Message boards : GPUs : PCI express risers to use multiple GPUs on one motherboard - not detecting card?
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Send message Joined: 24 Dec 19 Posts: 229 |
the 16x to 16x riser you bought may work since you are only PCIe 2.0, but if it were me I would feel a lot better with the higher quality cable. The 1.0 slot will "work" but I think you will find HUGE performance reductions in doing so. as a comparison to the 16x 2.0 slot, the 1x 1.0 slot has just 1/32 of the total bandwidth. I can't imagine it will run very well. just stick to the 2 cards in my opinion. |
Send message Joined: 25 May 09 Posts: 1301 |
Why do I have to plug them into 16x slots if they are only 1x plugs? You don't - electrically the first 18(?) pins on an x16 are exactly the same as those on an x1 - or at least SHOULD be. The reason for trying in an x16 is to make sure that there isn't something strange with the x1 sockets (and that wouldn't be the first time) |
Send message Joined: 5 Oct 06 Posts: 5129 |
Why do I have to plug them into 16x slots if they are only 1x plugs?Although all the power pins are concentrated in the short section before the key, and are common to all sizes, the motherboard manufacturer is at liberty only to provide enough power tracks between PSU and slot to provide the PCI spec power for that size of slot. And if they are at liberty, they will have saved money by exercising that liberty. Copper is expensive. |
Send message Joined: 24 Dec 19 Posts: 229 |
he sent you the PCIe spec. the information on "what power comes from where" is totally up to the GPU design and how the power connections are sorted on the GPUs PCB and will vary from card to card. On most modern graphics cards the slot power and the PCIe power are totally segregated. something along the lines of [slot power supplying the VRAM and fans] and [PCIe power supplying the GPU core]. some manufacturers might even only power the card LEDs and fans from slot power and put all other loads to the PCIe connectors. You're unlikely to find any documentation on how your specific card is setup without independent testing and measurement. |
Send message Joined: 24 Dec 19 Posts: 229 |
Why do I have to plug them into 16x slots if they are only 1x plugs? technically what Richard wrote is correct, the 1x slots are only speced to supply about 10-30W of power. he shouldn't try plugging a GPU into this with a riser that will pull power from the slot (ribbon style) as it could damage the slot from pulling too much power. yes, the electrical spec about what pins are what voltages are the same. but the designed power is different (other than the obvious differences between bandwidth on the data side) |
Send message Joined: 24 Dec 19 Posts: 229 |
it's also possible that the board simply wont recognize a GPU in the 1x slots. |
Send message Joined: 8 Nov 19 Posts: 718 |
My 2ct, Stay away from 1x to 16x risers if you can. Use $8, 6" 16x to 16x double ribbon extension risers. They're cheap and effective. You'll still connect in 16, 8, or 4x (depending on the Mobo). USB risers (1x to 16x) are good for 1x ports, in case the full size slots are already occupied. After this you might need to reinstall the GPU drivers. |
Send message Joined: 25 May 09 Posts: 1301 |
Great, but if you read the description of what the OP's motherboard has, and what he want to achieve, then you would realise that what you are suggesting will not fully answer his quest. Summary - The motherboard has two x16 slots and a number of x1 slots. He wants to run more than 2 GPUs, he wants to have them air-cooled, and the x16 slots are too close together for his comfort. Thus he needs to be able to use the at least one of the x16 slots with a riser, and the x1 slots will need a riser anyway - and those riser will have to be x1 to x16 because they have to be x1 at the motherboard end. So far he's had no joy in getting the motherboard to recognise anything sitting on a x1 to x16 riser. Ian&Steve has made a few suggestions, and I know he has done a lot of work in getting similar (not identical) systems working. |
Send message Joined: 5 Oct 06 Posts: 5129 |
That may require some nifty work with - probably not - a hacksaw, or a fine cutting tool like a Dremel. By opening the end of the PCIe x1 slot, the x16 riser could be physically inserted into the x1 slot. He'd still have to watch out for power consumption: the sense pin should tell the motherboard that a card is present. But he would still have to investigate and manage the card's actual power draw from each input. It should be possible: his cards have nominal power inputs for 375W (75W from the PCIe slot, plus 2x 150W 8-pin supplementary inputs). The cards he has are rated at 250W average total board power. So there's headroom - it's just a question which input has the spare capacity, and that depends on the manufacturer. To my mind, fitting the dual 8-pin suggests that the bulk of the power will be taken from them: if the full 75W was taken from the motherboard, they could have got away with 1 8-pin and 1 6-pin. But I am not a circuitry designer: it's all supposition, and it might still fry the motherboard. Proceed with extreme caution, and keep a fire extinguisher close at hand. |
Send message Joined: 29 Aug 05 Posts: 15567 |
That may require some nifty work with - probably not - a hacksaw, or a fine cutting tool like a Dremel. By opening the end of the PCIe x1 slot, the x16 riser could be physically inserted into the x1 slot.Before the OP goes this route, let me point out that BOINC Dev does not condone this sort of DIY, and any damages done to hardware are at your own risk, etc. Or blame Richard. I know where he lives. ;-) |
Send message Joined: 24 Dec 19 Posts: 229 |
That may require some nifty work with - probably not - a hacksaw, or a fine cutting tool like a Dremel. By opening the end of the PCIe x1 slot, the x16 riser could be physically inserted into the x1 slot. He'd still have to watch out for power consumption: the sense pin should tell the motherboard that a card is present. But he would still have to investigate and manage the card's actual power draw from each input. actually he can't do that at all. even if he wanted to. the topmost 1x slot is immediately obstructed aft of the slot by the north bridge heat sink. the lower 1x slot is obstructed a little further out by the BIOS battery. he would not be able to fit a 16x card here, maybe enough room for a 8x device though. still poor option to try to use these slots for anything. 1x lane at PCIe 1.0 speeds is just too little bandwidth to be useful on BOINC projects. stick to the two 16x slots only. |
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