ImageDisk and some 8" images posted

Dave Dunfield dave04a at
Wed Aug 3 04:57:58 CDT 2005

Hi Fred,

>Q: are you going to continue to expand the collection of images,
>and perhaps take over where Don Maslin left off?
>If so, read through to the end!

I am actively attempting to archive all of the system disks in my collection.
My primary purpose is to preserve them so that I will not lose the data should
the physical media go bad - however I see no reason not to make them available
should other people need these disks.

If others want to contribute images to the archive, I will certainly welcome
them - or if someone else wants to set up a repository of images, you are welcome
to take the ones that I have done.

>> One weakness - the program currently cannot handle disks which have different
>> sector sizes within the same track ... so far I have encountered only one disk
>> type which *MAY* do this, BMC if800 - TeleDisk reports that the sector size
>> changes within the track ... however I have never been able to get TeleDisk to
>> restore a workable disk, so I am not convinced that it handles it either - it
>> also reports sectors missing and "no data" in sectors, as well as really odd
>> sector numbers - I have a feeling that it is an incompatible format and it is
>> getting "garbage". Still, it's an option I could provide if there proves to be
>> a need.
>IIRC, the Ensoniq Mirage had mixed sector sizes.
>There is apparently at least one BMC if800 format that can be done with

I looked into this a bit more after posting last night, and it looks like
the 765 cannot do mixed sector sizes ... Although you do feed it the sector
size for each sector, it also requires the sector size as one of the initial
command parameters - I'm guessing the initial parm sets the actual sector
size formatted, and the DMA value simply controls what gets written to the
ID fields :-(

>I had some difficulties with "automatic format recognition", particularly
>from used reformatted disks.  I wasted some time when somebody sent me
>single sided disks that had been formatted over PC 360K disks, which
>hadn't removed the old content on the second side, and with HP 3.5"
>diskettes that only rewrote the first 77 tracks, etc.

I've run into these issues as well - ImageDisk will analyze the disk for you
if you don't know the format, however it also allows you to manually set many
of the parameters. For example, when I know that a system is single-sided, I
usually tell ImageDisk to only do one side.

>Because I was only dealing with file transfer, I never bothered to even
>list which of the sample format diskettes that I have are system disks.
>Would you like me to send you some sample diskettes to look through?

Thanks - I'll may ask for some, but at this point, I believe most of the
incompatibilities I am encountering are due to limitations of the 765. Once
we have a bit more experience and information with ImageDisk, I may take
you up on the offer for some specific formats.

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools:
com             Collector of vintage computing equipment:

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