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Re: Hmm, IDE DMA seems broken with Etch on my PWS433a (Miata MX5).

On Sat, Sep 01, 2007 at 10:51:07AM -0400, Jay Estabrook wrote:
> Sounds like you could try the CPU swap. But I don't know if the caches
> will run at different speeds, though it's be worth the try. If it
> doesn't come up, or comes up flakey, you'll know... ;-}

Yep I think I will try that since I have two axp164ux boards with 600MHz
CPUs (which so far I haven't managed to make milo work with even though
it should), so I will try the cpu swap and see.

> I think the latest kernels' cmd64x driver is new - there was a call
> recently, on this list IIRC, for help testing the new version, as much
> of the IDE support has been totally rewritten, and there are few
> instances of the CMD646 (?) in the wild beside built into several of
> our Alphas...

Well I am trying to apply the workaround from a 2.4.x patch I found into
the 2.6.18 etch kernel and rebuild that (building as I write this).
Other than being slow in PIO mode the system is now quite stable (unlike
with DMA enabled which caused the HD to vanish as soon as a write
crossed the page boundary (so partition table write no problem, mkfs
big problem).

Since only writes are affected, reads will still be full normal DMA
speed, and only writes that cross a page boundary will be affected, so
hopefully very minor performance impact if it works.

> > My solutions was to go through the installer to just before the
> > partition tool where networking is setup, return to the menu, load
> > additional installer features, and install the ssh client.  I then scp'd
> > the hdparm binary (from the hdparm udeb I extracted on another machine),
> > and ran it to disable dma on the hd.  After that the install when just
> > fine.  I then chroot'd to /target, and installed hdparm and configured
> > /etc/hdparm.conf to disable dma on the hd on boot.  System boots fine
> > with no errors now.
> Clever... :-)

Well after ide=nodma didn't work, I didn't see much other choice (other
than cross compile a "fixed" kernel and regenerate installer, which
seemed like a lot of work).

> > I guess the early miatas require a modified kernel
> > to fix the DMA bug in the cmd64x driver.  I am surprised this has never
> > made it into the kernel yet.  I guess most people run scsi drives on
> > these machines.
> Yes, I believe they were never sold with IDE HDDs, just CDs.

True, but I can't get the stupid scsi drives to show up.  I will
probably buy a new wide scsi cable and terminator and try that, but on
the other hand an 80GB IDE drive is much more useful than a couple of
3.2GB scsi drives.

> If you should decide to try to find a wide SCSI controller, remember
> that SRM doesn't know about Adaptec boards. Best bets are QLogic 1040
> and NCR 875 and prolly 895. I don't know if there are any supported by
> SRM that can do Ultra-3, unfortunately.

Well it has a 1020 board already, other than I can't make the wide
channel work.

I will probably just avoid scsi (too expensive).  I will save my scsi
parts for my sparcs, SGIs and Decstation 5000s instead.  Oh and I
suppose the sun3's might like scsi too (I always ran them diskless with
NFS in the past, but just as Xterms).

Len Sorensen

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