Crossfire Bad FPS. PCI Express bottleneck?

[Juliogol]

HI guys,

So I've been struggling to get a R9 280x CF to work properly, but I am about to give up. I think that my problem is that my motherboard has a PCI Express 3.0 at 16x but the other one functions at 2.0 4x when crossfiring.

I think that is why I'm not seeing the two 280x perform as they should. I game at 1080p, mostly BF4 and get 70-110 FPS on medium settings...

What do you guys think, it the PCI at 4x bottlenecking my 2nd GPU so bad that I get these results? If I upgrade the MOBO will I get better FPS?

Rest of my specs:

Core I5 2500k
12 GB RAM
120 GB SSD
Gigabyte h67m-ud2h-b3 Motherboard

I appreciate if you can help me out here!

 

[KingPing]

If i'm not mistaken the 2nd PCIe on a H67 board goes through the chipset (that's why the primary is 3.0 and the secondary is 2.0), unlike the primary PCIe that is connected directly to the CPU, that will surely bottleneck the card, specially a 280X.

For crossfire i would go with a Z68 or Z77 board where both PCIe lanes are connected directly to the CPU.

Edit: IF you grab your MOBO manual and go to the "Motherboard block diagram" page you should see that only the 1st PCIe (X16) is connected directly to the CPU, the 2nd (x4) is connected to the H67 chipset. That alone is a huge bottleneck. Buy a MOBO with both PCIe connected directly to the CPU like a Z68/Z77, before buying one go to gigabyte site and check in the manualk if both indeed are connected directly to the CPU, because that's not the case in some cheap Z68/Z77 boards.

 

[newtekie1]

Upgrading to a Z68/Z77 board will also allow you to overclock that 2500K, which you will need to do, otherwise it will hold you back with two 280x's at 1080p.

 

[Law-II]

Hi

Gigabyte h67m-ud2h-b3 rev 1.0 & 1.1
Supports PCIe x16 2.0 Only

Source pdf manual here

Intel 2500K CPU officialy Supports PCIe 2.0 [unofficial support for PCIe 3.0 was shown on certain motherboards]
Source CPU - World here

+1 newtekie1 ; z68/z77 and will need to OC the *2500k; [Note: *will need a good quality heatsink & fan]

atb

Law-II

 

[droopyRO]

I agree with the above, get a Z77 board, a good CPU aftermarket cooler, overclock the i5 to at least 4 Ghz also what PSU do you have ?
PS: fill in your system specs.

 

[Shambles1980]

my 2500k will only do pcie 2.0 on my 3.0 board. pretty sure you need a 3xxx to get 3.0

 

[Jetster]

Its not the PCI-E 2.0 that's the problem its the chipset and the board. A Z77 even with it running PCI-E 8x8 2.0 should not bottleneck

You should get 80 -100 at high setting. Overclock that 2500K to 4.4 (with a proper cooler)

 

[Aquinus]

It's also worth noting that if the first card stays at 16x when both are installed, those 4 lanes are going through the PCH, which just adds latency to the problem. So yes, the 4x PCI-E lane is potentially a problem. I would find yourself a Z77 board or something so you would at least have both cards using the CPU's PCI-E root hub. Two 8 lane PCI-E slots @ 2.0 should be enough. It would solve this problem rather quickly both PCI-E lanes wise and overclocking wise.

 

[Juliogol]

If i'm not mistaken the 2nd PCIe on a H67 board goes through the chipset (that's why the primary is 3.0 and the secondary is 2.0), unlike the primary PCIe that is connected directly to the CPU, that will surely bottleneck the card, specially a 280X.

For crossfire i would go with a Z68 or Z77 board where both PCIe lanes are connected directly to the CPU.

Edit: IF you grab your MOBO manual and go to the "Motherboard block diagram" page you should see that only the 1st PCIe (X16) is connected directly to the CPU, the 2nd (x4) is connected to the H67 chipset. That alone is a huge bottleneck. Buy a MOBO with both PCIe connected directly to the CPU like a Z68/Z77, before buying one go to gigabyte site and check in the manualk if both indeed are connected directly to the CPU, because that's not the case in some cheap Z68/Z77 boards.

Upgrading to a Z68/Z77 board will also allow you to overclock that 2500K, which you will need to do, otherwise it will hold you back with two 280x's at 1080p.

Hi

Gigabyte h67m-ud2h-b3 rev 1.0 & 1.1
Supports PCIe x16 2.0 Only
View attachment 57307
Source pdf manual here

Intel 2500K CPU officialy Supports PCIe 2.0 [unofficial support for PCIe 3.0 was shown on certain motherboards]
Source CPU - World here

+1 newtekie1 ; z68/z77 and will need to OC the *2500k; [Note: *will need a good quality heatsink & fan]

atb

Law-II

I agree with the above, get a Z77 board, a good CPU aftermarket cooler, overclock the i5 to at least 4 Ghz also what PSU do you have ?
PS: fill in your system specs.

It's also worth noting that if the first card stays at 16x when both are installed, those 4 lanes are going through the PCH, which just adds latency to the problem. So yes, the 4x PCI-E lane is potentially a problem. I would find yourself a Z77 board or something so you would at least have both cards using the CPU's PCI-E root hub. Two 8 lane PCI-E slots @ 2.0 should be enough. It would solve this problem rather quickly both PCI-E lanes wise and overclocking wise.

Thanks so much fot the replys guys!! So looks like I am not mistaken to think that the PCI Express at 4x is the problem with my crossfire setup. So all your advices is that I should upgrade my MOBO, but, and sorry for my noobie question, what motherboards do have PCI express at, at least, 8x and support my cpu? As you said, with my actual MOBO I can't overclock the CPU that much because it limitates the multimplier to 37x. I do have a nice cooler, the Coolermaster Hyper 212 so I could get more juice out of the CPU but just Can't because of the motherboard. PSU is a Cooler Master Silent Pro 750w.

When I check at benchmarks with my CF setup, for expample I see 146 FPS avergae con BF3, Ultra Quality with 4x AA and I am only getting 60-80 FPS, and it doesn't change if I set the quality to medium or high

 

[Law-II]

Hi

what motherboards do have PCI express at, at least, 8x and support my cpu?

as previously mentioned chipset "z77" Examples: here select a Skt LGA1155 motherboard that fits with your budget and has the features you require; may need to refer to specifications tab for details:

Example:
1 x PCI Express x16 slot, running at x16 (PCIEX16)
* For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.

1 x PCI Express x16 slot, running at x8 (PCIEX8)
(The PCIEX16 and PCIEX8 slots conform to PCI Express 3.0 standard.)
* The PCIEX8 slot shares bandwidth with the PCIEX16 slot. When the PCIEX8 slot is populated, the PCIEX16 slot will operate at up to x8 mode.

(* Whether PCI Express 3.0 is supported depends on CPU and graphics card compatibility.)

atb

Law-II

 

[Juliogol]

Hi



as previously mentioned chipset "z77" Examples: here select a Skt LGA1155 motherboard that fits with your budget and has the features you require; may need to refer to specifications tab for details:

Example:
1 x PCI Express x16 slot, running at x16 (PCIEX16)
* For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.

1 x PCI Express x16 slot, running at x8 (PCIEX8)
(The PCIEX16 and PCIEX8 slots conform to PCI Express 3.0 standard.)
* The PCIEX8 slot shares bandwidth with the PCIEX16 slot. When the PCIEX8 slot is populated, the PCIEX16 slot will operate at up to x8 mode.

(* Whether PCI Express 3.0 is supported depends on CPU and graphics card compatibility.)

atb

Law-II

Thanks again! Any recommendations in particular? I am kinda noobie when it comes to MOBO

 

[eidairaman1]

GCs need at least 8X speed on both slots to work correctly

 

[Aquinus]

GCs need at least 8X speed on both slots to work correctly

I bet a 280X on 4x @ 3.0 probably would do okay, but that isn't the case here. A graphics card could "work correctly" with a single PCI-E lane, but it wouldn't be very performant, much like how you can run a GPU on a PCI slot, just don't expect a whole lot out of it.

 

[MxPhenom 216]

upgrade to z77 board. Pretty sure all mid range boards support 8x/8x CF and the 2500k for sure. You might have to buy used though. I'd recommend the Gigabyte z77 up4 or 5.

 

[Law-II]

Hi

Any recommendations in particular?

General Advice
Make sure have right tools for the job
New thermal paste for the CPU [pea sized blob in middle of the CPU heat spreader]
**Backup all important data** on current hdd/ssd

Note: If get a chance go here fill in system specs hardware manufacturers brand names ,make, model & OS

atb

Law-II