Messages in this thread | | | Subject | Re: ServerWorks LE and MTRR | From | (Eric W. Biederman) | Date | 30 Apr 2001 02:55:26 -0600 |
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Steffen Persvold <sp@scali.no> writes:
> nick@snowman.net wrote: > > On Sun, 29 Apr 2001, Steffen Persvold wrote: > > > > > I've learned it the hard way, I have two types : Compaq DL360 (rev 5) and a > > > Tyan S2510 (rev 6). On the compaq machine I constantly get data corruption > on > > > > the last double word (4 bytes) in a 64 byte PCI burst when I use write > > > combining on the CPU. On the Tyan however the transfer is always ok. > > > > > > > Are you sure that is not due to board design differences? > > No I can't be 100% certain that the layout of the board isn't the reason since > I haven't asked ServerWorks about this and it doesn't say anything in their > docs (yes my company has the NDA, so I shouldn't get to much in detail here), > but if this was the case it would be totally wrong to disable write combining > on any LE chipset. > > The test case that I have been using to trigger this is sort of special because > we are using SCI shared memory adapters to write (with PIO) into remote nodes > memory, and the bandwidth tends to get quite high (approx 170 MByte/sec on LE > with write combining). I've been able to run this case on 5 different > motherboards using the LE and HE-SL ServerWorks chipsets, but only two of them > are LE (the DL360 and the S2510). Everything works fine with write-combining on > every motherboard except the DL360 (which has rev 5). > > One basic test case that I haven't tried, could be to enable write-combining on > your PCI graphics adapter memory and see if the X display gets screwed up. > > I will try to get some information from ServerWorks about this problem, but I'm > not sure if ServerWorks would be happy if I told you the answer (because of the > NDA).
I'd like to put my small plug in that this make me a little nervous. It could also be a problem with the firmware (aka BIOS) missetting something up. Working with linuxBIOS I have seen burst-writes (enabled with write-combining or write-back) cause data corruption when non-burst-writes to memory don't cause problems, when the memory controller is setup wrong. (This is was with intel 440GX & 440BX chipsets).
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