Question about # of pipelines in the 1900XT

[ForumMaster]

hi. i just read the AT article about the 1900xt and i was wondering...doesn't the tripleing of the amount of pipelines decrease in performance (intel for example versus AMD)? i mean, it's nice and all but is it really worth it? ty for helping me understand this...

 

[ribbon13]

Much different kinds of pipelines. CPU pipeline determines how it execute instructions and how well it does branch predictions, whereas the pipelines on GPUs (pixel shaders and vertex shaders) are like multiple individual processors doing a specific function. So more of them allow you to do more.

 

[ForumMaster]

ok then. thnx. wow! then the 1900xt must be on hell of a strong card! it has 48 pipelines!

 

[TSS]

still wrong im afraid.

it doesnt have 48 traditional pipelines, it has 16 traditional ones, but each one contains 3 pixel shader units. so basicly, it only has 16 pipes but each pipe can handle up to 3 times more shaders then the 1800xt.

edit: think of it as a boat. the 1800xt is a normal boat. but the 1900xt is the same hull, same engine, but 3 propellors. it'll move more water, thus beeing a bit faster, but the engine and the hull (water resistance) still limit the boat. thus, its not as fast as having 3 enignes, a more efficient hull and 3 props, 1 for each engine.

yeah i know, weird, but the best i could come up with.

 

[BrownTown]

wow, where to start...

First, the X1900XT doesnt have 48 pipelines, it has 16. The number 48 is the number of pixel shaders it has. Each of the 16 pipes can do 3 shader operations per clock, so it actually has less pipelines then the 7800GTX. Secondly, you don't really ever refer to the number of pipes in a CPU. What you are refering to is the number of pipeline stages. This means the number of clockcylces that it takes to execute an instruction. So in other words it takes 31 clockcycles for a P4 to execute an instruction, while it takes a A64 only 12.