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Re: nbd vs. failing HDDs (was Re: Status)

On Thu, 8 Sep 2011, Brad Boyer wrote:

> On Wed, Sep 07, 2011 at 01:58:56PM +0200, Ingo J?rgensmann wrote:

> > 
> > But yes, on Macs SCSI was always slow, afair... ;-)
> I still haven't found the time to get it working in Linux, but I did 
> find and buy a 100BaseT NuBus card. It even has a chip on it that 
> appears to be the same one as in some cards that are supported on x86, 
> so it might even be relatively simple.

I have one of those cards too but there are more important things to work 
on first.

> I don't expect to actually get close to 100Mb/s out of it since NuBus 
> only runs at either 10 or 20MHz, but it should beat out the 10BaseT 
> cards.

Which machines have 10 MHz NuBus, BTW?

> The SCSI performance on a Mac depends a lot on the hardware. My IIfx was 
> so slow that I think I let it run for two days doing a dist-upgrade of a 
> minimal install. The disks do something in the 100kB/s range as I 
> recall. Most other Macs are much better.

Not exactly. Here's the situation:

NCR5380 chip in PIO mode (as used on IIfx): slow (at best)
NCR5380 chip in PDMA mode (other early Macs): broken
DP53C9X chip in PIO mode (as used on 660av & 840av): stable but slow
DP53C9X chip in PDMA mode (other Quadras etc): stable and fast

The web site has some info about the individual Mac models:


> I recently acquired an FWB JackHammer card, which can take 68-pin
> SCSI drives. It uses an NCR 53c720, so it should be possible to
> get it working and get much better SCSI performance than the
> built-in SCSI interfaces of any Mac (including ppc models).
> 	Brad Boyer
> 	flar@allandria.com

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