Compact-PCI format motherboards?

[cheesehead]

Having seen many deals on compact-PCI and PICMG format single-board-computers, I wanted to know how they work. Considering that two 600mhz SBCs and a backplane can be had for under 100$, it would seem that they would be an interesting way to make a cheap server. (After all, with twelve PCI slots, why not just use a bunch of cheap NICs and a SATA card for storage?)

 

[Peter]

CompactPCI x86 single board computers (at least those we make) are just your ordinary PC, with lots of features crammed onto the main board. The backplane is a PCI expansion bus; so if you want to plug two SBCs, one of them will have to be capable to run as a peripheral board, not a system CPU. This will not be a dual-CPU system then, but two systems running in one chassis - one "owning" the expansion backplane, the other being isolated from it.

If you're buying those used, take care that you get the "rear I/O module" boards as well. This is where most of the usual I/O ports are, and if you don't have it, you won't get far.

CompactPCI slots are electrically PCI, but they're mechanically quite different.

PICMG are computer-in-a-slot that takes you straight to standard PCI and ISA slots, desktop form factor. It's just a modular approach to building a non-rugged computer. Here, you get to use your ordinary PCI cards.

 

[interchange]

I work with Compact-PCI embedded systems daily. I do board support software for airplane computers. I'm not really sure where CompactPCI is being used, but it's very useful to us as backplane communication between boards is often a necessity, and something better than, say, ethernet is a requirement .

 

[Peter]

Sure, if the SBCs run as peripherals, you can use their bus interface bridge chips as a physical layer for network connections, running either peer-to-peer access into other peripheral SBCs, or using a shared memory location in the system host's RAM.

Incidentally, my uni thesis was on shared-memory network transport, eleven years ago. Man I'm old