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192bit bus, whats this mean?

Paracelsus said:
192 bits refers to the width of the memory bus ie. it can transmit 192 bits at a time from memory to GPU. The number of times it can do this per second is based on the speed of the VRAM ie. 6GHz.

So a smaller bus is not a problem in and of itself as long as the speed of the VRAM is sufficiently high, thus looking at the bus alone isn't really helpful. This is why we're seeing smaller bus sizes these days, VRAM speed is significantly higher so there isn't a need for a super-wide bus.

Case in point.. old school top end card 8800GTX - 384 bit bus linked to 1.8 GHz VRAM, memory bandwidth = 86.4 GB/s.
GTX680 - only 256 bit bus but 6GHz VRAM, memory bandwidth = 192GB/s.
Click to expand...

Yup theres 3 (main) components that have implications for the performance of the VRAM - the bus width (literally how many lanes it has), the bus speed (how many times a second data is transferred over it) and the bus latency (how quickly data gets from one side of the bus to the other).

For the simplest appraisal of VRAM performance you want to be looking at the bus bandwidth usually denoted in GB/s as above, latency can also have some performance implications but its a much more complicated subject.
 
andybird123 said:
http://www.guru3d.com/articles_pages/msi_geforce_gtx_660_twinfrozr_iii_review,24.html

at 4x and 8x AA, the 192bit doesn't seem to hold back 660 SLI
Click to expand...

Depends though - you've got to compare the drop off in performance at the different AA levels to really get a feel for how the bus width affects it.

Tom's did such a comparison and the drop off at 4x AA was harsh on the 192 bit bus and fairly sharp even on the 256 bit cards. Of course the fact you're comparing a lesser GPU against a better one factors into this (660 Ti vs 670) but they also benched a 7870 which roughly matches 660Ti (or the 660Ti is a touch faster) and still the drop off was a lot sharper.

So you can still push decent frames it just means that you're going to be sacrificing settings earlier into your GPUs lifetime to maintain a decent FPS.
 
guys, in all honesty I've got the option to have a 680 for £300, should I take that over a set of 660 in sli for a total of £350.
 
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