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me

join:2002-12-08
Iapetus

1 edit

Using only the second PCIE x16 same speed ? for video card

I need to have access to 3 PCI-e 1 slots but the main video card slot covers one of them. However, there is a second PCI-e x16 slot for a video card.

I need help choosing which board to choose to allow me to use the second PCI-e slot in x16 mode as my only video card.

The processor is i7-2600k (easy OC preferred)
XFX Radeon Double D HD-687A

»www.microcenter.com/product/3934···herboard
»www.microcenter.com/product/3875···herboard
»www.newegg.com/Product/Product.a···13128546

What confuses me is details like this
PCI Express 3.0 x16 - 2 (x16, x8)
- I can use either and have x16 or do I have to use the main (different colored) slot?

or
PCI Express 2.0 x16 - 2 (x8, x4)
-If I use the second slot alone will it be x16 ( I know it is x4 if both are used)


koitsu
Premium,MVM
join:2002-07-16
Mountain View, CA
kudos:23

2 edits

Always refer to the manufacturer's web site + user manual for details of this nature.

quote:
2 x PCIe 3.0/2.0 x16 (x16 or dual x8) *3
1 x PCIe 2.0 x16 (x4 mode, black) *4

*3: PCIe 3.0 speed is supported by Intel 3rd generation Core processors.
*4: The PCIe x16_3 slot shares bandwidth with PCIe x1_2 slot. The default setting is x2 mode. Go to the BIOS setup to change the settings.

And of course a motherboard photo.

You need to refer to the User Manual to know where the x16_1, x16_2, and x16_3 slots are. They are labelled on page 2-2 (PDF page 22).

Simply put, this means (please read slowly, do not skim):

1. The dark blue and white/grey PCIe x16 slots support PCI Express 3.0 and 2.0

2. The dark blue PCIe x16 slot runs at x16 speed if the white/grey PCIe x16 slot is not populated, otherwise it runs at x8 speed

3. The white/grey PCIe x16 slot runs at x16 speed if the dark blue PCIe x16 slot is not populated, otherwise it runs at x8 speed

4. The black PCIe x16 slot supports PCI Express 2.0 and runs at a maximum of x4 speed (e.g. if a PCIe x16 card is inserted into this slot, it will only run at x4 speed)

5. The black PCIe x16 slot and white/grey PCIe x16 slot share bandwidth (limited to x2 speed).

So simply put: you can safely put your video card in the white/grey PCIe x16 slot and use it without any performance hit.

However, if you put anything in the dark blue PCIe slot then your white/grey PCIe slot will run at x8. If the card in the dark blue PCIe slot happens to be something lower than x8 speed, I'm under the impression that only that slot/card will run at that speed. Meaning: if you had a x1 speed card in the dark blue slot, and a x16 speed card in the white/grey slot, then the dark blue slot would run at x1, and the dark blue slot would run at x8.

Also, if you put anything in the black PCIe slot, then your white/grey PCIe slot will share bandwidth with the black slot (limited to x2 speed).

My recommendation: keep your video card in the dark blue x16 slot. The remaining slots you should use for PCIe x1 cards should be either (a) the PCIe x1 dark blue slots, or (b) the black PCIe x16 slot. Otherwise you will suffer speed/performance hits.

In effect, the motherboard manufacturer did not wire enough physical lanes to maintain this number of PCIe slots, so lots of slots end up "sharing" things. This is very common.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.

Extide

join:2000-06-11
84129
reply to me

Also keep in mind you need an Ivy Bridge for PCIe 3.0 (3000 series CPU). Sandy Bridge (2000 series CPU) only supports PCIe 2.0.


sk1939
Premium
join:2010-10-23
Mclean, VA
kudos:10
Reviews:
·T-Mobile US
·Verizon FiOS
reply to me

I recommend this board: »www.microcenter.com/product/3875···herboard

Out of the ones you have listed. As far as video cards go, if you have more than one card on the Sandy or Ivy bridge platform you will run at PCI-e x8 speeds for each card, that's just how the platform is architected. Otherwise usually the top slot is x16, but your motherboards manual will tell you more.



El Quintron
Resident Mouth Breather
Premium
join:2008-04-28
Etobicoke, ON
kudos:4
reply to koitsu

That was a great writeup BTW...



koitsu
Premium,MVM
join:2002-07-16
Mountain View, CA
kudos:23

Thanks. I hope I got it all correct/right! I might be misunderstanding something about the "shared bandwidth" between the black and white/grey slot, but the rest should be correct for sure.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.



me

join:2002-12-08
Iapetus

Thanks for the explanation. Reading it without the pic the first time was a bit confusing

To sum it up, whether I use the first or second PCIe x16 slot, adding anything to the free slot will reduce the speed.

Is the first or dark blue slot immune to this effect? Can I put a PCIe x1 card in the second PCIe x16 (grey) without degrading the speed of the primary PCIe x16 slot (dark blue)?



me

join:2002-12-08
Iapetus
reply to me

Basically, I need to be able to use 3 PCIe slots in x1 mode and I don't want my video card x16 performance affected.

Many boards cover up a PCIe x1 slot under the video card. (dual slot)

Please help me choose that card.


sk1939
Premium
join:2010-10-23
Mclean, VA
kudos:10
Reviews:
·T-Mobile US
·Verizon FiOS

The board I suggested has 3 PCI-e x1 slots.

Your video card will run at x16 performance so long as you don't have another video card plugged into the other x16 slot. If you do, it will only run at x8 speeds, HOWEVER there is no noticeable difference at this point in time between x8 and x16 (3% difference or so) for graphics performance.

Beyond that, you can use an x1 card in the x4/x16 mechanical slot.



koitsu
Premium,MVM
join:2002-07-16
Mountain View, CA
kudos:23

To expand on sk1939 See Profile's post mentioning the GA-Z77X-UD3H -- meaning I'm trying to make it more clear for you, me See Profile -- so please read slowly/thoroughly again --

First, see the zoomed in picture of the GA-Z77X-UD3H board and read the silkscreening labels on each of the slots (either above or along the edge of the slot). I'll describe each slot to you, from RIGHT TO LEFT:

PCIEX1_1 -- PCIe x1 slot, supporting up to x1 speed
PCIEX16  -- PCIe x16 slot, supporting up to x16 speed
PCIEX1_2 -- PCIe x1 slot, supporting up to x1 speed
PCIEX1_3 -- PCIe x1 slot, supporting up to x1 speed
PCIEX8   -- PCIe x16 slot, supporting up to x8 speed
PCI      -- standard PCI slot
PCIEX4   -- PCIe x16 slot, supporting up to x4 speed
 

We assume your graphics card requires one PCIe x16 slot and takes up 2 physical backplane/chassis slots (this is common today), which means if it was installed in PCIEX16, it would physically block PCIEX1_2 from being used.

And if you install a PCIe x1 card in PCIEX8, your PCIEX16 slot drops to x8 speed, which you don't want either.

Following so far?

This board will meet your requirements without any speed loss/degradation if you do the following:

* Install graphics card in PCIEX16
* Install PCIe x1 card in PCIEX1_1
* Install PCIe x1 card in PCIEX1_3
* Install PCIe x1 card in PCIEX4

How does this work / why this configuration?

1. By leaving slot PCIEX8 empty, this ensure PCIEX16 stays at x16 speed,
2. Never populate slot PCIEX4 with a x2, x4, x8, or x16 card -- otherwise you will disable/turn off the PCIEX1_1, PCIEX1_2, and PCIEX1_3 slots, since they share bandwidth with the PCIEX4 slot.

Make sense?

Finally, I should note this same configuration will work on the GA-Z77X-D3H (note the model string difference) too.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.

sk1939
Premium
join:2010-10-23
Mclean, VA
kudos:10

To speak on the difference between the D3H and the UD3H, it boils down to having eSATA ports or not, that's it.



me

join:2002-12-08
Iapetus

1 edit
reply to koitsu

Thanks that clears up some things for me.

Between D3H and the UD3H I think UEFI BIOS is also a difference.

Edit:
Placing anything including PCEe x1 on PCIEX8 will affect PCIE16?



koitsu
Premium,MVM
join:2002-07-16
Mountain View, CA
kudos:23

said by me:

Between D3H and the UD3H I think UEFI BIOS is also a difference.

Incorrect:

GZ-Z77X-UD3H rev 1.0 -- »www.gigabyte.com/products/produc···=4153#ov
GA-Z77X-D3H rev 1.0 -- »www.gigabyte.com/products/produc···=4144#ov
GA-Z77X-D3H rev 1.1 -- »www.gigabyte.com/products/produc···=4325#ov

You can see if you scroll down the page, all of them are completely UEFI-based ("UEFI DualBIOS"). There is no classic BIOS for any of these boards.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.


me

join:2002-12-08
Iapetus

2 edits

I went with the GA-Z77X-D3H rev 1.0 without knowing about that v1.1 is available.
This model has more SATA connections (which I may need). For $40 dollars less after rebate, I decided against UD3H.

Version 1 and 0 are basically the same except for a PCIe 3.0 issue.

GA-Z77X-D3H rev 1.0
1 x PCI Express x16 slot, running at x8 (PCIEX8)
* 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.
(The PCIEX16 and PCIEX8 slots conform to PCI Express 3.0 standard.)
* PCIE Gen.3 is dependent on CPU and expansion card compatibility.

GA-Z77X-D3H rev 1.1
1 x PCI Express x16 slot, running at x8 (PCIEX8)
(The PCIEX16 and PCIEX8 slots conform to PCI Express 3.0 standard.)
* Whether PCI Express 3.0 is supported depends on CPU and graphics card compatibility.
* 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.


Also 1 x 8-pin ATX 12V power connector for the UD3H
and 4 for D3H. (not sure if this will affect overclocking)

Comparison chart
»www.gigabyte.com/products/compar···153,4144

These would have been nice to have on my board
1 x power button
1 x reset button
1 x Clear CMOS button
1 x Voltage Measurement Points
1 x BIOS Switch



me

join:2002-12-08
Iapetus
reply to koitsu

said by koitsu:

How does this work / why this configuration?

1. By leaving slot PCIEX8 empty, this ensure PCIEX16 stays at x16 speed,
2. Never populate slot PCIEX4 with a x2, x4, x8, or x16 card -- otherwise you will disable/turn off the PCIEX1_1, PCIEX1_2, and PCIEX1_3 slots, since they share bandwidth with the PCIEX4 slot.

This limitation of the PCIEX4 slot leads me to my main question and concern. Can I use the second PCIEx16 slot for my video card without a reduction in speed. I will leave the first PCIEx16 slot empty. This way I have 3 PCIe x1 slots free.


koitsu
Premium,MVM
join:2002-07-16
Mountain View, CA
kudos:23

said by me:

Can I use the second PCIEx16 slot for my video card without a reduction in speed. I will leave the first PCIEx16 slot empty. This way I have 3 PCIe x1 slots free.

Yes, you can absolutely do that. I have confirmation of that working correctly/reliably from a colleague of mine in Sweden whose "main" PCIe x16 slot has gone bad (I believe one of the pins in the slot has somehow gotten out of place/bent), so he uses the 2nd PCIe x16 slot without any repercussions. Just make sure you keep the 1st PCIe x16 slot open.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.


me

join:2002-12-08
Iapetus

OT. A friend from Sweden just left my house to head back home...

The fact that they label it PCIE8 makes me wonder although someone already mentioned its not a factor at this time.

Any recommendation on software that displays this information. I will give SIW a try later.



koitsu
Premium,MVM
join:2002-07-16
Mountain View, CA
kudos:23

said by me:

OT. A friend from Sweden just left my house to head back home...

The fact that they label it PCIE8 makes me wonder although someone already mentioned its not a factor at this time.

Any recommendation on software that displays this information. I will give SIW a try later.

I'm sorry, I gave you wrong information -- see, even for me it's hard to keep track!

The 2nd PCIe x16 slot only runs at up to x8 speed. So your x16 card will function/work fine, but will be running at x8 speed. (If you look closely at the slot, you'll see it only has pins for up to x8). If that's not an issue for you, great, problem solved. But if you want your card to run at x16 speed, you'll need to follow what I said above.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.


me

join:2002-12-08
Iapetus

Ok I guess I will make due with the 2 PCIe x1 and the PCIe x4.
BTW. My plan is to connect HDMI streaming cards to connect cameras and use software as a switch. At this point up to 3 cameras is enough.


Extide

join:2000-06-11
84129
reply to me

FWIW: Running your video card at x8 wont slow it down.



me

join:2002-12-08
Iapetus

The video card manual only talks about installing in a x16 primary slot. There is no mention of x8

Please provide a link that say x8 is enough for max performance.

»www.power-color.com/Manual/09010···_ENG.pdf
»www.amd.com/us/products/desktop/···w.aspx#3

JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

Ask and ye shall receive.

»Is pcie 3.0 really worth it?
»www.tomshardware.com/reviews/amd···8-5.html

It's not so much a direct comparison of x16 and x8 because you need to know the PCIe revision. 1.1 had a maximum bandwidth of 250MB/s per lane, 2.0 doubled that to 500MB/s per lane and 3.0 doubles that again to 1GB/s per lane. Thus we have the following:
PCIe 1.1 x16 - 4GB/s
PCIe 1.1 x8 - 2GB/s
PCIe 2.0 x16 - 8GB/s
PCIe 2.0 x8 - 4GB/s
PCIe 3.0 x16 - 16GB/s
PCIe 3.0 x8 - 8GB/s

PCIe bandwidth really comes into play for GPU computing or 3-way and 4-way video card setups. With just 1 or 2 video cards, you won't notice a difference.



me

join:2002-12-08
Iapetus

I used PerformanceTest 7.0 to test this out.

With a PCIE x1 card installed in second port (main port at x8)
-The graphics scores were only off by -1.6% for 2D and -1.2% for 3D

Strange thing is that cpu performance was lower by 9.2% at x8 compare to x16.

For the x8 test I had the case on its side and open (for easy removal of the card)
For x16 test I closed the case and stood it upright. Maybe heat had an effect.


JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

Interesting. The percentage differences on the graphics scores are probably within the acceptable margin of error for the test. Basically further proving x8 is all you really need except in specialty setups. What is intriguing is the CPU difference. That's a noticeable difference. I can't think of any reason why PCIe config of ANY kind would make such a difference.

It's possible heat played a role in the test as you undoubtedly had airflow differences but I can't imagine it got hot enough that quick to make that drastic of a change. If heat did cause that kind of a difference in what I would assume to be a relatively short test (long enough to swap the video card around, test it and swap back?), I'd say you might want to look at your cooling setup and see if there are any problems (dust filled heatsink or fan perhaps?).



me

join:2002-12-08
Iapetus


Two fans
I didn't move the video card. It stayed in primary slot. I stepped it down to x8 by adding a PCIE xl card in the secondary x16 slot.
Removing the extra card bumped it back to x16.

I'm using a good heat sink (Hyper 212) with two 90mm push/pull fans. Temps usually stay constant and low at around 35 degrees

JoelC707
Premium
join:2002-07-09
Lanett, AL
kudos:5

Ahhhh OK, makes sense. And excellent choice on the fan, it's probably the best choice for an air cooler. Still doesn't explain the CPU differences. I wonder if it's repeatable?



me

join:2002-12-08
Iapetus

A second test of the x16 mode resulted in only 4.5 CPU score difference.