Add links to C libraries and rationale for changing direction on the project goals

diff --git a/docs/pypowersim.mdwn b/docs/pypowersim.mdwn
index 33d0c5a2af22b67c950c97a1299763f3dae246b3..6596417844f8b65ca4431248ddbc36292358d7e0 100644 (file)
--- a/docs/pypowersim.mdwn
+++ b/docs/pypowersim.mdwn
@@ -199,3 +199,18 @@ $ cmp out0 data/audio/mp3/mp3_0_data/samples0
 ```
 
 As is usual for UNIX commands no output indicates the files are identical.
+
+# Appendix - Historical notes for design decisions, and further work
+
+As originally conceived, the goal of the project was to deliver a high-performance
+user space simulator of the scalar POWER ISA and our SVP64 vector extension. A
+high-performance C-based  RISC-V simulator,
+[Cavatools](https://www.bsc.es/research-and-development/software-and-apps/software-list/cavatools),
+was chosen as a base. Later on, as a measure of the needed funds and skills become 
+clear, a change of scope was adopted. Instead, our new goal was to extend and 
+improve our own existing reference Python simulator, with those instructions. 
+However, as much as possible was *done in C*. A 
+[*C* based Power ISA decoder](https://git.libre-soc.org/?p=openpower-isa.git;a=tree;f=src/libopid;h=db1fd8fcd01ea4c002bdd75da181ae24ee6f5fa8;hb=refs/heads/libopid)
+(as a general-purpose library) and a
+[Pseudo-code to C compiler](https://git.libre-soc.org/?p=openpower-isa.git;a=tree;f=src/openpower/oppc;h=927f670065ea84b4ed0d53d7062b32b011507738;hb=refs/heads/oppc)
+were written. This means that a competent team can take our work and complete a C-based Cavatools port.