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


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Back again.

 

Some of the users have been asking why the "Errata Fix" feature doesn't work (i.e. "Fix required" stated even after the Fix button has been pressed). The feature itself is working fine, however I forgot to add a check in the GUI. Also some claims that the software is wrong when it states that the microcode is outdated has emerged.

 

So:

 

A small update: Bulldozer Conditioner R1.01B

 

Original package checksum (MD5): C3C4E3492B3FBFE1079AE5D57C25172B

 

Changes:

 

- Added a hardware flag to indicate that the errata has been fixed.

- Changed the way how the software is accessing the cores, the tasks are completed quicker than before

- An APU specific bug fixed

- Added information about the most recent microcode and AGESA versions under Info menu.

- Some small changes to the GUI

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Back again.

 

Stilt, can you explain, what exactly your patch is doing? I suppose, you write some values into some MSR's to manage low-level fixes and bug workarounds, that have been inserted in the microcode by the BIOS/AGESA on boot. Switching these off may speed up something, but it's dangerous, if the (originally patched) hardware flaw haven't been fixed yet. And what are this fixes? In particular, that is NRAC, TBM («trailing bit manipulation» instructions?) and Stack Special? Officially, Bulldozer (all steppings and revisions) doesn't have TBM, but Piledriver does.

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The actual technical background is under investigation currently.

 

Until then, I can only speculate and assume:

 

By default a x87 FP instruction is blocked / partially blocked.

When the "blockade" is removed (BDC "NRAC": Enabled to Disabled), SuperPI which heavily utilizes this instruction receives a massive boost.

 

It is not a post tape-out workaround.

Neither AGESA or µCode control this feature, all of the post tape-out workarounds (errata) are controlled by these two.

 

If it was something that was actually broken, it would have been fixed in Piledriver and beyond.

 

A software doesn't go much more unofficial than BDC does.

It should be used for testing purposes ONLY.

Obviously it shouldn't be used in systems which can be considered 'critical'.

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By default a x87 FP instruction is blocked / partially blocked. When the "blockade" is removed (BDC "NRAC": Enabled to Disabled), SuperPI which heavily utilizes this instruction receives a massive boost.

 

What instruction? There is no «NRAC» in the original x86 or any of its additions (including x87). Besides, if some code uses any blocked or unavailable instruction, the CPU should generate #UD or other exception. So, it must be either microcode workaround for a HW bug or some other explanation.

 

If it was something that was actually broken, it would have been fixed in Piledriver and beyond.

 

Well, then there is no reason for keeping it that way for 2 core generations, if it just slows things down.

 

And you haven't answered about other fixes in your program.

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A small update: Bulldozer Conditioner R1.02B

 

Original package checksum (MD5): BCC929498EF1B01B7F99B8F2DA805F46

 

Bulldozer Conditioner R1.02B

Mirror: http://downloads.hwbot.org/downloads/tools/BDC_R1.02B.zip

 

Changes:

 

- Enhanced the NRAC fix

- Added a UAC prompt (admin rights) for Windows Vista / 7 & 8.

- Updated the AGESA version info

 

The enhanced fix included in BDC R1.02B is around 10 seconds faster in SuperPI 32M than the one in R1.00 / R1.01 versions ;)

Edited by Massman
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