Gigabyte GA-EP45-UD3P (Intel P45) and Hardware RAID, PCI Express speeds

[SeanTek]

What happens to the PCI Express lanes and card speeds in a P45 mobo when you combine a PCI Express x16 graphics card in the first x16 slot, with an x4 card (non-graphics card) in the other slot? What speed will the cards run at?

I'm upgrading from a P35 since my old mobo died. I'm currently looking at the GA-EP45-UD3P, pairing it with a Radeon HD 4850 card. In a few months, however, I would like to add true hardware RAID to the setup, probably with a 3ware 9650SE-4LPML or similar. Most hardware RAID cards around that price point are PCIe x4; some are x8. However, from what I understand the P45 chipset supports 1x16 or 2x8 only; i.e., if you occupy both x16 slots, they will only run at x8. If the particular card supports PCIe 2.0, then the interface will run at twice the speed thus giving the same bandwidth as x16. Does that mean there will be no loss of bandwidth to the 4850, while still supporting the RAID card at its full speed?

In this case, we can assume that the x4 (RAID) card is PCI Express 1.1. I don't know if that changes how the system will behave.

I found this post but the question there is a little different.

Any other mobos to recommend?

Thanks for any advice!

 

[Chronicbs]

I just asked a very similar question myself and this is how I understand it.

I'm not positive about that chipset, but I think the 8x/8x link is just for crossfire/sli. GA-EP45-UD3P See how it's advertised 16x/8x. both slots should run at those advertised speeds when they are running in single mode, and not crossfire. So you should still have a full 16x in your first slot even when you have a 4x raid card in your 2nd slot.

Technically though, ive read that the 4850 won't even saturate an 8x pci-e lan. It takes a dual gpu card to go past 8x.

 

[SeanTek]

Thanks for the link. It's a very similar question. I think it depends on the chipset. According to this chipset diagram, it looks like there are only 16 lanes that can be used for PCI Express 2.0 graphics cards. (This is also from a post from ViRGE after your post.)

I think the P45 is very similar in this regard: there are only 16 PCI Express 2.0 lanes to the P45 itself, so if anything is in the second slot, the P45 will route 8 of those 16 to that slot.

Here is what the UD3P manual says:

1 x PCI Express x16 slot, running at x16 (PCIEX16_1) (Note 3)
1 x PCI Express x16 slot, running at x8 (PCIEX8_1)
(The PCIEX16_1 and PCIEX8_1 slots support ATI CrossFireX
TM
technology
and conform to PCI Express 2.0 standard.)

(Note 3) If you are installing one PCI Express graphics card, be sure to install it in the PCIEX16_1 slot
for optimum performance. When two graphics cards are installed, the PCIEX16_1 slot will
operate at up to x8 mode.

Of course, it's silent about what happens when the second card is not a graphics card. :frown:

Technically though, ive read that the 4850 won't even saturate an 8x pci-e lan. It takes a dual gpu card to go past 8x.

Can you post a link to that info? Even at 8x, 8x at 2.0 is 16x at 1.x speeds, aka 4 GB/s upstream and 4 GB/s downstream. That's pretty fast...but 8 GB/s each way is faster. Tom's Hardware said that there is not much of a difference between PCIe 2.0 x16 and x8, but there is a difference, and that article is over 9 months old now. They compared the 3850, not the 4850.

 

[spacegoast]

Adding the RAID card will have no bearing on the PCI-E lane speeds. You only need to worry about that when setting up Cross Fire, in which case both gpu's will run at x8 and x8. Even then, there have been several tests showing the difference between x16/x16 and x8/x8 is negligible. Since you have only one video card, it will be the full x16.

 

[serendipity]

I was having this problem with a 4x raid card in a Gigabyte mobo the GA-SP45-UD3P to be exact, the raid card would not be recognized if my PCIE gfx card was plugged in, I tried a PCI ancient card and viola RAID posts, called everyone, Gigabyte said its because that slot ls " so out of curiosity I put the 1x raid card in the x8 sata "Crossfire only slot" to see if the problem was a conflict with my gfx card (evga 9800 gt) or something entirely different and what do ya know the 1x worked. So I'm thinking its safe to assume that it was a conflict of some rare kind. Maybe someone has this answer SeanTek I would like to know your experience.

 

[eagle101]

GA-EP45-UD3P.....system re-boots once in a while,this is my friends system:

GA-EP45-UD3P
wxp/sp3 all updates
e8400
4870/512
sata wd rapture hd
no sound hooked up
bios is default
not oc
he disabled the rpm cpu fan in the bios/and the power save....still was re-booting

any ideas thanks

 

[SeanTek]

serendipity: what RAID card are you using? I have not yet gotten a RAID card as I don't have a present need for it...just thinking of future upgrades. However it sounds like your experience is not good with the 4x RAID card in the separate port, so it would be nice to know what kind you have. Did you call the RAID card tech support? I heard that 3ware cards had some issues but they may have been resolved in a more recent firmware upgrade, but IIRC that was for nVidia chipset mobos, not Intel P45s.

 

[serendipity]

I used the Highpoint 2310 4x that didnt work
and the highpoint 2640x1 that worked