From: lkcl <lkcl@web>
Date: Wed, 29 Mar 2023 13:50:21 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls001_v3~8
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=33a200d9298962244e532d1b6e04c7ae6c677ac6;p=libreriscv.git

---

diff --git a/openpower/sv/rfc/ls010.mdwn b/openpower/sv/rfc/ls010.mdwn
index e30326f2b..dfabbaeef 100644
--- a/openpower/sv/rfc/ls010.mdwn
+++ b/openpower/sv/rfc/ls010.mdwn
@@ -42,7 +42,37 @@ svp64 fits into the "reserved" portions of the v3.1 prefix, making it possible f
 
 Subset implementations in hardware are permitted, as long as certain
 rules are followed, allowing for full soft-emulation including future
-revisions.  Details in the [[svp64/appendix]].
+revisions.  Compliancy Subsets exist to ensure minimum levels of binary
+interoperability expectations within certain environments.
+
+## Register files, elements, and Element-width Overrides
+
+In the Upper Compliancy Levels the size of the GPR and FPR Register files are expanded
+from 32 to 128 entries, and the number of CR Fields expanded from CR0-CR7 to CR0-CR127.
+
+```
+    #pragma pack
+    typedef union {
+        uint8_t  b[];
+        uint16_t s[];
+        uint32_t i[];
+        uint64_t l[];
+        uint8_t actual_bytes[8];
+    } el_reg_t;
+
+    elreg_t int_regfile[128];
+```
+
+Hardware Architectural note: to avoid a Read-Modify-Write at the register file it is
+strongly recommended to implement byte-level write-enable lines exactly as has been
+implemented in DRAM ICs for many decades. Additionally the predicate mask bit is advised
+to be associated with the element operation and ultimately passed to the register file.
+When element-width is set to 64-bit the relevant predicate mask bit may be repeated
+eight times and pull all eight write-port byte-level lines HIGH. Clearly when element-width
+is set to 8-bit the relevant predicate mask bit corresponds directly with one single
+byte-level write-enable line.  It is up to the Hardware Architect to then amortise (merge)
+elements together into both PredicatedSIMD Pipelines as well as simultaneous non-overlapping
+Register File writesto achieve High Performance designs.
 
 ## SVP64 encoding features