
Just to emphasise, I meant no disrespect
Xtasy. I just seem to keep repeating myself so much regarding 4200-128 vs 4200-64. However you make a very fair point in that it seems to you that 4200-64 mostly come with 3.6ns while 4200-128 mostly use 4.0ns.

A big problem seems to be the lack of information retailers and manus have. They tout all of the pretty pointless paper specs and features, even give pics of the cards, but one of the most important things (as we know) is the RAM rating. I hope the samples reviewers receive use the same RAM as the cards consumers buy, it hasn't always been the case. I think it does depend upon where you live, US vs Europe vs Australia show very different pricing, manus and RAM ratings. Many Aussies have even shown me many links to various 4200-128 cards using 3.3ns! Of course it is ALMOST certain to only reach around 600mhz, just like 3.6ns as the TSOP (etc) of the 4200 design limits much higher RAM clocks, but that's another point.

Here's some links and benchmarks I have noted since the 4200 release. I quote the card used and the attained o/c as well as average out all of the given benchmarks of 4200-128 vs 4200-64 at their default clocks.
Tech-Report
4200-64 has only a 1.5% advantage over 4200-128.
O/C 4200-64 to 275/550, reached 300/580 but a little unstable. 4.0ns.
TomsHW
4200-64 (simulated 4200-128 with 4200-64 default clocks of 250/500) has a 6.5% advantage over 4200-128 (250/444) but bear in mind the simulated 4200-64 has 128MB.
O/C 4200-128 to 310/550. 4.0ns.
AnAndTech
O/C Gainward4200-128 to 330/540. 4.0ns.
AnAndTech gfx cards compared
FiringSquad
4200-64 has a 1% advantage.
O/C 4200-64 to 285/600 (3.6ns) which was benchmarked and showed a nice increase except for Commanche4, it was still slower than the 4200-128 even at its default speed of 250/444!
AnAndTech 4200 roundup
Roundup of 4200 cards and esp shows 128MB vs 64MB!
Shows a bunch of 4200 cards and how 64 may become a limitation sooner rather than later.
The FiringSquad example of Commanche4 showing the 4200-64 (o/c 285/600) slower than 4200-128 (def 250/444) could suggest the performance hit when a game requires more than 64MB. But also check out the last link which shows that 64MB cards will begin to lag behind 128MB cards. So personally I think a 4200-128MB with 4.0ns and 300/550 would be preferable to a 4200-64MB with 3.6ns and 300/600, if a 4200-128MB card using 3.6ns doesn't cost much more then that would easily be the best buy. Of course it is important to remember that ALL 4200 cards are GREAT! Even at default clocks they beat both GF3TI500 and full ATI Radeon8500 in pretty much every benchmark, fantastic value for money whatever you buy!