Personal computing discussed
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churin wrote:2. Can the two x1 slots be usable regardless of how the three x16 slots are used?
EJ257 wrote:churin wrote:2. Can the two x1 slots be usable regardless of how the three x16 slots are used?
It depends on where the x1 slots are located. If they are too close to the x16 slot and you put a high end video card in there it will physically block the x1. You need to look at a picture of the MB to determine this.
TwistedKestrel wrote:You sorta have the first question answered. For the 3 presumably full length slots, one has only 4 lanes, and two share 16 between them. If you use both of those two, each will only have 8 available to them. If you only use one, that one will have the full 16.
churin wrote:OK, the two x1 slots are always available as long as there is no such physical constraints.
churin wrote:Does (x16/0 or x8/x8, x4) mean (one video card + one x4 card) or (two video cards + one x4 card)? If this is so, then in either case, does it mean only 20 lanes are used by these cards?
EJ257 wrote:On a P67 those other two lanes are typically used for on-board peripherals: ethernet (since most boards use a discrete networking chip rather than adding a PHY to the gigE built into the chipset), USB 3.0 and additional SATA, etc. If we had the make and model of this particular board we could say exactly.The P67 supports up to 8 lanes of PCIe 2.0. Your board is using 6 out of the 8 lanes from the P67. Where are the other 2? You probably need a bigger board because the one your looking at may not have the real estate for those 2 extra x1 slots.
churin wrote:It is true I did not notice any change in video performance, but I wonder why 50% reduction in numbers of lanes available have only " a small impact of performance". Could anyone explain why?
just brew it! wrote:I do not believe the AMD SB950 southbridge provides any additional PCIe connectivity. So on an AMD motherboard with a 9xx chipset the PCIe lanes come out of the northbridge.
anotherengineer wrote:just brew it! wrote:I do not believe the AMD SB950 southbridge provides any additional PCIe connectivity. So on an AMD motherboard with a 9xx chipset the PCIe lanes come out of the northbridge.
I will beg to differ on this one.
My giga 990XA, bottom slot is 16x physical, and 4x wired through the southbridge
http://static.techspot.com/articles-inf ... agramT.png
yes wth indeed
just brew it! wrote:churin wrote:It is true I did not notice any change in video performance, but I wonder why 50% reduction in numbers of lanes available have only " a small impact of performance". Could anyone explain why?
Because 16 lanes is overkill. In most cases 8 lanes are more than enough to keep the GPU fed, since you end up being limited by the CPU and/or GPU, not the interconnect between the two.
churin wrote:I do not see any x16 PCIe coming out of the southbridge on the diagram of 990XA. How should I interpret the diagram?
just brew it! wrote:churin wrote:I do not see any x16 PCIe coming out of the southbridge on the diagram of 990XA. How should I interpret the diagram?
anotherengineer's point was that his 3rd x16 slot is actually only x4, since it is hanging off of the southbridge. Upper left corner of the southbridge in the diagram.
UberGerbil wrote:On a P67 those other two lanes are typically used for on-board peripherals: ethernet (since most boards use a discrete networking chip rather than adding a PHY to the gigE built into the chipset), USB 3.0 and additional SATA, etc. If we had the make and model of this particular board we could say exactly.
churin wrote:I wonder why the PCIe connector is full size even though only x4 card can be used on it. Maybe there are only two different physical sizes for PCIe cards. Is this correct?
EJ257 wrote:UberGerbil wrote:churin wrote:I wonder why the PCIe connector is full size even though only x4 card can be used on it. Maybe there are only two different physical sizes for PCIe cards. Is this correct?
They used a full sized slot to be flexible. I think every size but x2 exist. x8 slots you could find on server boards but I have never seen them on consumer hardware. The cool thing about PCIe is that the power, signaling, and clock are always present on those pins left of the notch. The data lanes are all right of the notch starting with x1 and you can use as many or as little as you need. In your example you can plug a x1 card into that full size slot with only x4. It would only use the first set of lanes and it would work like an x1 slot. Since it is a full sized slot, if you plug a x16 card into it the card will detect only 4 lanes and will only allow the first 4 lanes on the card to be used.
EJ257 wrote:UberGerbil wrote:. . . The cool thing about PCIe is that the power, signaling, and clock are always present on those pins left of the notch. The data lanes are all right of the notch starting with x1 and you can use as many or as little as you need. . . .
churin wrote:EJ257 wrote:UberGerbil wrote:. . . The cool thing about PCIe is that the power, signaling, and clock are always present on those pins left of the notch. The data lanes are all right of the notch starting with x1 and you can use as many or as little as you need. . . .
Aren't the above something useful only for PCIe card designers and not for users?
just brew it! wrote:churin wrote:UberGerbil wrote:. . . The cool thing about PCIe is that the power, signaling, and clock are always present on those pins left of the notch. The data lanes are all right of the notch starting with x1 and you can use as many or as little as you need. . . .
Aren't the above something useful only for PCIe card designers and not for users?
It means cards will work in slots that don't necessarily match the native width of the card. The card may not run at peak performance, or you may waste capabilities of the PCIe slot, but it will still function. That's a useful feature for end users.
churin wrote:I didn't write that -- EJ257 did, and then a nested quote tag got mangled so that it got mis-attributed (see above). Nevertheless, it is technically correct. And I'd point out in the statement the mention of power in addition to signalling and clock, as this is often overlooked or misunderstood: an x1 (or x4 or x8) card has exactly as much power available to it as an x16 card. (Though this mostly doesn't matter, since video cards are the consumer PCIe component that consumes the most power -- and they tend to consume so much they need auxiliary power connectors anyway -- it removes one point of worry when you're thinking about mixing and matching slots and cards).UberGerbil's statement as quoted is about the motherboard circuit design around the PCIe slot. I had difficulty understanding exactly what he meant and thought end users need not be concerned about.
I took a close look at the mainboard and now understand exactly what his statement means.