Does Bulldozer die shot reveal triple-core 'modules'?

— 2:21 PM on September 2, 2010

GlobalFoundries wasn't the only firm with interesting news at the Global Technology Conference. AMD was also present, and for the first time, it publicly displayed a die shot of a Bulldozer-based processor: Orochi, the chipmaker's 2011 flagship processor. PC Perspective's Ryan Shrout was on the scene and managed to snag a picture.

Shrout's photo shows a 32-nm die with what appear to be four Bulldozer modules. As we wrote last week in our overview of AMD's new architecture, each Bulldozer module has two integer cores and a shared floating-point unit. Operating systems will detect two threads per module, and AMD says each module will be about 80% as fast as two full cores with the same capability. One would therefore be inclined to think the Orochi die has four modules and eight threads.

Except it's not so simple. We loaded Shrout's die shot photo into Photoshop and compensated for the perspective using the application's "Distort" tool.

Nothing jumping out at you? How about if we crop away that pesky L3 cache (or what looks like it), rotate the bottom half 180 degrees, and try to line up the logic:

Clearly, the Bulldozer modules at the top have more logic and less cache (presumably of the L2 variety) than the modules at the bottom.

I got a little more adventurous, taking the logic part of the bottom-left module and duplicating the section between the green lines in the image below:


Line up the Photoshopped logic portion with the genuine one at the top left, and things appear to match up pretty well. Note those three bright white blocks at the top, the repeating pattern just below them, and the lighter blocks below that.

If all of this tomfoolery tells us anything, it's that there may be more to Orochi and Bulldozer than meets the eye. This CPU appears to have two regular Bulldozer modules and two enhanced ones. The question is how exactly those modules are enhanced. Did AMD add extra integer logic, extra floating-point logic, or both? Could these modules serve up three threads to the operating system, thereby making Orochi a 10-thread CPU?

Update: We asked AMD about this picture and its possible meaning, and we got a cryptic but possibly helpful answer. It was pointed out to us that PC Perspective did not publish a picture of the Orochi die, but a snapshot of an image shown at the event. We understand parts of that image were "obscured" for "competitive reasons," whatever that means.

Did AMD doctor the die shot, altering the image to show logic where it may not exist in reality? We don't know, but apparently there was something AMD didn't want Intel to see. And the mystery deepens.

Tip: You can use the A/Z keys to walk threads.
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