(I edited this due to leaving out something important and I decided to fix the numbers I made a shortcut on)
I checked the specs on the graphics card and there was some conflicting info but here goes.
The RAM is between 400MHz and 500MHz DDR2 depending on what I read. The PRO version is 600MHz. <edit> The pro version is actually 800MHz</edit>
The current specs on the manufacturer website say 500MHz as is my card (according to ATi Tools) but they may have made some with 400 or 450 that went out to reviewers. (I think the problem is the author of the articles) The memory interface is 128 bit.
So.... memory bandwidth should be one of these:
400 * 2 * 128 / 8 / 1000 = 12.8GB/s
450 * 2 * 128 / 8 / 1000 = 14.4 GB/s
500 * 2 * 128 / 8 / 1000 = 16 GB/s
600 * 2 * 128 / 8 / 1000 = 19.2 GB/s
800 * 2 * 128 / 8 / 1000 = 25.6 GB/s
For those scratching their heads... the first number is the RAM clock in MHz, the 2 is for the DDR (Double Data Rate) which transfers data twice per clock cycle, the 128 is the memory width on the card in bits, the 8 is the number of bits in a byte and the 1000 is the conversion from Mega to Giga.
Even the lowest should be enough for HDTV.
My memory is supposedly overclocked to 513 for 16.416GB/s.
That makes the problem I'm having software related. Scratch one more possibility!
Now... those numbers don't include real world things like memory refresh and other things that cut performance but there's enough extra bandwidth there to make up for it.
If I didn't mess up the formula (entirely possible) then any card with DDR 400 or faster memory should be sufficient.
I have no idea where someone got just over 8 GB/s unless they forgot that DDR doubles the transfer rate... in which case I wouldn't trust them much as a source of information. That or they calculated with a 64 bit buss... which there seems to be some confusion about. The X1300 doesn't have the ring buss controller upper models have that people are saying cuts the true buss width in half. |