64Bit PCI ? (Tyan server boards etc)

[John Prophet]

Just noticed yesterday while looking at a Tyan (or was it Microstar?) Quad CPU server type board...noticed a couple of looooong looking PCI slots. Turns out that they are 64bit PCI slots. Further searching seemed to indicate that they are often used for SCSI controllers etc. Has anyone here used 64bit PCI..are there any cards etc that might interest a power home user. Is that only found on multi-cpu boards?

[otheos]

Currently, 32bit 33Mhz PCI bus is limited to 133MB/s bandwidth. While this is for the moment perfectly ok for home use (nothing can saturate 133MB/s on most home PC's), servers definitely require more than that.

64bit 33Mhz (266MB/s) and 64bit 66Mhz (533MB/s) are quite common to server boards. They are mainly used for SCSI adapters and gigabit ethernet.

With current SCSI interfaces at 160MB/s the 133MB/s limit is already a bottleneck (not to mention the upcoming 320MB/s). Imagine a server with 2 raid arrays attouched on a dual bus 160MB/s SCSI card. This easily totals a 320MB/s bandwidth and calls for the 64bit 66Mhz PCI bus.

Since SCSI devices are used concurrently (unlike IDE) this total bandwidth of 320MB/s is frequently saturated in real use!

All major U3W cards (adaptec 29160, LSI53C1010 based cards -like the Tekram U3W/D, and others more server oriented ones) are now using 64bit interface (usually backwards compatible with 32bit when they aim at workstation/small servers market).

Like I said, 64bit PCI is hardly a requirement for home PC's. With high end workstations and servers it is an absolute must. Like other things however, expect to see 64bit PCI (in its current form or a reincarnation) to home PC's in the future.

[daveleau]

Great info otheos. Thanks!

Dave