Monday, March 9th 2009

Phenom II X4 800 Series Can Address Full 6 MB L3 Cache

While AMD played smart in diverting all its engineering resources in designing only one core: the Deneb / Shanghai, and then carving out umpteen SKUs out of them based on disabling cores, and/or setting L3 cache amounts, its implementation seems to be shoddy, to the least. Weeks ago, a Korean enthusiast found an easy way to unlock the factory-disabled fourth core on some Phenom II X3 (Heka) processors. A fresh report suggests that it is possible to enable the complete L3 cache on the Phenom II X4 800 series processors.

The series is AMD's line of Deneb-based 45 nm quad-core processors with 2 MB of L3 cache disabled, leaving 4 MB that can be addressed by the processor. An enthusiast found the Phenom II X4 810 processor to be spontaneously able to address 6 MB of L3 cache, when used on an ASRock AOD790GX /128M motherboard. The most likely cause of this could be "poorly-coded" motherboard BIOS that is able to see the Deneb core "as is". The motherboard was using BIOS version 1.40, that adds Phenom II support. The additional cache was found to have a positive impact on system performance. Beyond that, the enthusiast did not provide an explanation. After clearing the CMOS of the motherboard, it was able to correctly detect the processor with its intended specifications.

Source: XTReview
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15 Comments on Phenom II X4 800 Series Can Address Full 6 MB L3 Cache

#1
btarunr
Editor & Senior Moderator
Many Thanks to cdawall for sending this in.
Posted on Reply
#2
Imsochobo
seems like you can do alot with theese PHII's.

Its just like the X800 pro VIVO -> XT and all the other gfx's that required minor mods.
Posted on Reply
#3
ShadowFold
When I saw this on the frontpage I facepalmed
Damn AMD, doing anything for sales eh lol
Posted on Reply
#4
r9
Getting free performance is fun.
And yet again unlocking is done on crappy brand board :D.
Posted on Reply
#5
PVTCaboose1337
Graphical Hacker
Free performance = win. Amd gets more sales, we get more speed.
Posted on Reply
#6
BazookaJoe
It was my understanding that the X3 chips where chips that had failed X4 quality control on 1 core - and rather than throw them away they are sold as X3's

This would mean that enabling core no. 4 would be enabling a core that had already been branded reject by the factory.

Is this wise? - I'd rather just buy a 4 core CPU - that has PASSED quality control - is there REALLY such a price difference?
Posted on Reply
#7
soryuuha
by: BazookaJoe
It was my understanding that the X3 chips where chips that had failed X4 quality control on 1 core - and rather than throw them away they are sold as X3's

This would mean that enabling core no. 4 would be enabling a core that had already been branded reject by the factory.

Is this wise? - I'd rather just buy a 4 core CPU - that has PASSED quality control - is there REALLY such a price difference?
$72 usd?
Posted on Reply
#8
BazookaJoe
OK, I admit that's worse than I thought it would be. :

But personally, I'd still rather pay the extra and not have to worry about stability - At the end of the day you are still unlocking a reject core.

I suppose its really down to where between cost & stability your requirements lie.
Posted on Reply
#9
Kei
I imagine the people that are looking at this most are people who are looking for benchmark runs not people looking for outright stability. Same for the 810 L3 cache thing, it's a cool trick but we all know they disabled it for a reason other than just to make X3's and 4Mb L3 cache levels.

Also, once the bios's for these boards get updated this problem will go away away as these chips are all still on their first bios releases so they're far from optimized just yet. I'm sure a lot of people out there soiled their pants when they found these things though haha.

I however wouldn't try to do either of these on a daily basis because of the risk for instability that is bound to happen at some point.

Kei
Posted on Reply
#10
newtekie1
Semi-Retired Folder
Just because it is disabled, that doesn't mean it is unstable. Some might be perfectly good, but were still disabled just to fill the demand of lower end markets.
Posted on Reply
#11
WarEagleAU
Bird of Prey
Seems like a nice little hidden gem to me. too bad they are gonna correct this minor tweak. Id like to get me an 800 series with 6mb of cache just to see how well it performs compared to the 4mb. Crappy Asrock board, someone try it on the MSI DK790GX uber board.
Posted on Reply
#13
showstopper41
AMD's all new Phenom II's are tricky. If it is possible at all 790GX mainboards, that is a new option against risky phenom II x3 720's 4th core.
Posted on Reply
#14
eidairaman1
i wouldnt be surprised if Modders start taking the later bios code and unlocking it so it detects the processors differently.
Posted on Reply
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