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Aielyn on 29 January 2013
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ethomaz said:
The Wii U GPU die size is 156mm^2 with eDRAM... 32MB eDRAM... without it the part of die for the GPU alone is below 104mm^2.

For over 500 GLOPS using the HD 7000 arch you need at least 480 SPs running at 550Mhz (I'm using the Wii U GPU clock)... 480 SPs in this arch have a die size of ~115mm^2... that is bigger than 104mm^2 of the Wii U GPU.

The HD 4770 (704GFLOS @ 55Mhz) have a die size of 137mm^2... bigger than the 104mm^2 too.

There is no AMD tech to put over 520 GFLOPS in 104mm^2 running at 550Mhz... or you have a die size bigger or you run the GPU at higher clock to archive over 500 GFLOPS.

You know witch AMD GPU fits exactaly in the 104mm^2? Radeon HD 5670 (Redwood)... 400 SPs @ 550Mhz = 440 GFLOPS.

Remeber... the 32MB eDRAM uses at least 55mm^2 of the 156mm^2.

I'm sorry, but at this point, I won't accept what you're saying until you provide sources backing up your claims. And from what I can find, the argument of "the GPU alone is 104 mm^2" comes from the assumption that it's based on Redwood, not vice versa.

Also, your numbers don't match up. You claim that the eDRAM must use at least 55 mm^2... but that leaves just 101 mm^2, less than the 104 mm^2 that you claimed the Wii U GPU must be using.

Meanwhile, there's the AMD Radeon HD 7670M, which has a die size of 104 mm^2, a 40 nm process, a clock speed of 600 MHz (Redwood has a clockspeed of 775 MHz), and pushes 576 GFLOPS - at 550 MHz, that's 528 GFLOPS, which again contradicts your claim, which was that there is no AMD tech that can put over 520 GFLOPS in 104 mm^2 running at 550 MHz. And at 600 MHz, it uses only 25 W, if I'm reading this correctly, which means that it'll use maybe 20-22 W at 550 MHz... which is right around where it should be, if I understand correctly - my understanding is that the system uses 40 W when active.

And if it's based on the 7690M XT, then it should work out even lower in power usage, since it still has 25 W with a higher clock speed (and therefore should have an even lower power usage when underclocked). Or perhaps it's based on the 7590M, which performs pretty much in line with the 7670, except only requiring 18 W.

Meanwhile, the only reference I could see to the association of 32 MB of eDRAM to 55 mm^2 goes back to 2004/2005, except one instance on Beyond3D, where one guy speculated that, since IBM get 61.4 mm^2 at their 45nm process for 32 MB of eDRAM, then at 40nm, it should be about 55 mm^2. The problem is, this guy sucks at mathematics and scaling. 61.4*40/45 = 54.5, which is likely where he got 55 from. But area works with the square of the scale, so it's actually 61.4*40^2/45^2 = 48.5.