Subject: Re: NetBSD/i386 and single board computers
To: None <port-i386@NetBSD.ORG>
From: Greg A. Woods <email@example.com>
Date: 12/05/1997 21:03:23
[ On Thu, December 4, 1997 at 22:28:32 (GMT), Matthias Drochner wrote: ]
> Subject: Re: NetBSD/i386 and single board computers
> When I tried a backplane with 16 PCI slots (4 PCI-PCI bridges)
> it was a complete disaster: No 1 slot was properly configured
> by any of the CPU boards. Obviously the backplane uses
> an IDSEL routing which the CPUs don't expect.
> BIOSes are generally a weakness: They are generic PC
> BIOSes, not well suited for embedded use. (One exception:
> A Teknor CPU could be partly managed over a serial line.)
> It's a bad joke to have an AMI WinBIOS on an "industrial"
Good to hear about that Teknor board -- that's one of the ones I've been
looking at. Have you worked with any of their CompactPCI boards yet?
Note that many of those "industrial" systems are now looking like
embedded flat-panel systems which can be programmed just like PCs, so
having a home-PC style bios on them isn't too surprising....
> I've got 2 CompactPCI systems too. I suspect the PCI
> bus to be electrically unstable, at least I'm experiencing
> random hangs if a device does DMA. The logic analyzer shows
> that the device properly asserts the bus REQ, but never gets
> a GRANT.
> The Intel PCI chipsets can only drive 4 PCI masters,
That's not surprising if you look at the PCI design spec. It's amazing
that it works with 4 boards at all, which is why I suspect that many PC
motherboards only have two or three PCI slots -- they just can't design
in enough quality to make any more slots work reliably. (4 is the max
of the design. period. which is why your 16-slot had 4 bridges, and
that's the total max expandability I think, unless you cascade bridges)
I think in the end the VME320 stuff will be much more reliable and give
similar performance, but for now it's very proprietary.
> I'd probably trust the FORCE boards a bit more, but they
> refused to sell me one without enclosure, disk and NT
That sucks. I can probably get those boards on their own through a
> I never had this amount of trouble when I worked
> with VME boards. But they never had an 80x68, an
> ISA bus nor a PC BIOS...
I may try getting my hands on a a Pentium on VME64X implementation....
The industrial Dec Alpha's are just too expensive, and most everything
else would require more work to get netbsd running on than I can afford
to spend right now.
Greg A. Woods
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