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64bit pci / pcix question

E

Exocet956

[H]ard|Gawd
Joined
Jan 25, 2001
Messages
1,387
I’m confused as to the differences between pci and pci X what is the difference between 32bit and 64 bit pci and pci X. 32bit 33mhz is 133mbs for the entire bus. 32bit 66mhz is 266mbs for the entire bus. What are the different pci speeds? Is there a difference between 64bit pci and pci X?

I’m basically looking for a break down of the different types of pci and their corresponding speeds and available bandwidth. any info or links will be appreciated.
 
http://www.pcisig.com/

Conventional PCI can be 32 or 64 bit, at 33 or 66 MHz. All four combinations are possible, though the most common by far is 32/33.

PCI-X (eXtended) is 64-bit, and can be 33, 66, 100, or 133 MHz. PCI cards will work in PCI-X slots, but PCI-X cards will not work in PCI slots.

Bandwidth of PCI bus is: (bits X MHz)/8, so (32x33)/8 = 133MB/s. Use that formula for all combinations above to find their max. bandwidth.

PCI-E (Express) is a whole other story.
 
sm8000 said:
.....but PCI-X cards will not work in PCI slots.
Click to expand...
Absolutely, positively, not true. PCI / PCI-X cards and slots are supposed to be fully compatible with each other. It is true the the bus / card combination will run at the "lowest common denominator" (meaning, the slowest card or slot on the bus defines the bus speed and protocol) but they can and do work interchangably.

The 64 bit 133 MHz PCI-X products I work with are tested in 32 bit 33 MHz PCI slots as a matter of course when being qualified.

Rock on - B.B.S.
 
What is the formula for pci xpress? the reason why I’m asking is im debating on which bus I’m going to go with for my next fileserver motherboard. I already have 32bit 66 mhz pci cards I want to use. I realize pci express is the future but all the pci express boards I have seen only have standard pci slots as legacy slots. isn't the vast majority of integrated componets still on the pci bus? I.e. sound, firewire controllers, raid controllers etc. I know most gigabit controllers have been moved to pci express because of the bandwidth requirements.
 
At the current time I would easily stick with PCI-X over going with with PCI-E. PCI-X has an established base and a lot of options. I'm not even sure I've even seen ANY PCI-E cards, except video cards.

A PCI-X/133 card moves 1066MB/s so I would assume it's more than enough for whatever you're doing.

Just don't put any standard PCI cards into PCI-X slots or you'll slowdown the whole bus.

-MrD
 
For a file server, PCI-X is the route you want to go. PCI Express (x16) might have more bandwidth than PCI-X, but not by much, and to no effect on file server performance. I would venture to guess that most file server operators go for the long haul, making investments on expensive controller cards that will last. This makes the very compatible PCI-X platform much more attractive. That, and all of the serious controller ASIC and controller card manufacturers all have PCI-X products already.
 
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