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Gigabyte GV-N96TSL-1G
I was considering the fanless Gigabyte GV-N96TSL-1 graphics card in on a
Gigabyte GA-P55A-UD4P motherboard. This board supports (future technology) features USB 3.0 and 6.0 GB/s SATA, however if either of these features are used, the first PCI Express slot goes from 16X to 8X. My question is whether this reduction (to 8x) would be expected to affect the graphics performance of the system. I was thinking that maybe since it is a relatively "slow" card, that it might not--but I really have no idea. Thank you for sharing whatever thoughts you may have concerning this. Bill |
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Gigabyte GV-N96TSL-1G
"Bill" wrote in message ... I was considering the fanless Gigabyte GV-N96TSL-1 graphics card in on a Gigabyte GA-P55A-UD4P motherboard. This board supports (future technology) features USB 3.0 and 6.0 GB/s SATA, however if either of these features are used, the first PCI Express slot goes from 16X to 8X. My question is whether this reduction (to 8x) would be expected to affect the graphics performance of the system. I was thinking that maybe since it is a relatively "slow" card, that it might not--but I really have no idea. Thank you for sharing whatever thoughts you may have concerning this. Bill I should have also mentioned that I was planning to install an Intel 860 CPU in the system. (with no overclocking). |
#3
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Gigabyte GV-N96TSL-1G
Bill wrote:
I was considering the fanless Gigabyte GV-N96TSL-1 graphics card in on a Gigabyte GA-P55A-UD4P motherboard. This board supports (future technology) features USB 3.0 and 6.0 GB/s SATA, however if either of these features are used, the first PCI Express slot goes from 16X to 8X. My question is whether this reduction (to 8x) would be expected to affect the graphics performance of the system. I was thinking that maybe since it is a relatively "slow" card, that it might not--but I really have no idea. Thank you for sharing whatever thoughts you may have concerning this. Bill If the slot ran x8 PCI Express Rev2, that is 8*500MB/sec or 4GB/sec. That is roughly equivalent to twice what you'd get with AGP 8x. The older generation PCI Express Rev1.1 x16 slot, would have given you 16*250MB/sec or 4GB/sec as well. So x8 operation in Rev2 mode, is still pretty good, and comparable to x16 in Rev1.1 mode. If it were to have an impact, which I doubt, it would be at the 5% to 10% level while gaming. Tomshardware did some tests years ago, where they used cello tape, and insulated various numbers of PCI Express lanes. You can use those results, to understand the shape of the performance curve. The effects are worst for one particular kind of benchmark, and not nearly as pronounced on real games. (SpecViewPerf suffers, when PCI E is slowed down) http://www.tomshardware.com/reviews/...ing,927-9.html Such a set of test cases, would need to be repeated for the more powerful processor and GPU combinations available today. I can't guess at what the performance curve would be. The impact should be pretty small, but only a real benchmark series, such as the Tomshardware article, is needed to be sure. ******* On the architecture front, the reason your question is intriguing, is Why would "Northbridge" PCI Express interfaces, have any relationship to what is done on the "Southbridge" ? I downloaded the manual for your motherboard, and I do see the section in question. I don't doubt there is an issue there. ftp://download.gigabyte.ru/manual/mb...a-ud4(p)_e.pdf I also have a copy of the P55 ("Southbridge") spec 322169.pdf, and what is interesting in there, is the chip seems to have integrated clock generation. That might not be the only way to do it. It may be possible to use an external clock generator. My guess is, that they're using the integrated clock generation. That saves money. The P55 spec is 892 pages long, and I'm not going to read the whole thing. Even if I was paid to do it, there wouldn't be enough hours in a day, to read the whole thing, look for every "*" or "Note" in the document, and figure out what evil they're up to. I was not able to find a reference to a register controlling clock generation, due to the limits of the Adobe Acrobat version 9 PDF reader (piece of crap). I wish Intel would use an older version of PDF compatibility, so I could use an older version of Acrobat. The P55 has two PCI Express Rev2 compliant clock outputs (150pS jitter spec). I can see one output going to PCI Express slot 1. The second clock output would go to the PCI Express switch chip, which routes the remaining x8 of bandwidth, to either the first or second video card slot. Maybe the switch chip makes more outputs ? We don't even know what chip is used. Great, we have PCI Express Rev2 video slots, and PCI Express Rev1 Southbridge PCI Express interfaces. Now, when Gigabyte wants to run the add-on peripheral chips with PCI Express Rev2 compliant speeds, it needs the low jitter clocks for that. Where the hell are those clocks coming from ? Perhaps it is the lack of good quality clock signals, that causes this limitation, and interaction between Northbridge (Video) and Southbridge (Peripheral) PCI Express interfaces. I doubt it very much, that the PCI Express switch chip, is being used to supply both video and peripherals at the same time - the Gigabyte architecture diagram in the manual seems to discount that. Very peculiar... and sucky. I wonder how much more it would have cost, to use an external clockgen, or if it is even possible ? I don't know why this interaction exists, but it could be because of Intel's half baked built-in clock generator. Anyone who has worked out clock distribution architectures on a PCB, knows that additional clock outputs are golden, and allow amazing things to be done. Cheap out on them, and some poor PCB designer will be sweating gumdrops, trying to make their design work. At the moment, I don't even know how Gigabyte managed to do what they've done. There are devices, that allow buffering and creation of more clock signals. But once you use such a device, you degrade the clock quality. That is why it isn't a trivial matter to solve. ******* I think in the Tomshardware article, you can see it takes a pretty serious degradation of the video slot bandwidth, before it ruins your video performance. In your case, I wouldn't lose any sleep over it. However, if I bought a $600 video card, and it removed even a few percentage points from it, I'd be ****ed - because I want to get my $600 worth of performance. Paul |
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Gigabyte GV-N96TSL-1G
"Paul" wrote in message ... Bill wrote: I was considering the fanless Gigabyte GV-N96TSL-1 graphics card in on a Gigabyte GA-P55A-UD4P motherboard. This board supports (future technology) features USB 3.0 and 6.0 GB/s SATA, however if either of these features are used, the first PCI Express slot goes from 16X to 8X. My question is whether this reduction (to 8x) would be expected to affect the graphics performance of the system. I was thinking that maybe since it is a relatively "slow" card, that it might not--but I really have no idea. Thank you for sharing whatever thoughts you may have concerning this. Bill If the slot ran x8 PCI Express Rev2, that is 8*500MB/sec or 4GB/sec. That is roughly equivalent to twice what you'd get with AGP 8x. The older generation PCI Express Rev1.1 x16 slot, would have given you 16*250MB/sec or 4GB/sec as well. So x8 operation in Rev2 mode, is still pretty good, and comparable to x16 in Rev1.1 mode. If it were to have an impact, which I doubt, it would be at the 5% to 10% level while gaming. Tomshardware did some tests years ago, where they used cello tape, and insulated various numbers of PCI Express lanes. You can use those results, to understand the shape of the performance curve. The effects are worst for one particular kind of benchmark, and not nearly as pronounced on real games. (SpecViewPerf suffers, when PCI E is slowed down) http://www.tomshardware.com/reviews/...ing,927-9.html Such a set of test cases, would need to be repeated for the more powerful processor and GPU combinations available today. I can't guess at what the performance curve would be. The impact should be pretty small, but only a real benchmark series, such as the Tomshardware article, is needed to be sure. ******* On the architecture front, the reason your question is intriguing, is Why would "Northbridge" PCI Express interfaces, have any relationship to what is done on the "Southbridge" ? I downloaded the manual for your motherboard, and I do see the section in question. I don't doubt there is an issue there. ftp://download.gigabyte.ru/manual/mb...a-ud4(p)_e.pdf I also have a copy of the P55 ("Southbridge") spec 322169.pdf, and what is interesting in there, is the chip seems to have integrated clock generation. That might not be the only way to do it. It may be possible to use an external clock generator. My guess is, that they're using the integrated clock generation. That saves money. The P55 spec is 892 pages long, and I'm not going to read the whole thing. Even if I was paid to do it, there wouldn't be enough hours in a day, to read the whole thing, look for every "*" or "Note" in the document, and figure out what evil they're up to. I was not able to find a reference to a register controlling clock generation, due to the limits of the Adobe Acrobat version 9 PDF reader (piece of crap). I wish Intel would use an older version of PDF compatibility, so I could use an older version of Acrobat. The P55 has two PCI Express Rev2 compliant clock outputs (150pS jitter spec). I can see one output going to PCI Express slot 1. The second clock output would go to the PCI Express switch chip, which routes the remaining x8 of bandwidth, to either the first or second video card slot. Maybe the switch chip makes more outputs ? We don't even know what chip is used. Great, we have PCI Express Rev2 video slots, and PCI Express Rev1 Southbridge PCI Express interfaces. Now, when Gigabyte wants to run the add-on peripheral chips with PCI Express Rev2 compliant speeds, it needs the low jitter clocks for that. Where the hell are those clocks coming from ? Perhaps it is the lack of good quality clock signals, that causes this limitation, and interaction between Northbridge (Video) and Southbridge (Peripheral) PCI Express interfaces. I doubt it very much, that the PCI Express switch chip, is being used to supply both video and peripherals at the same time - the Gigabyte architecture diagram in the manual seems to discount that. Very peculiar... and sucky. I wonder how much more it would have cost, to use an external clockgen, or if it is even possible ? I don't know why this interaction exists, but it could be because of Intel's half baked built-in clock generator. Anyone who has worked out clock distribution architectures on a PCB, knows that additional clock outputs are golden, and allow amazing things to be done. Cheap out on them, and some poor PCB designer will be sweating gumdrops, trying to make their design work. At the moment, I don't even know how Gigabyte managed to do what they've done. There are devices, that allow buffering and creation of more clock signals. But once you use such a device, you degrade the clock quality. That is why it isn't a trivial matter to solve. ******* I think in the Tomshardware article, you can see it takes a pretty serious degradation of the video slot bandwidth, before it ruins your video performance. In your case, I wouldn't lose any sleep over it. However, if I bought a $600 video card, and it removed even a few percentage points from it, I'd be ****ed - because I want to get my $600 worth of performance. Paul Thank you your very detailed reply, and the link to TomsHardware article. As you put it, "I'm not going to lose any sleep over the 8x issue". From what I have read, the reason the board works the way it does is becuase of the P55 chip. Evidently there isn't anyway to overcome the shortcoming I mentioned (going to 8x) because of that chip--if one wants more, then they need to spend a little more and go to the X58 chip... I don't do any serious gaming. Occasional adventure game, Google Sketchup. Appears I should be okay with the components I mentioned. I was sort of waiting to see how the Intel X25-M SSD /TRIM issues played out, and I haven't heard much lately--which I guess is a good thing. Peace, Bill |
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