Re: What to do with slow Chip/ST RAM

["David Brownlee" <abs%absd.org@localhost>]

From:  <mlelstv%serpens.de@localhost>

> >Uhm... what's exactly the purpose, again? If it is for prioritized
> >used of main system RAM, I think ZII RAM (at least) isn't accessible
> >to (at least some of) the SCSI DMA drivers.
> 
> Au contraire. Z-II RAM is, Z-III RAM and other 32bit RAM on accelerator
> boards isn't. But this depends on the SCSI controller, in particular
> if it is itself sitting on the Z-II bus.
> 
> That's why AmigaOS (finally) also kept track of MEMF_24BITDMA.
> 
> All this is pretty academic though. Most people will have an
> accelerator with local RAM and local SCSI controller, or an
> A3000 with a SCSI controller that has no such limitation, or
> an IDE adapter run in PIO mode.

Does NetBSD at least warn about such a problem SCSI controller?

From my perspective RAM is split into
a) ram not suitable for running programs, some of which may need to be reserved 
for device DMA (depending on the type), the rest should be exposed as via 
altmem so it can be used as swap or ramdisk
b) general purpose ram, which should be sorted by relative speed so the system 
can always use faster ram first