Disk archival techniques

[Randy McLaughlin]

From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
Sent: Wednesday, May 18, 2005 1:48 PM


> On Wed, 2005-05-18 at 12:29 -0500, Randy McLaughlin wrote:
>> From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
>> Sent: Wednesday, May 18, 2005 9:00 AM
<snip>
>> For ROM images just a binary (or hex) file is sufficient since there is 
>> no
>> formatting involved.
>>
>> The only information needed would be a description of what the heck it 
>> is.
>>
>> If we were smart (a long stretch)
>
> ;)
>
> Description's one thing, date would be another, plus checksum info I
> suppose. Plus for these kinds of things it probably makes sense to store
> the name of the person who created the image, and the tool they used to
> do so (can be handy to have the latter for times when a release of a
> tool is found to be broken)
>
> Plus one ROM archive might be intended to be spread across several
> physical chips in some way. I've certainly got ROM images saved from 32-
> bit machines where four physical 8-bit chips are accessed in parallel.
> For the native machine they're accessed that way; for browsing in a hex
> editor or maybe use with an emulator, it'd be handy to have them as a
> linear sequence of bytes. Maybe for that reason some essence of the data
> organisation also needs to be captured in the image archive...
>
> This is just off the top of my head; there may be other things, or
> some/all of these might be wrong. But it does seem to suggest that there
> might be more useful stuff to capture in a ROM image file than just a
> chunk of raw data and a freeform description...
>
>> Papertapes generally come in two flavors:  Text or binary, please note 
>> hex
>> tapes are text files.  The leading and trailing nulls should be stripped 
>> but
>> the data should be kept the same i.e hex tapes should stay hex and not
>> converted to binary.  I have seen people store hex data as binary which
>> strips load address data plus with Intel hex it is possible to load
>> different segments which gets lost when converted to binary.
>
> Sure - I'm no expert at all on tapes! Possibly there are other things
> that'd be usefully captured in a suite of image formats one day - PAL
> chips maybe, or even documentation scans. It's not reinventing the wheel
> if it actually adds useful stuff over and above what's currently
> available of course :-)
>
> cheers
>
> Jules

Multi-part ROM's can be backed up as either the whole or as pieces as long 
as it is documented.  The tools used to extract the data doesn't sound 
important to me.

On many early boards bipolar PROM were used as PAL's.  All programmable 
devices data should be backed up when possible.

Using one manufacturer as an example - Cromemco used bipolar PROMs and made 
their own numbers - 749XX.  This makes it confusing but easy to spot when 
seen.  They would use the chips on multiple boards keeping the same 
programming by chipnumber i.e. 74901 could be used on a floppy controller or 
memory card and still be interchangeable (I just made up an example but I've 
seen common 749XX across different types of cards).


Randy
www.s100-manuals.com