[Intel-devsys] IMAGEDISK for MDS 8" SSSD disks

Herb Johnson hjohnson at retrotechnology.com
Fri Feb 21 21:17:18 MST 2020

Roger asked if anyone is home: I'm listening but got busy. I will submit 
suggestions to show the lights are on, even I'm not "home" to give a 
good solution.

So, can someone send Roger a disk formatted SSSD on a 225's controller? 
So he can read it on his PC/AHA/Imagedsk system and look at the details 
of the track and sector formatting? and the sector interleave?

Or of course - if Roger can write such a disk on his 225, and it works 
on his 225, then he can try to read it on the PC to see its format. My 
recollection is that my CP/M system programs (DU) can at least read 
sectors on an ISIS diskette - of course it can't recognize the ISIS disk 
as a CP/M disk for obvious reasons.

Seems to me, if the PHYSICAL interleave between sectors is wrong, even 
if the bit-format is right, the MDS may run out of time between sector 
reads, and not be able to process the diskette.

It gets confusing to read off sectors of real disks, and determine what 
a "physical interleave" is. one may have to do a "track read" and then 
parse the track as read, read off bits and so on. Ancient PC programs 
like "ANADISK" I think provided such capability.

The other possibility of fault? Writing the imagedisk image too 
literally on the PC. Say the imagedsk image is physical-sequential 
sectors. Maybe the PC imagedsk is writing out the image as sequential 
sectors - when it should not, they have to be interleaved.

Roger's setup is the one to be verified, so 1) confirm his MDS is 
working with 'proper' SSSD Intel-format disks and 2) his MDS can process 
such disks OK - then he's testing against a known-good result and merely 
needs to 3) REPLICATE the known-working Intel diskette format on his PC 
setup, down to all the bits and sectors in the right, physical, places.

Hope that's helpful.

Regards, Herb Johnson

On 2/20/2020 10:06 PM, Roger Arrick wrote:
> Happy 2020 MDS crew!
> I need some help - It concerns SSSD formats on 8" disks MDS225.
> My latest project is to build an IMAGEDISK system on my PC to write .IMD
> files for various machines like Altos and Xerox 820.
> I have the adaptec AHA-1542CF controller which can do SD on a PC.
> I've succeeded in writing SSSD 5.25" disks for my FLEX9 SWTPC system.
> So lots of things are working.
> Now I have an SA800 8" drive going through a DBIT adapter which 
> generates the T43 write comp signal.
> I can read a standard CPM disk (SSSD, 28 sectors, 128 byte sectors, 77 
> tracks).
> This CPM disk will also read in my MDS225 running CPM using the systems 
> SD integrated drive.
> But the disk I write out of imagedisk, which is a copy of this CPM disk, 
> will NOT read in my MDS.
> I can view this disk on the PC using IMDV and can see the CPM directory 
> but I can see that some of the interleaves are different.
> So, what would stop the MDS from reading an apparently good CPM disk.
> IMD has a setting for R/W gap and Format gap.
> I've tinkered with these a bit but no success.
> Any ideas?
> _______________________________________________
> Roger Arrick
> Roger at Arrick.com
> Tyler, TX
> _______________________________________________
> Intel-devsys mailing list
> Intel-devsys at lists.brouhaha.com
> http://lists.brouhaha.com/mailman/listinfo/intel-devsys

Herbert R. Johnson, New Jersey in the USA
http://www.retrotechnology.com OR .net
preserve, recover, restore 1970's computing
email: hjohnson AT retrotechnology DOT com
or try later herbjohnson AT retrotechnology DOT info

More information about the Intel-devsys mailing list