Pci-express 2.0 Backwards Compatibility Confusion

Adventure Man

Adventure Man

New Member
Hey guys, I have a question as to the backwards compatibility of pci-express 2.0 with the older pci-express 1.0a specification. My motherboard which I got a few days ago has the older 1.0a spec. My motherboard is a Biostar P4M900-M4 ver.6.x with latest Bios from this September. Here is the website for that motherboard: http://www.biostar.com.tw/app/en-us/mb/content.php?S_ID=283

I would like to purchase (and install on this motherboard) either an 8800GT,8800 GTS from nvidia or 3850,3870 from ati, all four of which use the new pci-express 2.0 specification and require motherboards with pci-express 2.0.
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=10007125
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=10007249
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=10007405

I've heard so many conflicting reports, yes it is compatible, no they are not compatible etc.... Then I see some people whose older mobos with 1.0a specification worked with 2.0 video cards. AND I see some people whose older mobos with 1.0a did not work with an 8800GT. Can we just settle this issue with a simple yes/no or is the answer mobo specific, or is this just ultra complex?

Lastly, is it just a BIOS update that is needed to make these two specifications more compatible?

Thanks a bunch for your time guys.

A.M.
 
"PCIe 2.0 is not completely backward compatible with PCIe v1.x. Graphic cards and motherboards designed for v2.0 will be able to work with v1.1 and vice versa, however v2.0 cards will not work in v1.0 and v1.0a motherboards."

Pulled from the Wikipedia.

I've heard otherwise though. Wikipedia might be wrong, as it used to say it was fully backwards compatible. Someone might have altered it. Something like this, seems to give enough proof that it will work
 
Last edited:
UPDATE:

I got an email from tech support at Biostar. The pci-express 2.0 video cards WILL NOT work on this particular motherboard. Stick with regular pci-express x 16.

A.M
 
From what I have read, PCI 2.0 video cards will work in PCI 1.1 boards, but at 1.1 speeds. You will not get the full effect of the new 2.0 cards until you get a motherboard that supports 2.0.
 
Yes it is backward compatible with 1.0 or 1.1
From PCISIG
http://www.pcisig.com/news_room/faqs/pcie2.0_faq/

Q4: It sounds as if both speed grades are supported in the PCIe 2.0 specification?
A4: The PCIe Base 2.0 specification supports both 2.5GT/s and 5GT/s signaling rates, in order to retain backward compatibility with existing PCIe 1.0 and 1.1 systems. Aside from the faster bit rate, there are a number of improvements in this new specification that allow greater flexibility and reliability in designing PCIe links. For example, the interconnect can be dynamically managed for platform power and performance considerations through software controls. Another significant RAS feature is the inclusion of new controls to allow a PCIe link to continue to function even when some lanes become non-operational.
Q5: Then PCIe 2.0 must be backward compatible with PCIe 1.1 and 1.0?
A5: Yes. The PCIe Base 2.0 specification supports both the 2.5GT/s and 5GT/s signaling technologies. A device designed to the PCIe Base 2.0 specification may support 2.5GT/s, 5GT/s or both. However, a device designed to operate specifically at 5GT/s must also support 2.5GT/s signaling. The PCIe Base specification covers chip-to-chip topologies on the system board. For I/O extensibility across PCIe connectors, the Card Electromechanical (CEM) and ExpressModule™ specifications will also need to be updated, but this work will not impact mechanical compatibility of the slots, cards or modules. Currently, the PCI-SIG is defining the PCIe CEM 2.0 specification which has been released to members for review at v0.5. There are currently no plans to adapt the PCIe Mini CEM specification for the faster bit rate as the market need has not yet materialized.
 
paratwa said:
From what I have read, PCI 2.0 video cards will work in PCI 1.1 boards, but at 1.1 speeds. You will not get the full effect of the new 2.0 cards until you get a motherboard that supports 2.0.
Click to expand...

They did tests on the new G92 cards, in a 2.0 mobo, and not. No difference. 1.1 bandwidth seems to be enough to sate current 2.0 cards.. you are of course right, when it comes to certain future 2.0 cards.

StrangleHold said:
Yes it is backward compatible with 1.0 or 1.1
From PCISIG
http://www.pcisig.com/news_room/faqs/pcie2.0_faq/

Q4: It sounds as if both speed grades are supported in the PCIe 2.0 specification?
A4: The PCIe Base 2.0 specification supports both 2.5GT/s and 5GT/s signaling rates, in order to retain backward compatibility with existing PCIe 1.0 and 1.1 systems. Aside from the faster bit rate, there are a number of improvements in this new specification that allow greater flexibility and reliability in designing PCIe links. For example, the interconnect can be dynamically managed for platform power and performance considerations through software controls. Another significant RAS feature is the inclusion of new controls to allow a PCIe link to continue to function even when some lanes become non-operational.
Q5: Then PCIe 2.0 must be backward compatible with PCIe 1.1 and 1.0?
A5: Yes. The PCIe Base 2.0 specification supports both the 2.5GT/s and 5GT/s signaling technologies. A device designed to the PCIe Base 2.0 specification may support 2.5GT/s, 5GT/s or both. However, a device designed to operate specifically at 5GT/s must also support 2.5GT/s signaling. The PCIe Base specification covers chip-to-chip topologies on the system board. For I/O extensibility across PCIe connectors, the Card Electromechanical (CEM) and ExpressModule™ specifications will also need to be updated, but this work will not impact mechanical compatibility of the slots, cards or modules. Currently, the PCI-SIG is defining the PCIe CEM 2.0 specification which has been released to members for review at v0.5. There are currently no plans to adapt the PCIe Mini CEM specification for the faster bit rate as the market need has not yet materialized.
Click to expand...

I think we've all seen that, but it doesn't seem to be 100% conclusive. As seen above Biostar says it won't work in his 1.0a mobo (if they're not wrong). I guess it's just a certain (small) number of 1.0 motherboards that have a problem with 2.0, as most people report it works fine. Well either that or it's just a bad rumor, that's got Biostar believing.
 
hermeslyre said:
They did tests on the new G92 cards, in a 2.0 mobo, and not. No difference. 1.1 bandwidth seems to be enough to sate current 2.0 cards.. you are of course right, when it comes to certain future 2.0 cards.



I think we've all seen that, but it doesn't seem to be 100% conclusive. As seen above Biostar says it won't work in his 1.0a mobo (if they're not wrong). I guess it's just a certain (small) number of 1.0 motherboards that have a problem with 2.0, as most people report it works fine. Well either that or it's just a bad rumor, that's got Biostar believing.
Click to expand...

A few people have tried pci express 2.0 cards in that biostar board, none worked. Trial and error unfortunately was the only way to completely prove biostar was right all along lol
It's a nice motherboard though.
 
I had nothing but problems with PCI 2.0 working for a non PCI 2.0 card with Asus M3a motherboard.
 
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