Bundles said:
GDDR3 was available for AGES before it became widespread though. Who remember the 9800 non pro with 256mb GDDR3? while the 9800pro still had 128mb GDDR2.
not quite right, the 9700/9800's started with ddr only, the 9800 xt came out with 256mb ddr mem, and a few 9800 256 ddr2 came out late for no apparent reason
, i guess they were just playing around with some ddr2, seeing if it was any good. i seem to remember them being a nightmare to overclock with very hot running ddr2 chips.
x800's had pretty much only ddr3, with some of the 12 pipe 128mb versions with low clocked ddr2(possibly even some ddr, not sure).
gddr3 has scaled pretty damned well, x800's had, i think started at what the 800Mhz kinda speed and is now up to 1.8Ghz. gddr3 has been here since, well, a little over 2 years now since the x800 came out.
as for mem designed for graphics cards as opposed to desktops, there isn't a "huge" difference, its still double data rate memory you can't get away from that. but the reason they can scale so high compared to system memory is the latency's they use, they are very very high latency which would be fairly useless for desktop performance. but for higher resolutions, and aa/af settings the way the gpu's add aa/af is fairly simple, the only issue is pushing the data through as all the picture needs to be checked to see if it can have aa/af applied to it. to do this you need a massive massive bandwidth where as latency isn't so much an issue. this is why you run a card at say 1600x1200 with max aa/af and only overclock the memory and see huge gains in performance, where as without aa/af the extra mem bandwidth is fairly underutilised and doesn't show a big performance boost at all. do'h ati tool can let you see mem timings, but whatever version i have isn't letting me see them
http://www.csl.cornell.edu/courses/ece699/GDDR3.ppt
slide 21/27 in that, cas latency runs from 7 to 11 inbetween 500/800Mhz. a few pages in that show some useful info,
samsung seems to spec from cas 5-9 from 500 to 700 mhz, so possibly a little tighter on timings, but up at 900Mhz you get on 7900's it will probo be 10-12. i guess to a point ddr2 is now hitting 500mhz and can be done at the cas 4/5 settings, but tighter on everything else too, uses more power and has taken 2 years to catch up to those kind of speeds.
