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finding bandwidth?

M

mattsmall

Gawd
Joined
May 4, 2003
Messages
831
on the memery how do you find the bandwidth per second? is there some programe?

ex:9800xt has 23.3GB per second of bandwidth over the card's 256-bit memory bus
 
the speed of the memory (DDR) times 32 if its a 256bit bus or 16 if its a 128bit bus

for example a 9800XT's memory speed is 730MHz so times 32 = 23.3GB/sec
 
so a 9500pro at 425core and 630mem would have 10.080 gb sec? isnt that what it has stock
 
...unless you want to measure GB/s as 1024^3 bytes/s= 1 GB/s. ;) I wouldn't get too picky with bandwidth as I do with memory/storage sizes. I personally like the larger number for bandwidth figures.

But say you had a 128MB video card and you consider reading the whole memory space 8 times in 1 second as 1GB/s of bandwidth (8 x 128MB = 1GB). So in your test, do you stop when you reach 1,000,000,000 bytes read and leave the other 73,741,824 bytes in the GB unread (around 7% remaining, a little less than 1/2 of the last of 8 128MB reads)? So 10.08 billion bytes/s of bandwidth really equals only 9.39GB/s.

Or if you've been brainwashed by hard drive manufacturers that 1GB = 1 billion bytes as their disclaimers state with little *'s, I guess there's no point arguing. If that were true, why do they need an explicit disclaimer?

Please, no one start with GiB... no one uses that.
 
Originally posted by pxc
...unless you want to measure GB/s as 1024^3 bytes/s= 1 GB/s. ;) I wouldn't get too picky with bandwidth as I do with memory/storage sizes. I personally like the larger number for bandwidth figures.

But say you had a 128MB video card and you consider reading the whole memory space 8 times in 1 second as 1GB/s of bandwidth (8 x 128MB = 1GB). So in your test, do you stop when you reach 1,000,000,000 bytes read and leave the other 73,741,824 bytes in the GB unread (around 7% remaining, a little less than 1/2 of the last of 8 128MB reads)? So 10.08 billion bytes/s of bandwidth really equals only 9.39GB/s.

Or if you've been brainwashed by hard drive manufacturers that 1GB = 1 billion bytes as their disclaimers state with little *'s, I guess there's no point arguing. If that were true, why do they need an explicit disclaimer?

Please, no one start with GiB... no one uses that.
Click to expand...

my brain just exploded
 
Originally posted by Brent
the speed of the memory (DDR) times 32 if its a 256bit bus or 16 if its a 128bit bus

for example a 9800XT's memory speed is 730MHz so times 32 = 23.3GB/sec
Click to expand...

You're correct in finding the theoretical bandiwidth, but your leaving out a step as to how this is found. You're doing 32 for 256bit, and 16 for 128bit, this is correct in a way, but the actual way of finding bandwidth is this: Speed multiplied by the bus width devided by 8 (it's devided by 8 because there's 8 bits in one byte, and typically bandwidth is in bytes).

So bandwidth of 9800xt: 730mhz X 256bits/8 = 23.3GB/s. Same answer as Brent, just without the missing step.
 
Originally posted by EarthwormJim
You're correct in finding the theoretical bandiwidth, but your leaving out a step as to how this is found. You're doing 32 for 256bit, and 16 for 128bit, this is correct in a way, but the actual way of finding bandwidth is this: Speed multiplied by the bus width devided by 8 (it's devided by 8 because there's 8 bits in one byte, and typically bandwidth is in bytes).

So bandwidth of 9800xt: 730mhz X 256bits/8 = 23.3GB/s. Same answer as Brent, just without the missing step.
Click to expand...

my way is easier to remember :D lol
 
Originally posted by mattsmall
ha my 9500pro has more bandwidth then a stock 9700pro:D woot
Click to expand...
9500pro has a 128bit mem bus, as opposed to 9700's 256.
 
Originally posted by mattsmall
ha my 9500pro has more bandwidth then a stock 9700pro:D woot
Click to expand...

I think you're confused and think you flashed your 9500pro to a 9700, which is not possible. It was only the L shaped 9500 NON PROS that could be flashed. And all the flashing did was enable the 4 disabled pixel pipelines. So with your card there is nothing to flash it into.

Your card runs on a 128bit bus vs. the 256bit bus for 9700's and the L shaped 9500non pros. So sorry bud, you don't have more theoretical bandwidth than a stock 9700pro
 
Sorry :( ... You'll never get it on a 128-bit bus with the ram on that 9500 Pro...even if it was like 2.5ns

You'd need a memory clock of 625MHz (1250MHz) to achieve 20GB/sec of memory bandwidth on a 128-bit bus.

Right now you have ~11GB/sec mem bandwidth. Thats pretty good for and on a 128-bit card.
 
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