From: lkcl <lkcl@web>
Date: Sat, 8 Apr 2023 10:40:25 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls012_v1~77
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=c819f8562f9efd63a4591669b94582d769537cd3;p=libreriscv.git

---

diff --git a/openpower/sv/rfc/ls012.mdwn b/openpower/sv/rfc/ls012.mdwn
index 395863cf2..cae948fb4 100644
--- a/openpower/sv/rfc/ls012.mdwn
+++ b/openpower/sv/rfc/ls012.mdwn
@@ -82,6 +82,20 @@ where IEEE754 full bit-accuracy is paramount.  In 3D GPU scenarios for example
 even 12-bit accuracy can be overkill, but for HPC Scientific scenarios 12-bit
 would be disastrous.
 
+There are a **lot** of operations here, and they also bring Power ISA
+up-to-date to IEEE754-2019.  Fortunately the number of critical instructions
+is quite low, but the caveat is that if those operations are utilised to
+synthesise other IEEE754 operations (divide by `pi` for example) full bitlevel
+accuracy (a hard requirement for IEEE754) is lost.
+
+Also worth noting that the Khronos Group defines minimum acceptable bit-accuracy
+levels for 3D Graphics: these are **nowhere near* the full accuracy demanded
+by IEEE754, the reason for the Khronos definitions is a massive reduction often
+four-fold in power consumption and gate count when 3D Graphics simply has no need
+for full accuracy.
+
+*For 3D GPU markets this definitely needs addressing*
+
 ## Audio/Video
 
 Found at [[sv/av_opcodes]] these do not require Saturated variants because Saturation