| Zappykins said: While I will confirm Sony has the better GPU, they messed up again. GDDR5 RAM is great for graphics, it should make nice pretty pictures – But unfortunately, it comes at a cost - huge latency. I'm not talking about twice as bad, or even 5 times, but 7-10 times as much latency as DDR3 memory. It will cripple all the other advantages they put in it – like the wider bus width, speed, etc. It’s really a shame. It will effect everything thing that isn’t just a picture (AI, Game play, etc.) |
No. GDDR5 does not have massive latency hit compared to DDR3, please stop parroting misinformation.
Go look up the datasheets of the actual chips and you will soon realise latency in RAM has always stayed at about 10ns, infact it's been around that level since DDR1.
However, since datarates on Ram have been increasing over the years so has the latency in clock cycles, but the absolute latency has been relatively static.
Grab some DDR3 1600mhz memory, that's 800mhz IO, which has a typical CAS latency of 8, that means it has a latency of 10ns.
Grab some DDR2 800mhz memory, that's 400mhz IO, which has a typical CAS latency of 4, this is also 10ns.
Now with GDDR5 the data rates are 4x faster than the IO clock instead of 2x, I.E. 5ghz GDDR5 is 1.25ghz x4 and would have a CAS Latency of 15.
15/(1.25 GHz) = 12 ns
So the latency of GDDR5 is only 20% higher than DDR3.
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