Re: suggestion on initial IDE-boot configuration

[Rick Thomas <rbthomas55@pobox.com>]

Interesting... I don't think it's unique to Sparc machines.

I've encountered the same problem with a "RevA" Blue&White Macintosh G3.

It looks as though the problem is that the card is capable of 
faster performance than the PCI bus can sustain.  The card 
advertises it's highest performance level, and the kernel attempts 
to use it, but the poor old PCI-bus has trouble keeping up.   I 
don't know enough about the hardware protocols involved to tell, 
but I would think that there ought to be some way of finding out 
what the PCI bus is (or claims to be) capable of, and taking that 
into account when deciding which DMA mode to use.  Failing that, 
there ought to be some kind of automatic fall-back to a slower mode 
if you get more than a few "missed interrupt" indications.

Rick



On Tuesday, September 21, 2004, at 09:05 PM, Steve Pacenka wrote:

> On Tue, 2004-09-21 at 07:23, Jurzitza, Dieter wrote:
> > Dear listmembers,
> > my experiences with my U60 lead me to the following suggestion:
> >
> > -> put a default "ide=nodma" as kernel parameter on SPARC
> > -> make the user / the configuration enable dma via /etc/init.d/XXX
> >
> > why?
> > U60 cannot cope with udma-modes (AFAIK, on those Promise 
> > controllers I have tested) > 2. If you i.e. use an external 
> > controller that enables max-dma-speed by default, the 
> > installation will always fail - assuming you want to install on 
> > an ide-hdd.
> > If this would be an installation option (maybe with a 
> > test-structure ...) IMHO ide-installation could run smoothly.
> > Somebody who does not know about the potential problems will 
> > never be lucky with this. Any hdd-setup will fail due to the too 
> > high speed drive-access due to the dma-mode.
> > Take care
>
> Two questions:
>
> 1. Would this have side effects on built-in IDE controllers in Ultra 5
> and 10?  I didn't need to do anything special when installing or 
> running
> Sarge on these.  My U10 at work runs very reliably at a default mdma2,
> with a Seagate 80G drive capable of ATA100 (udma4?).
>
> 2. Doesn't the disabling of DMA make throughput really lousy?  How 
> about
> a USB2 or firewire card and an external drivebox, if one must use IDE
> drives?