PCI Backwards compatibility

[darkmark327]

If I put a 32-bit 66 MHz PCI card into my normal 32-bit 33 MHz slot, it will work fine, albeit with less bandwidth, correct? I plan on getting a RAID controller of said PCI variety and would like to know if it will work with my plain-jane non-server desktop board.

[ev0|]

wrong, will not work

[Steven]

wrong, will not work

It won't even fit. :p

[darkmark327]

Then why would this:

http://www.znyx.com/products/pdf/ZX370_Datasheet_02_web.pdf

say this:

64 bit /66 MHZ PCI bus connection

Backward compatible with 32 bit, 33 MHz PCI slots

and this:

http://engr.smu.edu/~niranjan/pci.html

say this:

A transparent 64-bit extension of the 32-bit data and address buses is defined, doubling the bus bandwidth and offering forward and backward compatibility of 32-bit and 64-bit PCI Local Bus peripherals. A forward and backward compatible 66 MHz specification is also defined, doubling the bandwidth capabilities of the 33 MHz definition.

and this:

http://www.adaptec.com/worldwide/product/m...SI%2F&type=SCSI

say this:

A 66-MHz bus is capable of operating at 0 to 66 MHz speeds. 33-MHz devices operate at 33 MHz in a 66-MHz bus; likewise 66-MHz devices operate at 33 MHz in a 33-MHz bus.

And this:

http://www.attotech.com/software/files/tec...PCIFC3300TS.pdf

say this:

PCI 2.2 compliant? 64-bit/66 MHz PCI (backward compatible with 32-bit and 33 MHz PCI)

and this:

http://www.qlogic.com/news-events/details/...ails.asp?id=490

say this:

The ISP2100A is specially targeted at SCSI storage and clustering applications and combines a 66 MHz, 64-bit PCI host interface (fully backward-compatible with 33 MHz, 32-bit PCI systems)

and so on

Thanks again guys, I'm sure your expert opinions on the subject are more valid than the above, particularly adaptec's. Sometimes I wonder why I bother asking questions, all I ever get are answers from people who only think they know what they're talking about.

[Hawkeye]

I believe the way that some PCI-X cards are designed, they are backwards compatible with regular PCI slots, but you get reduced speed/bandwidth/size. To take full advantage of it, you will need a motherboard that has 64-bit PCI-X slots.

[barnabas]

curious..... why would you post a question that you already have the answers for? interesting.......if you were curious if it would work still, why ask your question, just go ahead and plug the card in and bootup. if you fry the card, return it to the place you bought it from and give them the information that you found. it just seems rude, or downright mean, to ask the question, let people give their own answers and then shoot them down for trying to help out. just my opinion, but i hope it makes you think first before you continue posting.

:whistle:

barnabas

[darkmark327]

I didn't know the answer, I researched it when the answer that I got did not agree with what I thought the case to be. Knowing that 99% of what people tell you is wrong, I decided not to put my faith in people who didn't even think it would fit, and so I looked it up myself, and was not surprised to find that my original thought was correct.

And I'm normally not rude but it angers me more than anything when people just post without knowing a damn thing about what they're talking about. Erroneous information for the sake of post counts helps no one. That's why I usually would put a disclaimer to the effect of "if you don't know what the hell you're talking about, don't tell me what you think you know." but that usually results in people getting cranky over my rudeness. Well now I can conveniently refer to this whenever I get such whining.

Edited March 26, 2004 by darkmark327

[darkmark327]

I believe the way that some PCI-X cards are designed, they are backwards compatible with regular PCI slots, but you get reduced speed/bandwidth/size. To take full advantage of it, you will need a motherboard that has 64-bit PCI-X slots.

Yeah, I realize I will get reduced performance, I will be using 32-bit/66 MHz at 33 MHz, so the effective bandwidth goes from 266 MB/s to 133. It's 3 hard drives (RAID 0 + Parity) so I don't foresee having fully utilized such bandwidth anyway. The 5-drive version uses 64-bit/66 MHz which makes sense, because then you'd probably break the 266 MB ceiling, especially if you used all raptors.

Also, all PCI-X cards are backwards compatible with PCI, it's part of the specification.