) or established niche players (VIA, etc)?
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(2b) I've heard noises of a homegrown sort of effort out of China, from a company and fab house over there... could that CPU be considered as an acceptable candidate for such an effirt, and if not, why...? (I assume not, and because "China!", but I'm wide open here.)
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The Chinese have a deal with Via which bought out Cyrix which had been in a patent ware with Intel as they used hard-coded instructions whereas Intel and AMD used micro-code to decode instructions. https://www.youtube.com/watch?v=iWGAdoMz1c0
As to why there are no competitors in the X86 space, the amd64 64-bit extensions are patented AFAIK. So you're limited to a 32 bit system. That's not to mention MMX, SSE, AVX, and an assortment of other instructions throughout the years.
Then there's the amount of design you have to do just for the instruction set. Its hysterical how many instructions for moving data there are. https://www.youtube.com/watch?v=g9_FYRAfyqQ
Then you need something with high enough speed to match or exceed the speed of the competition, without voiding any of their patents, which is something they can't even achieve.
Then you need to create masks for the lithography for fabricating these chips. Luke says a small opensource RISC-V CPU would cost millions to create the masks for on an old node -- 32nm IIRC. 7nm costs double the amount that 16nm costs for chip fabrication according to AMD which places it in the hundreds of millions for the masks; and you need more for 7nm then previous nodes.
You also have to have really good power usage, as 7nm is so small that you have almost no space left for thermal conductivity. In fact, current AMD offerings are thermally limited in the silicon. They could clock higher and use more power but they'd blow through their thermal envelope.
Also, according to AMD, "extreme" measures must be taken to see to it that clock speeds remain high instead of going lower then previous offerings.
You need to have enough transistors per mm2.
You need enough cores, memory channels, and PCIe 4.0 lanes.
In summery:
What you should be asking is, "Why are there no OSHW CPUs/GPUs for purchase by consumers at all?"
In short, the Parallela board used a Xilinx (closed source HW and SW), FPGA for their Epiphany CPU and said that they couldn't make it in silicon due to lack of demand coupled with expense. When people demand OSHW, they will get it. Until then, its going to be based solely on the kindness of the companies and developers, like luke. Gooooooo Luke!!!
Sincerely, David