Re: A7000 RAM SIMMs

On Sun, Oct 07, 2007 at 10:59:48PM +0100, Ben Morrow wrote:
> Andrew Ball wrote:
> >Thanks for the information.  Is the A7000+ discernably faster than
> >the A7000?  Do both models include an ATA interface?  What is the
> >capacity limit for a hard disk?
> 
> The A7000+ has a one-channel (two-device) ATA interface. I'm afraid I 
> can't help with the rest...

The A7000+ is clocked at (I think) 48MHz while the A7000 is clocked at
32MHz, so there should be a significant speed difference.  The A7000+ also
has a floating point unit, though I don't know if things in NetBSD are ever
compiled for hard-float, and the EDO RAM might make a small difference.

For the disc interface, in terms of hardware, it's just a few bus buffers so
any restrictions are, in theory, purely with the OS.  RISC OS 4/6 can drive
up to 128GB (this is the limit of LBA28 addressing - RO6 doesn't yet support
LBA48).  The hardware only supports a few PIO modes so it's fairly slow (no
DMA).  RISC OS 3.7 can, in principle, format to the same sizes but the
Filecore E disc format has a map size limitation.  That means you start
getting things like minimum 16MB per file, and it all gets very inefficient
above about 10-20GB.  This won't bother you if you only format a small RISC
OS partition at the start of the disc and then NetBSD for the rest.

There is a small hardware problem on the Risc PC board that causes it to pay
attention to the /IOCS16 line from the hard drive which is long deprecated. 
Some modern drives, notably Hitachi, have stopped generating this signal
which means the motherboard only latches in 8 bits not 16 bits.  I'd assume
the A7000(+) board has the same arrangement, but don't have a schematic to
check.  More details here:
http://groups.google.com/group/comp.sys.acorn.hardware/msg/3d77c5dddd924ab8

> Since you're writing to this list, I'm going to take a giant intuitive
> leap and guess you're trying (or planning to try) to run NetBSD on an
> A7000...

I've just joined this list because I'm interested in running NetBSD on an
Acorn NC, which is almost the same hardware as the A7000.  Since its only
storage is NFS, I don't suppose anyone might have a root image I could
steal?  Or something that'd save me the effort of trying to install NetBSD
from NFS to NFS.

Is there a recommended 'classic' version of NetBSD to install on these
machines?  ISTR reading that Ben Harris had 2.0.2 running on an NC, and the
website seems to suggest 3.0 should work.  But I'm a little wary of trying
new versions for fear they've never been tested on old hardware.

Theo