OT: Is PCI-X the same as PCI-E?

  • Thread starter Thread starter Lady Margaret Thatcher
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Lady Margaret Thatcher

I know this is a noob question, and I'm not a newbie in general, but
hey, lots going on.

That is, if I have an LSI 64- bit PCI-X SCSI controller, can it go
into a PCI-E system? At what speeds?
 
Lady Margaret Thatcher said:
I know this is a noob question, and I'm not a newbie in general, but
hey, lots going on.

That is, if I have an LSI 64- bit PCI-X SCSI controller, can it go
into a PCI-E system? At what speeds?
Click to expand...

That depends. For example the Asus A8N-E has the following PCI-x slots:

1 - PCI-x16
2 - PCI-x1
1 - PCI-x4

The PCI-x4 slot on the Asus supports PCI-x1, PCI-x4, PCI-x8, or PCI-x16
cards at speeds up to 1GB/sec

These are in addition to the 3 standard PCI slots. The PCI-x16 is normally
used for a video card, but you can put a video card in the other PCIx or PCI
slots, assuming they fit into the slot.

So you need to determine what size slot your SCSI card needs.
 
Mark A said:
That depends. For example the Asus A8N-E has the following PCI-x slots:

1 - PCI-x16
2 - PCI-x1
1 - PCI-x4

The PCI-x4 slot on the Asus supports PCI-x1, PCI-x4, PCI-x8, or PCI-x16
cards at speeds up to 1GB/sec

These are in addition to the 3 standard PCI slots. The PCI-x16 is normally
used for a video card, but you can put a video card in the other PCIx or
PCI slots, assuming they fit into the slot.

So you need to determine what size slot your SCSI card needs.
Click to expand...

Actually, I am not sure it supports 64 bit PCI-x. I would check with Asus or
the SCSI card manufacturer for clarification.
 
I know this is a noob question, and I'm not a newbie in general, but
hey, lots going on.

That is, if I have an LSI 64- bit PCI-X SCSI controller, can it go
into a PCI-E system? At what speeds?
Click to expand...

They are completely different bus standards. PCI-X is a parallel
data bus. It is related to the slower original PCI bus, only is
wider and clocked faster.

PCI Express is a serial protocol, and is point to point. The wires
between a PCI Express slot and the chipset, are for the exclusive
use of that slot alone. The advantage of a point to point interconnect,
is there is no interference from one card, on the operation of another,
at least from an electrical interconnect signal quality perspective.
The signals used are low amplitude, differential, and are incompatible
with the higher amplitude single-ended signals on a PCI parallel bus.

http://www1.us.dell.com/content/topics/global.aspx/vectors/en/2004_pciexpress?c=us&l=en&s=corp

This doc says your controller card should fit in a standard 32 bit
PCI slot, as well as a 64 bit slot. Perhaps that is worth a try
(just to see if the PCI 32 bit slots on most PCI Express boards,
offer a potential home for your controller). In any case, the
mechanical details should prevent incompatible hardware from being
plugged together.

http://www.bellmicro.com/fibrechannel/newasp/lsi_hba/downloads/sym21040.pdf

If you are moving to a PCI Express motherboard, either search for a
PCI Express disk controller, or see whether your current card will
fit into a standard 32 bit 33MHz PCI slot, as they are typically
still used on PCI Express motherboards. I believe there are controllers
that will fit in either a 32 bit or a 64 bit slot, so if the 21040
doesn't work out, there may be some other old controller that will.

Paul
 
I know this is a noob question, and I'm not a newbie in general, but
hey, lots going on.
That is, if I have an LSI 64- bit PCI-X SCSI controller, can it go
into a PCI-E system? At what speeds?
Click to expand...

PCI-X cards do not work in PCI-E (Express) slots. You can
install many 64-bit PCI-X SCSI cards in a regular 32-bit
PCI slot but the transfer speed to the card would be halved
That doesn't mean hard drive performance would be halved
since no drive has a high enough sustained transfer rate.
 
KC said:
You can
install many 64-bit PCI-X SCSI cards in a regular 32-bit
PCI slot but the transfer speed to the card would be halved
Click to expand...

Actually PCI-X has 4, 6 or even 8 times the bandwidth of standard 32-bit
33 MHz PCI, at 66, 100 and 133 MHz, respectively. PCI32/33 is fast
enough for the STR of a single current 15k SCSI drive but turns into a
bottleneck as soon as two or more drives are involved. Besides, not all
PCI-X cards that work in PCI32/33 slots perform well there. An U320 HA
would be total overkill there, U160 (even the 33-MHz LSI 53C1010) would
be plenty good enough. A HA like the OP has would obviously be much
happier on a board that actually features PCI-X slots, typically
workstation-class stuff.

Stephan
 
They are NOT compatible. PCI-X is a rarely seen standard used in some
high-end Workstations; not used in consumer machines. PCI-Express is
currently used in the latest consumer oriented motherboards.
 
Not true although it may seem that way.

While you may not be able to buy many PCI-e devices at the moment, it is
intended to take over both PCI (all variants) and AGP.

Examples of current PCI-e devices include network and high end RAID / SCSI /
SATA controllers. I believe Creative has a sound card out also (see, there
isn't much, it is all hear-say).
 
Tim said:
Examples of current PCI-e devices include network and high end RAID / SCSI /
SATA controllers. I believe Creative has a sound card out also (see, there
isn't much, it is all hear-say).
Click to expand...

No Creative PCIe sound cards are to be expected in the near feature -
one article I read said they encountered performance problems with the
bus (optimized for high bandwidth, but not very efficient for
low-bandwidth devices) and have to work on the interface some more.

Stephan
 
Actually PCI-X has 4, 6 or even 8 times the bandwidth of standard 32-bit
33 MHz PCI, at 66, 100 and 133 MHz, respectively. PCI32/33 is fast
enough for the STR of a single current 15k SCSI drive but turns into a
bottleneck as soon as two or more drives are involved. Besides, not all
PCI-X cards that work in PCI32/33 slots perform well there. An U320 HA
would be total overkill there, U160 (even the 33-MHz LSI 53C1010) would
Click to expand...

Yeah, I know it is overkill, but I got a helluva deal on ebay.
be plenty good enough. A HA like the OP has would obviously be much
happier on a board that actually features PCI-X slots, typically
workstation-class stuff.
Click to expand...

The tail shouldn't wag the dog, but when I upgrade next, I'll look
into "workstation" class motherboards, especially since I am going to
start doing a lot with Photoshop

--thatcher--
 
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