My Win XP 32bit with 4GB RAM and a 768MB 8800GTX showed ~ 3.2GB available physical memory.
Aria have an
XFX 4650 which claims to be 128bit on super special at the minute: £35.24. Pretty bargainous if the specs are right (although it *is* an XFX, of course...
).
Otherwise, 128bit 4650s seem to be ~ £55 (except
this one from Novatech @ £50, but it's got a double slot cooler...) - frankly you might as well go for a 4670 at that point:
Passively cooled Sapphire version £59 @ ebuyer
Actively cooled ASUS version £56 @ scan
Oh, and a p.s. to the pedants - I did indeed mean smaller capacity, and was very specifically referring to the ASUS
low profile 4650: the 512MB version is identical to the 1GB version except with half the memory chips pulled off! Halfing the bandwidth as well as the frame buffer seems a little extreme to me: it's barely a 4650 once you do that. ATI should ban companies from selling graphics cards that far out of spec: should've been called a 4630 or something (and don't get me started on XFX's DDR2 4670
)...