Riccardo Mottola wrote:
> on 6/7/04 2:09 PM, Tim & Alethea Larson at thelarsons3@cox.net wrote:
> 
> 
>>You want a Quadra, basically.  Fastest 68040 chips in Macs were 33MHz
>>(630, 650, 800, 950 models) or 40MHz (840AV).  I've heard that the SCSI
>>driver that NetBSD uses on the AV models is not as well developed
> 
> up to 1.6.2 it is still true...

I've sent in preliminary DMA support for the AV's in the form of a PR. 
However, the performance still isn't great because while the data gets 
moved with the DMA engine instead of the CPU, the NCR SCSI chip doesn't 
ship much data because it's stuck in asyc transfer mode. Some work needs 
to happen to get synchronous transfers to work. If synchronous transfers 
worked, I have no doubt that DMA transfers would be quite fast, even in 
their preliminary state. Furhter optimizations could happen on the DMA 
transfers after that but they are window dressing compared to getting 
sync transfers to work.

-- 
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  Michael Zucca - mrz5149@acm.org
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  "I'm too old to use Emacs." -- Rod MacDonald
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