• why do ati cards have such enormous high memory speeds?
    23 replies, posted
well, why?
because they're good cards?
Multiplication due to GDDR3/GDDR5 properties. Divide advertised GDDR3 speeds by two and advertised GDDR5 speeds by four. For example, a 5870's VRAM is really only running at 1.2 GHz, not 4.8. They just say "4800 MHz effective" or something like that when it's really only running at 1200 MHz, but has a transfer rate of 4800 Mb/s because GDDR5 is extremely efficient. ATI uses GDDR5 on its newer cards while nVidia is stuck on GDDR3, which is only half as efficient, and would only transfer 2400 Mb/s at 1200 MHz. But due to the high efficiency of GDDR5, ATI can play up the numbers and make their VRAM seem like it's much faster than it really is. In the long haul, however, none of this really matters... just look at benchmarks and prices, not spec sheets.
so ATI has faster memory on their cards, right?
[QUOTE=mark112666;18321518]so ATI has faster memory on their cards, right?[/QUOTE] sure, but it's not like it makes a huge difference... if you're comparing cards, look at benchmarks, not whitepaper specs for example, a GTX 285 and a 5850 perform similarly, but the GTX 285 has GDDR3 while the 5850 has GDDR5
what really holds them back is the bit rate.
[QUOTE=sbradford26;18323104]what really holds them back is the bit rate.[/QUOTE] What the hell are you talking about? What really holds them back is the GPU. A 4870 and a 5870 both use GDDR5, but a 5870 is twice as fast even though the VRAM is only 33% faster.
[QUOTE=and;18323247]What the hell are you talking about? What really holds them back is the GPU. A 4870 and a 5870 both use GDDR5, but a 5870 is twice as fast even though the VRAM is only 33% faster.[/QUOTE] I know the only reason nvidias ddr3 stays any bit close is because of its high bit rate.
[QUOTE=sbradford26;18323528]I know the only reason nvidias ddr3 stays any bit close is because of its high bit rate.[/QUOTE] show me the source for this bitrate information (and then never visit the site again)
[QUOTE=and;18324116]show me the source for this bitrate information (and then never visit the site again)[/QUOTE] Ahhhh, I must explain this to a very simple minded person now, bit rate on memory really matters cause memory with a 64 bit memory speed is twice as fast as memory with a 32 bit rate. If they run at the same speed.
[QUOTE=sbradford26;18324259]Ahhhh, I must explain this to a very simple minded person now, bit rate on memory really matters cause memory with a 64 bit memory speed is twice as fast as memory with a 32 bit rate. If they run at the same speed.[/QUOTE] You best be trollin' Seriously if not then never post in the hardware and software forum again as you will have puked and stamped on your own reputation.
[QUOTE=Jallen;18324304]You best be trollin' Seriously if not then never post in the hardware and software forum again as you will have puked and stamped on your own reputation.[/QUOTE] You guys have no idea what memory bit rate does do you. I has a massive impact on the performance of graphics cards.
[QUOTE=sbradford26;18324321]You guys have no idea what memory bit rate does do you. I has a massive impact on the performance of graphics cards.[/QUOTE] Your vague response obviously was meant for us to respond with irritation and a large explanation about how you are retarded. Guys, don't feed this troll, he's not entertaining.
[QUOTE=Jallen;18324361]Your vague response obviously was meant for us to respond with irritation and a large explanation about how you are retarded. Guys, don't feed this troll, he's not entertaining.[/QUOTE] Really you have no idea how a computer works. Lets make an example, lets say a graphics card with a 128 memory bandwidth can transfer 5 units per packet that means if there are no outside factors the a 256 bit memory bandwidth would be able to transfer 10 units per packet. [editline]07:07PM[/editline] Also kinda old but hard to find a good article on this topic here you go [url]http://www.playtool.com/pages/vramwidth/width.html[/url]
[QUOTE=sbradford26;18324466]Really you have no idea how a computer works. Lets make an example, lets say a graphics card with a 128 memory bandwidth can transfer 5 units per packet that means if there are no outside factors the a 256 bit memory bandwidth would be able to transfer 10 units per packet. [editline]07:07PM[/editline] Also kinda old but hard to find a good article on this topic here you go [url]http://www.playtool.com/pages/vramwidth/width.html[/url][/QUOTE] [QUOTE=sbradford26;18323104]what really holds them back is the bit rate.[/QUOTE] This is the comment which is stupid. Do you honestly think that ATI couldn't slap a 512 bit memory bus on their cards if they wanted to? The whole point is that it doesn't do crap, they give the card a bus size which is appropriate considering other factors which is why I thought you were a troll. The architecture would have to be considered to truely make ANY assumptions about bus size. The GPU itself has to actually be able to utilize the individual data transfer streams to even take advantage of the huge bus size. There is no point in giving an 8 bit intel CPU a 64 bit address bus and the same principles apply here, it depends entirely on architecure of other components. To quote you, "Really you have no idea how a computer works."
[QUOTE=Jallen;18324742]This is the comment which is stupid. Do you honestly think that ATI couldn't slap a 512 bit memory bus on their cards if they wanted to? The whole point is that it doesn't do crap, they give the card a bus size which is appropriate considering other factors which is why I thought you were a troll. The architecture would have to be considered to truely make ANY assumptions about bus size. The GPU itself has to actually be able to utilize the individual data transfer streams to even take advantage of the huge bus size. There is no point in giving an 8 bit intel CPU a 64 bit address bus and the same principles apply here, it depends entirely on architecure of other components. To quote you, "Really you have no idea how a computer works."[/QUOTE] I know that if they could they would but it still doesn't mean it wouldn't help to have a high bit speed.
[QUOTE=sbradford26;18324781]I know that if they could they would but it still doesn't mean it wouldn't help to have a high bit speed.[/QUOTE] You are just WRONG. They can, they didn't because it would increase the price of the cards for little to no preformance.
[QUOTE=sbradford26;18324781]I know that if they could they would but it still doesn't mean it wouldn't help to have a high bit speed.[/QUOTE] ATI relies on a balanced price/performance ratio to ship it's cards, and an increased bus size wouldn't make enough difference to warrant the extra cost.
[QUOTE=sbradford26;18324466]Really you have no idea how a computer works. Lets make an example, lets say a graphics card with a 128 memory bandwidth can transfer 5 units per packet that means if there are no outside factors the a 256 bit memory bandwidth would be able to transfer 10 units per packet. [editline]07:07PM[/editline] Also kinda old but hard to find a good article on this topic here you go [url]http://www.playtool.com/pages/vramwidth/width.html[/url][/QUOTE] ATI would've used 512 bit if it really made a difference. But they didn't, so it's obviously not worth it. I'm sure ATI did extensive experimentation with these cards. But just going around theorizing about some higher numbers doesn't suddenly make you an expert... if it were worth it, ATI would've done it.
[QUOTE=sbradford26;18324466]Really you have no idea how a computer works. Lets make an example, lets say a graphics card with a 128 memory bandwidth can transfer 5 units per packet that means if there are no outside factors the a 256 bit memory bandwidth would be able to transfer 10 units per packet. [editline]07:07PM[/editline] Also kinda old but hard to find a good article on this topic here you go [url]http://www.playtool.com/pages/vramwidth/width.html[/url][/QUOTE] I think I'm starting to like this guy.
Oh god this thread made me facepalm. sbradford26 is (partially) right, but it's [b][u]not called bitrate for fuck's sake[/u][/b]. Bitrate is number of bits transferred/time, usually used for measuring the compression of video/audio. What you're talking about is memory bus width, which tells you how much bits are transferred through the bus with each clock cycle. 256bit bus transfers 256bits/cycle, 512bit bus transfers 512bit/cycle, etc. Now memory clockspeed and bus width alone doesn't tell much, the important thing here is [b]memory bandwidth[/b] which tells you how much data is transferred in a certain amount of time. memory bandwidth=bus width*memory frequency So, let's say you have GDDR3 memory running at 2GHz on a 512bit (=64byte) bus: 2.000.000.000cycles/second * 64bytes/cycle=128GB/s you could also use 4GHz GDDR5 memory on a 256bit (=32byte)bus to get the same bandwidth: 4.000.000.000cycles/s * 32B/cycle=128GB/s Now why doesn't ATI use more than 256bit buses? The main reason is that it makes the graphics card a lot more expensive to produce. You need more memory chips and more complex PCB for wider buses. Sure GDDR5 is more expensive than GDDR3, but in comparison to using higher bus widths it's still relatively cheap. GDDR5 can probably reach frequencies of around 5GHz, with a 256bit bus it means 160GB/s, which is plenty of bandwidth. Unless you really need more than that, using wider buses isn't necessary.
Because it is not held together with 1.7 wooden screws, and they don't re-brand their stuff, well I do consider the 5770 and 5750 a rebrand as it is pretty much the 4850 and 4870 but with standard GDDR5 and higher clocks
[QUOTE=pebkac;18334533]Oh god this thread made me facepalm. sbradford26 is (partially) right, but it's [b][u]not called bitrate for fuck's sake[/u][/b]. Bitrate is number of bits transferred/time, usually used for measuring the compression of video/audio. What you're talking about is memory bus width, which tells you how much bits are transferred through the bus with each clock cycle. 256bit bus transfers 256bits/cycle, 512bit bus transfers 512bit/cycle, etc. Now memory clockspeed and bus width alone doesn't tell much, the important thing here is [b]memory bandwidth[/b] which tells you how much data is transferred in a certain amount of time. memory bandwidth=bus width*memory frequency So, let's say you have GDDR3 memory running at 2GHz on a 512bit (=64byte) bus: 2.000.000.000cycles/second * 64bytes/cycle=128GB/s you could also use 4GHz GDDR5 memory on a 256bit (=32byte)bus to get the same bandwidth: 4.000.000.000cycles/s * 32B/cycle=128GB/s Now why doesn't ATI use more than 256bit buses? The main reason is that it makes the graphics card a lot more expensive to produce. You need more memory chips and more complex PCB for wider buses. Sure GDDR5 is more expensive than GDDR3, but in comparison to using higher bus widths it's still relatively cheap. GDDR5 can probably reach frequencies of around 5GHz, with a 256bit bus it means 160GB/s, which is plenty of bandwidth. Unless you really need more than that, using wider buses isn't necessary.[/QUOTE] Sorry about the misused of the words or whatever. Also yeah for somebody who has a little more background knowledge on this subject.
Wohey, bandwidth vs bit rate wars.
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