(Copied-n-pasted over from
http://alienbabeltech.com/abt/viewtopic.php?f=6&t=21797&start=290#p72391)
My quick opinion of the biggest single-GPU "leaps" in in the last 10 years:
1) Geforce 7900GTX -->
8800GTX (2.3x faster, also 2x faster than X1950XTX - all on the same node within 1 year!!!) Plus DX10!
--- the caveat being that it was monstrous in silicon size, yet it only ate about 10-20W more than the X1950XTX which was half as fast, while being even quieter!! Compared against the fastest single GPU of the previous 110nm generation, the 7800GTX-512, it was over 2.5x faster!!
2) Radeon 8500 -->
9700 Pro (2.3x faster, also around 70% faster than the same-node flagship Geforce4 4600 Ti) Plus DX9!
--- there was a lot more silicon, maybe 30-50% more power consumption and heat output, though, but it was not an issue though! Compared against the fastest single GPU of the previous 0.18 micron generation, the Geforce 2 Ultra, it was over 3x faster!!
3a) Geforce 5950 Ultra -->
6800 Ultra (80% faster - same node - also over 70% faster than the previous node flagship 9800XT)
--- although not exactly as fast overall as the single-slot X800XT launched at around the same time, it brought DX9.0c and also brought SLI back!!!
3b) Radeon 9800XT -->
X800XT (80% faster - at 0.13 micron vs 0.15 micron - also almost 90% faster than the same-node flagship Geforce FX 5950 Ultra)
--- similar size, power envelope, and noise output - one of the last cards to do
all of this at once from flagship to flagship, while virtually doubling the performance!
4) Geforce 8800 Ultra -->
GTX 280 (61% faster - at 65nm vs 90nm - also over 70% faster than the 65nm 9800GTX)
--- the biggest GPU ever, yet not too shabby gains in power draw or noise output - the 8800 Ultra really pushed the power envelope anyways
5) Radeon HD 4890 -->
HD 5870 (52% faster - at 40nm vs 55nm - also over 30% faster than GTX 285)
--- it would not have made the list if it were not for the introduction of DX11 that it brought, while actually remaining within the similar size and power envelope as the 4890 (Bonus, HD 5970 based on the same chip did what AMD could not do with HD 3870X2 - dominate with grace and ease, unlike when HD 4870X2 had to do it at such a tradeoff of considerable noise and power draw.... if not for DX11, 7800GTX-512 would've taken this spot)
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As for the greatest bang-4-buck ever (IMHO):
1) GTX 460 1GB which could have been grabbed with special discounts as low as $120. Faster than the flagship GPU from the previous generation (GTX 285) that cost $500. Imagine something faster than GTX 580 (as fast as GTX 660 Ti or HD 7950) today for $119 after rebate?
2) HD 4890 which was deep-discounted to around $130 right after HD 5870 was launched at a not-so-bad $399. It was already over 50% faster than the previous-gen's flagship 8800 Ultra which went for $700+ a little over a year earlier.