The Stilt releases utility to enable x87 instructions on AMD chips

Finland based LN2 overclocker ‘The Stilt’ did something that no1 in the motherboard business hasn’t figured out or AMD didn’t implement x87 instructions, for reasons unknown. AMD is not really preferred platform to make Super PI benchmarks with.

The Stilt revealed in a massive post made on HWBOT forums stating that SuperPI uses legacy X87 instruction. Despite not having any real world use, poor reference of real world performance or purpose as newer programs are calculating PI almost 100 times faster, SuperPI is still considered as an industry standard and one of the preferred benchmarks by old school overclockers because it scales CPU, Northbridge, DRAM/ IO and makes tweaks to show improvement in SuperPI is a big challenge.

The Stilt made a utility called ‘Bulldozer Conditioner’ R1.00-B, which can enable x87 Instruction on the AMD processors. Once the fix was applied, Super showed 18-30% improvement in performance.

It should be noted that AMD has disabled X87 instruction set in the first place. It was also pointed out that AMD did not show this in any documentation. It isn’t clear whether or not AMD disabled the feature for some design issue, but the existence of x87 instructions are present in early Zambezi rev batches, Richland and most likely the architecture that would come from now onwards.

The Stilt tested this fix with Richland, Trinity and Vischera. When he tried to verify the fix working with Zambezi however the system crashes followed, because these register changes didn’t respond on Zambezi CPU, therefore the values were nulled.

Question now remains: Why did AMD go through this length to disable x87 instructions that would greatly benefit from Super PI runs?


It was also being found out that AMD have protected the registers with ESI/EDI password. Still, The Stilt did some implementation on Zambezi which allowed >1 second improvement for SuperPI 1M, SuperPI 8M enjoys >10 second and 32M gets >35 second improved.

The entire log can be read over here, and the utility can be downloaded from here.

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