Use of x16 PCIe slots on Gigabyte GA-P55A-UD4

freemansteve

freemansteve

freemansteve

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Hi, I'm thinking about buying a Gigabyte GA-P55A-UD4.
I have a specific question about the use of the second x16 slot, but cannot get it answered categorically, not even by Gigabyte Support (who I don't think actually exist).

I know all about how x1, x4 etc works, and lane assignment for SLi, USB3 and so on with i5's.

What I want to know is whether anyone can definitively say that they are successfully using a non-graphics card in the second x16 slot. I want to use a single nVidia card in the first x16 slot and a RAID card in the second x16 slot that happens to be a x4 card (which of course fits perfectly in the physical and electronic sense). I don't care about absolute bandwidth and so on, as it's largely irrelevant for me.

There are many postings by the ignorant along the lines of "it's just PCIe - it just works", which is nonsense, and definitely shouldn't influence a buying decision. For example, I have an Asus A8Ne-premium with 2 x16 slots, and you definitely can't run a non-graphics card in the second x16 slot, but it does work perfectly in a x4 slot on that board, as you'd expect, so please, no speculation - actual facts only from experimental data will help me.

If it's inconclusive, I'd like to hear of any similar P55A-type motherboards that are known to do what I need. For other reasons I need the USB3 and 6G SATA capability too, hence my choice of boards is limited.

Thanks
Steve
 
Without sounding ungrateful for your opinion, "pretty sure" is not enough to persuade me to spend £150.

I genuinely understand PCIe (I make products using PCIe, amongst many other related technologies, for a living).

Are you certain the BIOS doesn't prevent the second slot being used for non-graphics as is the case on my Asus mobo?
 
why dont you phone the retailer giving that your gonna purchase the product from them. then at least if it doesnt, you would be well within your rights to send it back.
 
Thanks but I already checked with two major retailers and one didn't respond and the other didn't really know (in a long winded kind of way!) and pointed me to the manufacturer. Gigabyte haven't responded in over a week, and I'd put money on the response being vague and inconclusive if I get one, so I'm rapidly losing the will to live.

Maybe someone at Overclockers.co.uk knows the definitive answer, and if so, I have a credit card burning a hole in my pocket.... I'd even buy one to test myself, so long as I can be guaranteed to get a refund if it doesn't work as I need it to.

I also wanted the revised Rev2.0 board, but the responding retailer said they had no control over what they shipped.

S.
 
Another thing that i would be worried about is that if that second slot is used does'nt that automatically drop the speed in the top slot to 8x?
 
Not concerned about only x8 to graphics card - at gen 2 rates, that's a theoretical 40Gb/s, which is way more than I need for my 250GTS card....

I'd rather get more disk speed with my x4 RAID card & 4 veloci-raptors, hence the original question.
 
I'm certain that it would work. I saw an article a couple of years ago on a review site, saying about the effects of pci 16x and 8x and so on, and they used electrical tape to cover the contacts corresponding to 16x, and the card ran at 8x, and did the same with the other contacts all the way down to 1x. I've also ran a raid card in a 16x lane on a p45 chipset. Admittedly not the same board, but the design is similar. Since the asus was an nforce board, i'd expect the chipset could be the reason it would only accept a graphics card.
From reading around, it appears most new boards are much less picky about having only video cards in x16 slots. The manual for your motherboard makes no mention of this, and even seems to imply that any cards will work fine. Besides, you can return it if it doesnt work.
 
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I know everyone is trying to helpful, but I know how PCIe lanes work - I build commercial products that use PCIe.

[At the end of the day, all PCIe-based systems are just a bunch of x1 lanes, sometimes geographically grouped (like in x16 slot), but which all connect via a PCIe switch onto one more other buses internal to a CPU.The switch function can be done with one or more discrete chips like PLX chip, or implemented in the chipset (P55 express with 8 PCIe root ports) or indeed in a CPU package. The switching is needed because the aggregate bandwidth of all PCIe lanes is so high they must be arbitrated. The use of any lane or group of lanes can be controlled or assigned by system firmware, which in the case of a PC mobo is the BIOS. In a system that also supports crossfire or SLi, some of the available lanes may need to go through an additional switch chip (e.g. PLX) to make sure there are simply enough lanes available system-wide. The BIOS would be aware of this system complication, and may prevent these lanes being used for other purposes than a graphics subsystem.]

I also am sure that some motherboards DO let you use non-graphics cards with varying numbers of lanes in ANY slot, and I know for sure some motherboards do not. It all depends on the details of their architecture.

So, the one simple thing I need is empirical evidence that the Gigabyte P55A-UD4 specifically can run one graphics card and one non-graphics card in the two available x16 slots. It can be any non-graphics card to prove the point. I want to do this because my x4 card won't fit in any other available PCIe slot 'cos they are all x1 (and therefore physically too small).

I kind of figured someone may have this exact mobo (being popular) and might have tried plugging in a non-graphics card to the second x16 slot, or even that someone could just test it for me. Nothing bad will happen to the mobo or the plug-in card in a test. The only thing that will happen is that one or more cards don't get recognized in the second x16 slot - all goes back to normal when you unplug the non-graphics card - honest.

S
 
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isn't it more down to the chipset than the make of the motherboard thou ?

so if another P55 board can do it, the liklyhood is that others can as well.

i doubt u'll get a definate answer unless there happens to be someone with that board whos using a 4x card
 
"isn't it more down to the chipset than the make of the motherboard thou"

-- No. Motherboards using the same chipset may well have different architectural features and BIOS's - they are not usually pure reference designs like some GPUs are. I think you are right that I need a response form someone using this actual Gigabyte board, or a recommendation for another board that can run non-graphics in the second x16, but still has features like SATA3/USB3.
S
 
If I had any non graphics card pcie cards I'd try it on my p55-ud4 which might give you a clue thou of course it isn't the same board it would maybe give you some idea if another gigabyte board can do it.

Have you tried asking ocuk via a web note? I'm sure they could rig it up and try it?
 
Crowort said:
If I had any non graphics card pcie cards I'd try it on my p55-ud4 which might give you a clue thou of course it isn't the same board it would maybe give you some idea if another gigabyte board can do it.

Have you tried asking ocuk via a web note? I'm sure they could rig it up and try it?
Click to expand...

doubt ocuk will go anywhere near it tbh. why would they want to risk (it's a minute risk but one nontheless) their gear?

btw i'm running a SATA600 4x card in one of my 16x lanes. didn't do anything fancy to get it to work.

if advice, recommendation and reassurance from lots of forum members isn't enough then you're just gonna have to take the plunge and try it yourself.
 
It works!

For anyone interested, I did buy a Gigabyte GA-P55A-UD4 board, which I had running in a hour or so with Win7-32 on a spare disk drive. Got all the latest updates, including latest BIOS - F14.

I then added my Promise 8350 RAID card into the second x16 slot, knowing that the only bad thing would be the card might not be recognized (given that I already know some m/brds do not recognize non-graphics cards in some x16 slots intended for for SLi). As luck would have it, it burst into life after a reboot and was immediately recognized by Win7 which loaded drivers.

It was then a simple matter to clone disks from my original scratch disk onto a newly created 4-disk array (I hate dicking with separate drivers). Shutdown, removed scratch disk, rebooted and all fine. Note that I have a modest 250 GTS nVidia card in the first x16 slot, and am unable to discern any performance hit (the graphics win score is the same before and after, but of course I get a much better disk rating now).

Since I play FPS games at max res, but don't get all concerned about frame rates (enough is enough here) or turning on all possible graphics widgets, I'm reasonably sure I'm unlikely to be losing anything by having a RAID card in the second slot.

Since building the system, I finally got a belated response from Gigabyte Tech Support saying that non-graphics will normally work in the second x16 on this board, but couldn't say if a Promise 8530 would or not. And it does !

Quite happy with the board with an i5-750 and Kingston KHX1600C9D3K2/4G DDR3; it's only a moderately fast setup but reasonable value overall. Individual Win7 scores are 7.3, 7.5, 7.0, 7.0 and 6.4 in order. Which means the Promise card is no stunner with 4 drives in RAID-5.

Steve
 
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