PCI-X Compatibility

[u9dbg]

I am looking at purchasing a new Mobo, which has PCI-X ports on it 1 at 133Mhz and 3 at 66 Mhz, anyone know if these are backward compatable with standard PCI?

I have read that PCI-X is backward compatable and that PCI-Express isnt, however until I read that articale I thought that PCI-X and an abrevation of PCI-eXpress???

Anyone up on the new hardware care to shed some light on this.

Also anyone know if you can plug a Xeon CPU in to a standard P4 Mobo?


Thanks

David

[BipolarBill]

A Xeon is a socket 603 product. It won't fit in a socket 478.

The plan is to provide PCI "legacy" ports in new PCI-X motherboards. A PCI-X bus can indeed provide Legacy PCI ports if the motherboard maker chooses to include them. It seems to me that you need to check with the board maker or simply find an image of it.

I believe that PCI Express is a chipset feature rather than an an entire system bus. I also believe that it is used with the new Athlon 64 for the memory interface.

Maybe Peter M can clarify...



Motherboard question - moved.

[u9dbg]

the board in question is an ASUS PP-DLW 2XSKT604 E7505,

it has 1 standard PCI socket, but I have a current RAID IDE controller and also a SCSI controller which i plan to put in the new server, I cannot afford to upgrade these to PCI-X cards at the mo so I need to know whether you could plug one of the cards in to the 66 or 133 Mhz sockets

[BipolarBill]

Well, I would then wait awhile for a board with the storage controllers you need included. An IDE RAID feature won't be far away. The SCSI adapter is another matter. I would favor that in the PCI slot.

[BipolarBill]

Oh - I see. I have it backwards. PCI Express will be the new system bus:

http://www.intel.com/update/contents/dt10031.htm

PCI-X is just the designation for the enhanced PCI bus for hosting 66MHz/64-bit PCI slots.

Peter would know if you can use a standard PCI card in them, but I do know that this one will work:

http://www.newegg.com/app/viewProductDesc.asp?description=16-118-009&depa=0

It's a very good card and dirt cheap.

[u9dbg]

thats a good point but xeons have been around for a while now, and one wonders why there aint much about that supports it yet, i have found the odd board that supports IDE raid aswell, but they are like £200 more expensive.

Idealy i need to find a board within the next 3 weeks, I have deadlines to meet and servers to migrate :(

[BipolarBill]

Aha! You can use standard PCI cards in the PCI-X slots, but the entire array of PCI slots will be limited then be limited to 32-bit/33MHz.

That's what the manual says.

[Peter M]

PCI-X is still backward compatible, parallel bus technology. PCI Express is serial, point to point, each slot/device its own connection.

PCI-X reaches up to 133 MHz at 64 bit bus width. The more devices on the same bus, the lower the frequency. Over standard PCI at 64-bit/66 MHz, it has the advantage of more effective transfers.
And it's backwards compatible to legacy PCI, both at 66 and 33 MHz. Note that since it's a bus, if you plug a slow device into a fast bus, everything else on the same bus will be forced to use the same slow speed as well.

[u9dbg]

thanks people for clearing that one up, most useful.

So to recap, a Xeon CPU needs a Xeon motherboard and wont go in a standard P4 socket.

PCI-X has legacy pci support but if you use a standard legacy PCI card in a PCI-X socket it reduces the whole bus to standard PCI speed

[BipolarBill]

That's about it.

[Peter M]

So if you want fast I/O without the cost of going Xeon, you should look at Opteron boards, e.g. those from Tyan. There's a nice range of single- and dual-CPU boards with many combinations of PCI, PCI-X and AGP slots.

[u9dbg]

already got 3 xeon chips, a freebie from a supplier, so just the board needed