The Book of Bulldozer - Revelations: Episode 2 (SuperPI / x87)

[The Stilt]

There are two kind of news bad and good ones.

Let's get rid of the bad ones first:

Originally I tested this fix on three different CPU/APUs (Richland, Trinity and Vishera).
When I went to verify the effects of the fix on Zambezi the system crashed immediately once the necessary changes were written.

After some research I noticed that these registers do not respond on Zambezi based CPUs.
Upon reading all of them return null values and crash the system unless a special method is used.
At first it appeared that these registers do not exist on Zambezi, however after digging a bit deeper I found indication that the registers are there... But for some reason AMD seem to have protected them with a ESI/EDI password on Zambezi.

They do not require any passwords on any Piledriver based APU/CPU.

So the fix will not be available for Zambezi users.
Sorry for the massive let-down

The the good news:

The software is pretty much finished.
It should be available for download within this week.

After the let-down on Zambezi I felt that something had to be done for Zambezi too.
While it does not result as massive boost as the original fix does it still gives something:

SuperPI 1M: > 1 second improvement
SuperPI 8M: > 10 second improvement
SuperPI 32M: > 35 second improvement

It is called as "Zambezi Stack Special (PD)".
Note: There might also be some performance retardation in some applications when enabled (Zambezi vs. Vishera effect).

Zambezi is significantly faster than Vishera in SuperPI by default so the difference between a "fixed" Vishera and a tuned Zambezi won't be that massive after the "Zambezi Stack Special" configuration.