Also from Toms Hardware:
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Matrox describes Parhelia as the first 512-bit GPU (Graphics Processing Unit) in the world, which accounts for the "512" that appears in the full name for the chip. It comes with a 256-bit wide memory bus, which is able to transfer 512 bits of data per clock, because of its double data rate capability. This may just be a number to you, but in practice, this is some rather amazing stuff. It increases the pin count of the chip by an incredible number and it makes the PCB of the graphics card a lot more complex too. There's a good reason why neither NVIDIA, nor ATi have tried that yet. Right now, Parhelia demo boards have no less than 8 layers! At 300 MHz memory clock (600 MHz DDR), Parhelia has a whopping memory bandwidth of 20 GB per second. By comparison, NVIDIA's top product, the GeForce 4 Ti4600, just reaches 10.4 GB/s. However, with its Lightspeed Memory Architecture II, NVIDIA has provided its graphics cards with a very effective Crossbar Memory Controller, lossless Z-compression and further optimizations.
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So much for 'Look at the specs, it's a hoax'! These are the specs, and it's no hoax:-)
For more see:
http://www.tomshardware.com/graphic/02q2/020514/index.html :-D