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Yeah, one of the long-standing boners of the new floppy system is that higher-density drives can't read lower-density disks even though that's entirely possible on real hardware. If that was solved we could just default everything to the highest density drives and the crash wouldn't be a problem. (Although of course the crash should still be fixed).

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rfka01 Offline OP
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Originally Posted By R. Belmont
Yeah, one of the long-standing boners of the new floppy system is that higher-density drives can't read lower-density disks even though that's entirely possible on real hardware. If that was solved we could just default everything to the highest density drives and the crash wouldn't be a problem. (Although of course the crash should still be fixed).


That's the case with DD disks in a HD drive, e.g. on an AT class machine. A real 1.2MB drive can read 360K disks, so they sort of "belong" to that drive.

Here the 96tpi disk can never be read in the 48tpi drive, so rejecting it is correct - but doing so with a crash is annoying.

On real hardware the Computer's OS would have to decide what to do (Sector not found, Disk Error, Drive not ready) if you can physically cram the disk into the drive.

Maybe our file selector could display some basic data about the disk image (e.g. DD,QD,HD,GCR,FM,MFM, mixed, tracks/sectors/sides), and then load the disk and let the emulated OS do its thing.

This would be a nice approach for machines that were especially praised for their ability to cope with foreign formats, e.g. Commodore 128 or Kaypro II/10.


NCR DMV- DEC Rainbow- Siemens PCD- ITT 3030-Oly People- Acorn A5000- Olivetti M20
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rfka01 Offline OP
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http://www.jbox.dk/rc702/emulator.shtm

has an emulator for the Regnecentralen RC700 (hi Ed! smile )

It's using the same WD 1002 HD0 parallel=>mfm harddisk adapter as the DMV and, e.g. the Kaypro 10.

Maybe something could be ... learned smile from there smile


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rfka01 Offline OP
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Ah yes, now I remember ... I discovered it independently looking for emulators which use the same harddisk controller as the DMV.


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rfka01 Offline OP
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The harddisk controller of the DMV with the internal harddisk is awkward to get at, so I didn't know its type (one of the external ones uses a WD1002-HD0).
With a bit of fiddling in a photo manipulation software, I was able to read the label on one the big chip of the internal controller and then determine the controller type itself.

It's the even older WD1001 that uses the N8X305N microcontroller, belonging to the AM29 series.

As was mentioned recently in the shoutbox, these controllers are the ancestors of the IDE interface.

According to the System Technical Manual Hardware, the internal harddisk adapter goes to slot 2A, the external one to slots 2-6, IFSEL is 4A and it occupies addresses C0H - C7H.


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rfka01 Offline OP
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Scratch the AM29 reference from the last post, it's this critter:

https://en.wikipedia.org/wiki/Signetics_8X300


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We do have a ROM dump from a WD1000 board from a Wicat system in MAME. I wrote an 8X300 core for it some time ago, would be nice to have it do something useful.


- Barry Rodewald
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rfka01 Offline OP
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Sounds great, mahlemiut.

That's the one in the DMV:

K012 Internal HD:

https://dl.dropboxusercontent.com/u/55419307/NCR%20DMV/DMV%20Internal%20HD%20K012.zip

Schematics can be found in the System Technical Manual Hardware, page 258f

and here's a manual for the controller board
http://bitsavers.informatik.uni-stuttgart.de/pdf/eth/lilith/wd1001.pdf


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Ok, so at a quick glance, the WD1001 seems to be a later version of the WD1000, and it does seem to use an 8X305 (I think it has more instructions and such compared to the 8X300, but I'll have to check on that). It'll likely have different code than the WD1000, since it has the later CPU, but if it gets dumped, we can then compare them to be sure.


- Barry Rodewald
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