I have an obsolete NVIDIA GTS250 1 G and it is specified as having a bandwidth of 256 bit. When I study currently sold videocard I notice that it's only the more expensive card that has such high bandwidth as 256 bit. Many have only 128 bit but their clock frequencies are higher. Does anyone know why it is like this ? What conclusion can be made when comparing an old card with 256 bit BW and a new for example GTX650 with 128 bit BW ?

Jfri

Its all to with RAM type and speed and this a good article to read: http://www.tomshardw...what-difference and http://voices.yahoo....ce-3289088.html. Using the data from http://www.gpureview...1=606&card2=667 The memory bandwith of the GTX260 is 70.4GB/sec whereas fo the GTX 680 its 192.625 GB/sec so although they both be 256 b-it the faster RAM in the 680 makes th difference and a 128-bit card with faster RAM will have a greater memory bandwidth than a 256-bit card with slower VRAM.

The 128bit and 256bit are bus widths not bandwidths. There's a big difference. You also have the speed of the memory. To get the important bandwidth you multiply bus width and speed. That tells how much data that can be moved over the same time. GDDR5 is capable of a lot higher speeds than GDDR3 and slower memory types.

 

A wider bus requires a lot of space on the chip so its expensive to build. So when the price of GDDR5 came down it made more sense for the video card manufacturers to use a narrower bus with a lot faster memory, with the end result: higher performance cheaper.