PCI vs. PCI-X

[mmganga]

Hi, are PCI-X cards compatible with PCI slots? Ie. if I have an old(er) motherboard with PCI only and I get a PCI-X card will it work in the current motherboard? Later I'd like to upgrade to PCI-X.

Also what's the consensus on PCI-X vs. PCI-Express?

THANKS!

 

[CheesePoofs]

PCI-X is some high speed server pci bus, is ont compatible with pci, and you don't want it 😉.

pci-e (pci express) isn't compatible either with pci, but its the new standard for graphics cards and other add on cards.

 

[mmganga]

Are you sure regarding this?

I had found a few links which said that PCI-X 2.0 (whatever that means) is backward compatible with PCI!!! Probably it works at PCI speeds, not sure...

THANKS!

 

[CheesePoofs]

Uh .... I could be wrong on that. I know pci-x runs at a much higher frequency than pci, so it could just scale down and support pci. I thought it used a different slot though.

 

[mmganga]

Yeah heh, that's why I asked..between PCI, PCI-X and PCI-Express I am sure one is NOT compatible with the others, but the other two should work...that was my feeling that -X works in PCI only at PCI speeds of course!!!!

 

[ArnoldLayne]

Originally posted by: mmganga
Hi, are PCI-X cards compatible with PCI slots?

Yes, but they will run at PCI speed. PCI-X cards will work in PCI slots and PCI cards
will work in PCI-X slots.

Ie. if I have an old(er) motherboard with PCI only and I get a PCI-X card will it work in the current motherboard? Later I'd like to upgrade to PCI-X.
Also what's the consensus on PCI-X vs. PCI-Express?
THANKS!

PCI Express rules. PCI-X drools.

PCI-X is an outdated shared-bus system that is backwards compatible. PCI-Express uses a more sophisticated packet switched model but is not backwards compatible.

http://www.redbooks.ibm.com/abstracts/tips0456.html?Open
(see PCI/PCI-X/PCI-Express bandwidth comparison at end of article)

http://arstechnica.com/articles/paedia/hardware/pcie.ars/1

 

[ribbon13]

PCI-X is still quite useful. It hardly drools, as its been the only real choice for SCSI HBAs in servers and workstations for a long time. PCIe will certainly replace it, but is still quite new.

I downclock PCI-X Bus A on my Tyan Thunder K8WE to run my sound card.

 

[mmganga]

exactly, I am looking for PCI-X for SCSI stuff!!!!

 

[CheesePoofs]

Oh, I thought you were confusing PCI-X with PCI-e, which is why I said you don't need it.

For what its designed for, it does its job well, but its unnecesery for the average user.

 

[ribbon13]

Yeah, most PCI-X cards will run in a plain PCI bus. PCI gets pwned though

 

[Peter]

The thing to know is that PCI-X uses 3.3V signalling, while the usual 32-bit PCI slots on desktop mainboards use 5V. So if you want to put a PCI card into a PCI-X slot, or vice versa, you might find that the card does not fit the slot - the signalling voltage key preventing you from inserting something that won't cooperate. Most PCI-X cards are still capable of doing 5V I/O too, but there are plenty of PCI cards that don't do 3.3V signalling.

 

[AristoV300]

PCI-X
Developed as a faster PCI bus, this bus revision (PCI Bus revision 2.0) was designed for workstation use, since before PCI-E people realized that the 133mb/s bandwidth PCI offered was pittfull for a RAID10 SCSI card or a dual Fiber optic Network controller. Its bus width is 64bits wide (compared to 32bits on PCI) and comes in 33,66,100 and 133mhz varieties, the Slots look like e-longated PCI slots and are about as large as an ISA slot. It offered the much needed increased bandwidth that network admins needed offering 266mb/s(33mhz) 533mb/s(66mhz), 800mb/s (100mhz) and 1.07GB/s (133mhz) bandwidth, with the advent of PCI-Express this PCI revision is being phased out in favor of newer PCI-E slots. Normal PCI cards that have the notch at the begining of the card slot can be used in PCI-X slots, some are even 66mhz compatible (like alot of PCI video cards) and thus can opterate better in PCI-X slots. Otherwise, normaly the use of a regular PCI card in a PCI-X slot forces the PCI-X bus to slow down to 33mhz (unless the PCI-X slot is on a seperate channel from the rest of the PCI-X slots, which almost always isnt the case) and all other slots will slow down to 33mhz as well.

 

[mofrack]

Originally posted by: Peter
The thing to know is that PCI-X uses 3.3V signalling, while the usual 32-bit PCI slots on desktop mainboards use 5V. So if you want to put a PCI card into a PCI-X slot, or vice versa, you might find that the card does not fit the slot - the signalling voltage key preventing you from inserting something that won't cooperate. Most PCI-X cards are still capable of doing 5V I/O too, but there are plenty of PCI cards that don't do 3.3V signalling.

Exactly. I have an LSI SCSI controller that will run on PCI-X at 133mhz, but since it supports 5V signalling as well as 3.3V, I could run it in my A8N SLI, albeit downclocked to regular ol' 33mhz PCI speeds (which would negate any REAL performance increase I would get from running a SCSI drive setup as opposed to SATA RAID).

 

[Nimrodicus]

ribbon13,

Bringing back a month old topic just for my 2 part question, but starting to get desperate... Would you mind sharing exactly how you're downclocking the PCI-X Bus. Are you referring to the motherboard jumper (66mhz max setting), or is there another way to set it at 33mhz specifically (couldn't find any settings in the BIOS...)?

Part 2 is: Is there any benefit to downclocking the PCI-X bus "manually" as opposed to letting it downclock "automatically" on the K8We if I'm not using SCSI (i.e. will the system slow things down that I wouldn't want to slow down?) I too have the K8We and am trying to use a PCI soundcard in this slot. I'd simply use the 33 mhz PCI slot but the Geforce 6800 Ultra I have in PCI Express slot 1 is so honkin' big it covers it (tests invoving running the single gfx card in the 2cd PCI Express slot did not bear fruit). Thanks much.

Nimrodicus