One thing does puzzle me about this card, though. The specs show that it uses a 128-bit memory controller but I thought GDDR5 was 256-bit by default.
No, memory type and memory controllers are separate. GDDR5 memory can use 128 bit, 256 bit, 384 bit, even 64 bit memory controllers.
So if I'm reading this correctly, the GTX 650 is basically Dell's exclusive GT640 GDDR5 with a new name.
I don't know about Dell's exclusive 640, but if the Dell 640 does not use a PCI-E power connector, then no. The GTX 650 uses a power connector.
Yea, I forgot about that. Is the 900mhz version very common? Most people just say the 7750 does not require external power, so they obviously are talking about the slower version. Doesnt it seem strange though that 100 mhz overclock would require that much extra power?
Isnt the regular version rated for only 55w?
The 900 MHz version is fairly available -- it's just impossible to tell unless you specifically look at the clock speed. In a logical worled, the 900 MHz 7750 would be called the 7755, or the 7760. But no, much like the 7950 with boost, AMD made the 900 MHz 7750 the same SKU as the original. And in this case, they didn't even remove the original from the market, since the original still carries the "advantage" of not requiring a power connector.
The way I heard it, 800 MHz was simply as high as AMD could reliably clock it without the power connector. The chip usually could go faster (heck, the full 7770 is made to hit 1 GHz), the lack of power was just holding it back.