HxC emulator documented for Cromemco Users

[marcus bennett]

Dear All,

So I got the time to document my installation of the HxC diskette emulator here

http://majzel.blogspot.com/2014/04/the-hxc-solid-state-diskette-emulator.html

Just to repeat ... I now have a single HxC unit that sits there in the Z2 which presents both

A: and C: to the computer.

(I can't tell you how many of those annoying Gotek or similar 100 floppy emulators I bought, all

a great waste of time and money)

Actually either disk could be 5.25" or 8" because (for example) the RPM  speed is stored in

the virtual diskette image file (.HFE) on the SD card.

But to avoid confusion the best I could come up with is

CDOS

CROMIX

sees:

Drive A = HxC drive A,  NORMALLY 5.25"
Drive B = Physical 3.5" emulating 8"
Drive C = HxC drive B, NORMALLY 8"
Drive D = Physical 5.25"

I had an issue configuring HxC as a Cromemco D: drive and the manual(s) did not help me

so I gave up.

As configured with Cromix loaded you might refer to  sfda, usfda and fdc, ufdc devices

as the mapped SD card emulated drives mapped to individual .HFE files.

Exceptionally you might have an old CDOS that can only boot to the A: and so in that case you 

could have the appropriate 8" image loaded to the A: of the HxC and it will still boot,

it is just my convention that tries always to have the A: as a small disk and the C: (fdc) disk as large.

I also wrote a separate article about the many different use case tests I am (still) making

So in about 1 week I'll post that when all the cases are tested.

Regards Marcus.

[Michael George Hart]

Thank you Marcus,

This information is going to be extremely useful for keeping all my old systems alive

Especially me trying to make use of my complete set of CS 250 boards 

Thanks

Sent from my iPad

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[bah]

Hi Marcus,

  Thanks for all the stuff about HxC.  I have had one for some time and never tried all the configurations you did.  I was mostly using it to archive all my old disks by using COPYDISK from a real disk drive to the HxC.
  I downloaded and tried your HFE files on the C-10 and came up with these results:

SMSSSDST  worked   81kb
SMSSDDST  worked 188kb
SMDSDDST  worked 386kB
SMDSSDST  worked 171kB

CSDSDDST  didn't work with error message "Drive B cannot read CROMIX diskettes"

All the others did not work with either Home Error or Seek Error.

I was not surprised that most did not work because of the weird C-10 hardware.  Though I was glad that all the double/single sided and double/single density configurations for the small disk (5.25") worked flawlessly, even though the C-10 cannot format in 3 of these formats (only DSDD)

It was disappointing that the 8" HFE's did not work as I was hoping that would be a good way to increase the drive capacity of the C-10 without having to have a physical drive.  In the SUDS it mentioned that the CDOS 3.07 can handle 8" drives and there was a real drive that was supposedly sold for the C-10, though I have never seen one.  It might be that the sector layout for 8" is different for the C-10 than for other Cromemco boxes - though I thought 8" was a standard format unlike the 5.25" of which there are hundreds.  That different errors occur (HOME and SEEK) suggests there maybe some subtle difference.  When HxC updates to allow changing the track configuration (or at least the first track in Cromemco's case), I might be able to manually create a blank that works.  Also I could get back into IDA to decompile the 32kB ROM code for the disk access and see if there is a weird skew table for 8" disks.

Thanks for all the time.
Ciao
Brett

[Marcus Bennett]

Brett,

I working at a disadvantage of never having seen/ used a C10.  But can you enlighten me, and perhaps the many ...

CDOS .. the last version I ever saw wa 02.58 and so your version 03.07 is curious.  Not that I am doubting you but can you provide some screenshots.  I tried to boot a C10 diskette on a Z2 and not surprisingly it does not work.

next, for your C10 code ... is there a CDOSgen program as for regular CDOS.  For regular cdos this is where you specify what drives have what sizes and densities.  I will post a printout here when I get the chance.

regards marcus b.

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marcus bennett    amo...@gmail.com majzel.blogspot.com

[bah]

Hi Marcus,
   Yes it is a bit of a weird thing Cromemco did.  Basically the initial C-10 had CDOS on disk, and was version 2.X. The C-10 had a 16kB ROM which contained the CROS (a resident system that allowed connection to a serial port, read/write memory, read/write tracks, tests, etc), but the actual CDOS was on a disk as cdos.com. The last version was 2.65.  This may have only been for the C-10.  One of the things that annoyed me as a kid using it was there was no CDOSGEN program, unlike all the literature from Cromemco said about their other systems.  In June 1984 they released SUDS 5, which was a new ROM that contained the whole CDOS in ROM (32kB).(you had to jumper the motherboard as well)  This version was 3.07.  The cdos.com file was removed from the floppy disks (as it was not necessary now).  There were no versions after this.  I think it was Cromemco's last hurray for the C-10 as CP/M and Z80 were old by then and the new 16-bits were overtaking everything.  The great thing about them putting it it ROM was that you got to use 53kB of memory instead of the 40kB-ish in previous 2.65 and earlier versions.  This was great for me as a Turbo Pascal user.  In version 3.07 they also mentioned it can now run 8" floppy disks (the CLD), and that CDOS automatically determines the type of each drive the first time it is accessed.
They also fixed up some CP/M calls, such as 31 that allowed as they said "CDOS is now as fully CP/M-compatiable as possible".  Of course this was not the case, and my brother and I wrote a CDOS overlay using the feature of remapping the beginning of CDOS to a lower memory address.  This allowed us to intercept certain incompatiable calls and regigged them to be the same as CP/M.  If I remember the only issue we still had was that some address in the lower 100H memory area that the C-10 used for an interrupt whereas CP/M wanted it as a BIOS jump location, or some such.

I have attached picture of C-10 (and closeup of the CDOS version).  I will scan in the SUDS release notes as it contains lots of other information about the change.
Thanks
Brett