How to force pcie x16 slot to run at x4 on a GA-790FXTA-UD5?

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How to force pcie x16 slot to run at x4 on a GA-790FXTA-UD5?

Postposted on Mon Jan 14, 2013 1:23 pm

Hi, I got a Revodrive 3 for christmas and I can't seem to get it to run at full speed. Currently its reading at about 225 MB/s which is much lower than it should be. The problem appears to be that the motherboard is restricting the x4 card to x1 when I plug it into the any of the x16 slots of my GA-790FXTA-UD5. I can't seem to find any setting at can force it to run at x4. Any ideas on what I can do?
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Re: How to force pcie x16 slot to run at x4 on a GA-790FXTA-

Postposted on Mon Jan 14, 2013 1:47 pm

What x4 card do you have, and what chipset is on it? The problem may be the card, not the slot. Just because the card has an x4 connector does not automatically mean that a single drive has access to all of that bandwidth.

Edit: Never mind, I didn't realize that this was a PCIe based drive on a card. I thought you were using an x4 PCIe SATA adapter. :oops:

Edit 2: What are you using to benchmark it?
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Re: How to force pcie x16 slot to run at x4 on a GA-790FXTA-

Postposted on Mon Jan 14, 2013 2:23 pm

Have you installed the drivers for the drive?

http://www.ocztechnology.com/drivers/Re ... ive_3_X2_/
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Re: How to force pcie x16 slot to run at x4 on a GA-790FXTA-

Postposted on Mon Jan 14, 2013 2:26 pm

I'm using HD tune to benchmark it, using whatever settings are standard. The x4 card is the Revodrive 3 240GB, not the Revodrive 3 x2 240GB. The solution on other motherboards has been to manually change the speed from x1 to x4 but my motherboard has an "old school" BIOS instead of UEFI. I'm just seeing if there's another way to get it up to speed without buying another motherboard.

W00tstock those are the drivers used when you install windows right? If so, then yes I used those.
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Re: How to force pcie x16 slot to run at x4 on a GA-790FXTA-

Postposted on Mon Jan 14, 2013 2:43 pm

Try bumping the HD Tune block size as high as it will go. TR's review of the RevoDrive 3 X2 showed significant negative performance impact at the default HD Tune block size. Maybe the non-X2 version has the same issue (only worse).
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Re: How to force pcie x16 slot to run at x4 on a GA-790FXTA-

Postposted on Mon Jan 14, 2013 3:00 pm

I would try the revo in the first pcie 16 slot and the gpu in the 3rd if you haven't already. Also i would make sure you were running the latest firmware for the card and the latest bios for the mobo.
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Re: How to force pcie x16 slot to run at x4 on a GA-790FXTA-

Postposted on Mon Jan 14, 2013 7:53 pm

The revodrive is in the first pcie slot and turning the block size up to 8 MB actually hurts the read speed a bit down to about 200 MB/s. I really feel that it's the motherboard doing something, but I have no idea how to alter the automatic lane distribution.
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Re: How to force pcie x16 slot to run at x4 on a GA-790FXTA-

Postposted on Tue Jan 15, 2013 11:27 pm

Well, I feel a little stupid. I went looking some more on the internet about old gpus running at x1 instead of x16 and they said to try changing the pcie clock. After setting it to 110MHz I ran the bench again. To be honest I hadn't actually run the test all the way until today and this is what I got:

Image

Guess how much the hard drive is filled?.....
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Re: How to force pcie x16 slot to run at x4 on a GA-790FXTA-

Postposted on Wed Jan 16, 2013 2:55 am

Hi,
as per PCI-E specifications, if you plug a lower grade (eg: 4X) card into a full 16X slot, the only mandated speed is 1X. Anything better (eg: 2/4X) is the result of optional negotiation between the motherboard chipset and the specific card.

Generally, the optional negotiation works quite well when speacking about video card (eg: plug a 4X card onto a 16X slot and it is very probable that the entire setup works at maximum speed, 4X), but it can ben problematic with other cards.

It is for this (and others) reason that many system BIOS enable you to limit yours 16X slots into something lower. If your motherboard does not have this option, you can try to update both its BIOS and the RevoDrive firmware.

Regards.
www.ilsistemista.net - test & bench :)
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Re: How to force pcie x16 slot to run at x4 on a GA-790FXTA-

Postposted on Wed Jan 16, 2013 6:50 am

Hmm. I'd say the "up to 975 MB/s" read speed spec for that drive is rather misleading then. Looks like it only gets close to that rate when it is reading areas of the drive which have never been written to (which you would not do in normal use).
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