PCI-e 16x graphics card installed to a PCI-e 1x slot?

[PingSpike]

The other way around, the shorter card in the longer slot is of course possible. But I was reading the entry for PCI Express on wikipedia and it said that while the cards may not physically fit, they are electrically compatible and the link would be negotiated down to 1x speeds. I then read a forum post by a user on google (which I now cannot find, god damn it!) where he said that he had an adapter that let him install a 16x card into a 1x or maybe 4x slot (on I believe a server motherboard). He said he had previously was just going to break off the end of the connector on the motherboard, sounding sure this would work, but the extender was a cleaner solution.

Add more credence to this idea was a toms hardware article that compared performance of 1x-16x on graphics cards...the testing was done by taping off parts of the cards interface.

My motherboard has a spare 1x slot and a traditional 16x slot. There is a 8800gts in the 16x. I would like to install a x800 series card in the 1x slot, and have a seperate windows install that uses that as its primary card for playing older games. (The 8800 cards and the newer ati cards don't get along great with some of my older 3d games) There will be a performance hit running at 1x...but these are pretty old games (Thief series, System Shock II) and the hit wasn't as bad as I thought based on the tom's review.

Is this possible? It seems the adapter would be preferable...but I'm not above a little ghetto modding.

 

[cmdrdredd]

Originally posted by: PingSpike
The other way around, the shorter card in the longer slot is of course possible. But I was reading the entry for PCI Express on wikipedia and it said that while the cards may not physically fit, they are electrically compatible and the link would be negotiated down to 1x speeds. I then read a forum post by a user on google (which I now cannot find, god damn it!) where he said that he had an adapter that let him install a 16x card into a 1x or maybe 4x slot (on I believe a server motherboard). He said he had previously was just going to break off the end of the connector on the motherboard, sounding sure this would work, but the extender was a cleaner solution.

Add more credence to this idea was a toms hardware article that compared performance of 1x-16x on graphics cards...the testing was done by taping off parts of the cards interface.

My motherboard has a spare 1x slot and a traditional 16x slot. There is a 8800gts in the 16x. I would like to install a x800 series card in the 1x slot, and have a seperate windows install that uses that as its primary card for playing older games. (The 8800 cards and the newer ati cards don't get along great with some of my older 3d games) There will be a performance hit running at 1x...but these are pretty old games (Thief series, System Shock II) and the hit wasn't as bad as I thought based on the tom's review.

Is this possible? It seems the adapter would be preferable...but I'm not above a little ghetto modding.

No

 

[ninjit]

It should be possible, because the PCIe spec calls for compatibility with any number of links.

However, physical connectors would be the limitation here.

If a motherboard had x16, x8, x4, and x1 type electrical PCIe connections, but all x16 type physical connectors, then you would be golden: you could plug any card, anywhere, and it should work at whatever the link speed is.

I'm also not sure I believe the "adapter" story.
That would only work if there was no backpanel to worry about (i.e. an open case with just the motherboard). Otherwise with any sort of adapter, the card would either be raised slightly, or offset to one side - in either case it would no longer mount properly to the back of the enclosure.

 

[SunnyD]

It is possible - that's how PCIe is designed. However, you run into the issue that the actual PCIe socket usually is designed to PHYSICALLY accept a certain card - 1x, 4x or 16x (most all electrical 8x connections use 16x sockets). There were a few motherboards (namely Asus) that used a mechanical 4x socket that was open-ended... in other words it would let a larger connection "hang out" of the socket and not impede it from being plugged in. It was electrically either a 1x or 4x connection, but you could happily put a 16x card in there and run.

Now the real issue to raise is the power planes - as the smaller connections I believe provide less power, meaning that your intensive video cards won't work too well.

 

[Peter]

Two points here:

(1) the physical connector won't fit, and extenders will make the assembly too high to fit into the case (not to mention the slot bracket into the slot).

(2) the power allowance in a 1x slot is way lower than for a 16x.

 

[Nanobaud]

Here's your adapter:

16x card into 1x slot Adapter

I also recall it being said you can cut a slot in the back of the 1x slot and plug-in the 16x card, but this adapter seems to route some power and/or ground to the back pins, so there are probably some issues there.

Also, as mentioned above, you should consider total power requirements. You might even try calling support at the adapter supplier and see if you luck out and get someone who knows these answers.

nBd

 

[PingSpike]

Yeah, I found another adapter elsewhere for $26 as well.

Regarding the riser/adapter fitting. That could potentially pose some challenges, but I do own a dremel. At any rate I think all that would be required would be a standoff or two, and maybe some washers to assure the back bracket for the card could be secured. If the connections coming out of the back caused problems, I think I could cut out the offending part of the case.

The power thing is the real problem. I know some cards draw all the power they need right from the pci-e slot...but most seem to require an additional connection to the power supply. Will this connection this connection alleviate this concern? Or does it require both to function?

Again, Tom's hardware seemed to run cards in a 16x slot without issue with everything taped so that only the 1x connection was made. Is all power draw coming from there? (the 1x pins) Or maybe this wasn't a concern because of the PSU power supply connection? They used an x600?, x800xt and an nvidia 6800 series card and tested them all with 1x-16x so it seems like this power connection may not be a big concern?

 

[Throckmorton]

It's been done. I remember an article from back when PCIE was new. Some website taped off most of the connectors, and it worked on the 1x gold fingers.

 

[hans007]

it should work...


you could just buy an x1 card, there are a few out there but they are expensive.

some boards even have an x4 with the end "open" so x16 will fit. you will proabbly not be able to run a very fast card though as x1 only hsa like 20 watts going to it compared to x16's normal 75watts.

you'd have to basically just cut the end ofthe slot open very carefully without damaging the pins.

 

[PingSpike]

I guess the next step is to buy one of those adapters and try it with my wife's x850xt and see what happens. I checked last night, and my motherboard has a large jumper block next to the pci-e 1x slot which I think the part of the pci-e card that would be "hanging out" would probably run into.

 

[PingSpike]

Tom's link to the games benchmarks for different pci-e bandwidths, for the curious. They did a recent follow up with a 8800gts and the results were not pretty. The newer cards suffer a small performance hit even going to 8x, and it got much worse after that.

 

[PingSpike]

I doubt anyone cares to much about my little experiment's results, but I really couldn't find much info on this so I thought I'd update on where I'm at.

My motherboard is the epox GLI board, socket 939, uli chipset (same as the famous asrock dual board) and I really like it. It does SLI with both slots at 8x. I only have one video card though, a 8800gts which does take a bit of a performance hit running at 8x according to tom's newer pci-e bandwidth benchmarks. But I wanted a second video card that plays older games (nvidia has broken older games with the 8 series...in particular the thief series and system shock II which both use the same graphics engine) so I thought of putting something else in for those games.

Anyway, the first thing I tried was running a video card in the second slot without setting the machine to 8x by 8x via the jumpers. On most nforce4 boards the second slot should function at 1x pci-e with this setting. 1x pci-e does impact performance on older cards (I've been looking at the x800 ati series mostly) but that shouldn't really amount to much on such an old game. But no dice in my case, based on my manual and testing, it appears for this particular motherboard the second slot is turned off entirely with the jumpers set to single card. I would get post beep codes which surely indicated no video present...I couldn't even get windows to detect the card when using my 8800gts as the primary to get into windows.

But, the motherboard does feature another single, true 1x pci-e slot. This was more troublesome route to consider, since I had hopes the second pci-e slot was wired with the 75watt power that full blown 16x slots use. Regular pci-e 1x slots supposedly only supply 25 watts, according to the spec. However, its possible this limitation (if it even exists in my case) can be worked around using a card with an external power connector...I have no idea how cards decide where to get power from and when.

So, I needed an adapter to plug the video card into this slot. I couldn't just cut the back out and let the card hang over because there was a big jumper block behind it. adexelec.com appears to be the company that supplies the adapter to other retailers, and despite being what looks like a wholesale website they sell single pieces to customers. The necessary piece was $25 + shipping...which is still a pretty big ripoff, but better then elsewhere. They were quick to respond to my request and shipped out the next day however, so overall I was pretty happy with them. I realize the adapter is a unique item so its going to be marked up.

Anyway, the adapter arrived to today. I installed it with a x850xt and it booted up! Finally! In windows cpu-z reported the negotiated speed as 1x pci-e. I ran 3dmark 2001 and got 21747. I ran it again afterwards with the card in the 16x slot and got 26941...so there's a solid performance hit of around ~20% there. But it is running at basically AGP 1x speeds. So, there you go...at least for now, this idea is feasible. The x850xt should use enough power at load that the external power connection must be making up for the weak pci-e 1x slots 25watts. Either that or the 1x slot has extra power for some reason (seems unlikely).

Now I have to solve the last problem: How to mount the card. The pci-e slot is close enough to the 16x slot that I can't install the 8800gts at the same time (the silencer on the x850xt has a rear ramsink that sticks out the back and runs into the big cooler on the 8800gts) and even if I changed the cooling on the ATI card, the card would cover up the fan intake pretty badly on the 8800gts card. Not to mention the fact that I had to zip tie the card to the expansion slots and the VGA port was blocked and unusable after the lift.

The solution I think, will be buying...another adapter! The same company offers a ribbon cable extender, which should give freedom to place the card in a better location. I'll probably build a small wooden stand and screw it into the inside of the case.

 

[bryanW1995]

sweet...if they ever make a "spencer for hire" movie you'll get my vote