From: lkcl Date: Thu, 5 May 2022 16:06:56 +0000 (+0100) Subject: (no commit message) X-Git-Tag: opf_rfc_ls005_v1~2439 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=6528183afed7f01c013d723a5beaf5f261c9bea9;p=libreriscv.git --- diff --git a/openpower/sv/SimpleV_rationale.mdwn b/openpower/sv/SimpleV_rationale.mdwn index 1552a12a8..4b843a0f5 100644 --- a/openpower/sv/SimpleV_rationale.mdwn +++ b/openpower/sv/SimpleV_rationale.mdwn @@ -17,7 +17,27 @@ multiple billion-dollar-revenue companies, to sustain them. Therefore it begs the question, why on earth would anyone consider this task? -Hints as to the answer emerge from an article +First hints are that whilst memory bitcells have not increased in +speed since the 90s (around 150 mhz), increasing the datapath widths +has allowed significant apparent speed increases: 3200 mhz DDR4 and +even faster DDR5, and other advanced Memory interfaces such as HBM, +Gen-Z, and OpenCAPI, all make an effort, but these efforts are +dwarfed by the two nearly three orders of magnitude increase in +CPU horsepower. Some systems at the time of writing are approaching +a *Gigabyte* of L4 Cache, by way of compensation. + +Efforts to solve this problem by moving the processing closer to +or directly integrated into the memory have traditionally not gone +well: Aspex Microelectronics, Elixent, these are parallel processing +companies that very few have heard of, because their software stack +was so specialist that it required heavy investment by customers to +utilise. D-Matrix and Graphcore are a modern incarnation of the exact +same "specialist parallel processing" mistake, betting heavily on +AI with Matrix and Convolution Engines that can do no other task. +Aspex only survived by being bought by Ericsson, where its specialised +suitability for massive wide Baseband FFTs saved it from going under. + +Second hints as to the answer emerge from an article "[SIMD considered harmful](https://www.sigarch.org/simd-instructions-considered-harmful/)" which illustrates a catastrophic rabbit-hole taken by Industry Giants ARM, Intel, AMD,