Xen said:
You forget what kind of RAM is it. XDR as far as I rmemeber. And compared to good ol' DDR or whatever the 360 has, it's just faster. It's not only numbers, my friend. |
I think it should be noted that the GDDR-3 interface is 1.4 GHz *effective* clock in the same way that XDR is 3.2 GHz *effective* clock. GDDR-3 transfers 4 bits per clock relative to the DRAM, by using a 4-bit fetch width and a DDR (2bits per clock) bus that is twice as fast as the DRAM clock speed. Meaning a 1.4 GTransfers/sec rate = 700 MHz bus clock (DDR) = 350 MHz DRAM clock. 1.4 GTransfers per second * 128 bits wide bus = 22.4 GB/sec.
In XDR's case, it transfers 8 bits per cycle relative to the DRAM. This is done in a similar way, except the otherwise DDR bus is 4x as fast as the DRAM clock instead of just twice as fast (and of course, the fetch width is 1 byte). So 3.2 GTransfers per second = 1.6 GHz bus clock = 400 MHz DRAM clock. 3.2 GTransfers/sec * 64 bits wide bus = 25.6 GB/sec.