[GTALUG] How to go fast without speculating... maybe

David Collier-Brown davec-b at rogers.com
Mon Jan 29 21:56:41 EST 2018

On 29/01/18 09:17 PM, Alvin Starr via talk wrote:
> A number of groups have tried to develop extremely parallel processors 
> but all seem to have gained little traction.
> There was the XPU 128, the Epiphany(http://www.adapteva.com/) and more 
> recently the Xenon Phi and AMD Epyc.
> At one point I remember reading a article about sun developing an 
> asynchronous CPU which would be interesting.

Many experiments of that era fell flat, as did the attempt at at an 
async Sun.

> All these processors run into the same set of problems.
>     1) x86 silicon is amazingly cheap.
>     2) supporting multiple CPUs cause more software support for each 
> new CPU architecture.
>     3) very little software is capable of truly taking advantage of 
> many parallel threads without really funky compilers and software 
> design tools.
>     4) having designed a fancy CPU most companies try very hard to 
> keep their proprietary knowledge all within their own control where 
> the x86 instruction set must be just about open source now days.
>     5) getting motherboard manufacturers to take a chance on a new CPU 
> is not an easy thing.
> My benchmark for processor success is: Does several of 
> Asus,Supermicro,Tyan,Gigabyte et al make a motherboard for this CPU.
> Even people with deep pockets like DEC with their Alpha CPU and IBM 
> with their Power CPUs have not been able to make a significant inroad 
> into the commodity server world.
> Mips has had some luck with low to mid range systems for routers and 
> storage systems but their server business is long gone with the death 
> of SGI.
> Sun/Oracle has had some luck with the Sparc but not all that much 
> outside their own use and I am just speculating but I would bet that 
> Sun/Oracle sells more x86 systems than Sparc systems.

All those companies, plus H-P, hit critical mass: people ported their 
software to them.  Without that, you're
stuck with x86 supersets. And if you don't keep succeeding, customers 
defect to the competition.

Oracle fell off the table a few years back, recognized it and laid off 
their Solaris team. Their present is x86 and Fujitsu SPARC, and their 
future is purpose-built x86 with hyperchannel.

> ARM seems to be having some luck but I believe that luck is because of 
> their popularity in the small computer systems world sliding into 
> supporting larger systems and not by being designed for servers from 
> the get go.
> I am a bit of a processor geek and have put lots of effort in the past 
> into elegant processors that just seem to go nowhere.
> I would love to see some technologies other than the current von 
> Neumann somewhat parallel SMP but I have a sad feeling that that will 
> be a long time coming.
> With the latest screw-up from Intel and the huge exploit surface that 
> is the Intel ME someone may be able to get some traction by coming up 
> with a processor that is designed and verified for security.

Compilers folks have given up on software-only magic: the T1/T5 showed 
that hardware could contribute greatly,  and I suspect hardware-software 
co-design may be the next thing we see. A more secure non-speculative 
processor might suffice, but I don't know if it will be based on SPARC, 
POWER or something resembling an x86 microcode will be most attractive 
to the market.

I do know it will run Linux.

> On 01/29/2018 05:36 PM, David Collier-Brown via talk wrote:
>> Kunle Olukotun didn't like systems that wasted their time stalled on 
>> loads and branches. He and his team at Afara Websystems therefor 
>> designed a non-speculating processor that did work without waits. It 
>> became the Sun T1.

David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb at spamcop.net           |                      -- Mark Twain

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