Disk hardware emulation, was Re: Grandfather system RTE6/VM?

From: Jules Richardson <julesrichardsonuk_at_yahoo.co.uk>
Date: Wed Dec 10 05:37:16 2003

On Wed, 2003-12-10 at 01:07, Tony Duell wrote:
> It was suggested that the emulator should contain enough RAM to buffer
> the entire disk image,

That does seem a little over the top to me. Ditto with suggestions for
various ways of condensing the data stream - if the buffer just needs to
be a couple of MB, then that seems fine - 2MB of fast RAM would not be
unreasonable.
 
> which would be loaded and saved to a PC using a
> (bletch!) USB link. I would still rather have a stand-alone unit that
> would fit inside the classic computer in place of the original drive.

I'm with Tony on the USB side of things :-) The maximum cable length
between drive and controller as Tony mentioned the other day is an issue
though, and one I'd mean to ask about a little while ago. I'd assumed
the average length of 10" or so was more due to physical constraits than
electrical ones, but maybe not (I believe IDE has a limit of about 12",
no?)

That does imply that *something* needs to be inside the classic chassis
due to electrical restrictions. That in turn seems to imply that the
whole lot - in an ideal world - needs to fit in a 5.25" half-height bay;
interface electronics and modern drive replacement. Of course most
classics would have more space than this though, but I'd suggest that
for a final interface things at least fit in a 5.25" bay for convenience
of mounting, even if the replacement drive has to lurk somewhere else.

I just had a rethink on my networking suggestion. My main two reasons
for wanting the drive 'images' on a central machine were a) to avoid
wasting drive space, b) to avoid unnecessary cost, and c) to make backup
easier.

Having one drive per classic doesn't help a) at all, but reliable drives
in the order of 1GB or so can be found for free and are likely to keep
running for a good few years yet (at which point I can switch to
whatever capacity is then the freebie of the day. So b) becomes
irrelevant (I'd still much rather use SCSI drives as that's what I have
spares of - I don't keep IDE drives lying around)

Point c) about backup can be rethought. All the interface needs is
*some* way of getting data out of it (and back into it, presumably :)
It doesn't matter what that method is, nor really how fast it is.
Providing I can back up the contents of the drive easily, and swap in
other drive images, I'd be happy. If it takes a day for a backup to run
I don't really care that much (which does open up the possibility of
running that portion of things over a standard serial link)

Ultimate goal would be to keep this simple *and* low cost, preferably
using parts that people might have lying around in the workshop, or can
at least obtain easily.

cheers

Jules
Received on Wed Dec 10 2003 - 05:37:16 GMT