AMD's B3 Stepping Phenom Previewed, TLB Hardware Fix Testedby Anand Lal Shimpi on March 12, 2008 12:00 AM EST
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The first B3 Stepping Phenom
We managed to get our hands on a 2.2GHz engineering sample B3 stepping Phenom:
AMD will begin shipping production B3 Phenoms later this quarter, presumably at higher clock speeds than the 2.2GHz - 2.3GHz launch parts. Our B3 sample was very similar to our B2 chip in that we could get it stable at 2.6GHz but didn't have much luck getting it to run comfortably any faster. We suspect that it'll take a move to 45nm before AMD can really start to push the clock speed on Phenom.
To get an idea of how much of a performance hit the software/BIOS TLB fix incurs we took a small selection of our normal CPU tests and ran with the patch enabled/disabled on a B2 stepping Phenom 9600 (2.3GHz):
|SYSMark 2007||DivX||CineBench R10||3dsmax 9||WinRAR|
|AMD Phenom 9600 (B2 Stepping) - TLB Fix Disabled||117||74.3 fps||7396||7.20||1348 KB/s|
|AMD Phenom 9600 (B2 Stepping) - TLB Fix Enabled||105||72.0 fps||7031||6.47||367 KB/s|
The smallest performance impact was a meager 3.1% reduction, but we suspect that 10%+ would be far more typical. WinRAR is a particularly extreme case where performance dropped by over 70%, which AMD indicated would happen given the heavy memory access nature of file decompression applications.
The new B3 stepping Phenom shouldn't perform any differently to a B2 stepping chip with the TLB fix disabled, but to confirm we ran the most extreme test once more:512 256MB
|AMD Phenom 9600 (B2 Stepping) - TLB Fix Disabled||1348 KB/s|
|AMD Phenom 9600 (B2 Stepping) - TLB Fix Enabled||367 KB/s|
|AMD Phenom B3 @ 2.3GHz||1357 KB/s|
As expected, all is good with B3. The TLB Fix option actually disappeared from the Gigabyte 780G's BIOS upon inserting a B3 chip, it's like the problem never existed.
With the TLB erratum fixed in B3, AMD is one step closer to a competitive Phenom part. Unfortunately Phenom still suffers from low clock speeds and that's something AMD will be working on in the coming months. It will take a combination of higher clock speeds and very competitive pricing to really save Phenom.