Any chance for a Sage / Stride controller capability ?

[Jos Dreesen]

Trying to read some MFM disks from a Stride 440. These have a "homegrown" controller that does away with sectors and it always reads/writes entire tracks, with a dedicated 10Kbyte  SRAM set aside for the databuffer. I can read the raw transistions, but that is it...

Jos

[David Gesswein]

Should work for emulation as long as the data doesn't cross the index pulse.
mfm_util should be able to create emulator file. Don't specify --analyze

If your wanting the extracted track data that will need some work.
Is any information available on the track format? Schematics for the
controller? That will make it easier.

Upload an image to
http://www.pdp8online.com/upload/abuploadab.html
and I'll take a look when I get time.

Also do you need ext2emu support?

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[Jos Dreesen]

Hi David,

My interest is in recreating the data, ( recovering a Unistride UNIX install), I have no intent to use the emulator.

I will upload the zipped transitions file. This comes from a Toshiba MK53FB diskdrive ( 830 cyl, 5 hds).

Still have to convince a Micropolis 1335 ( the well-known stiction problem) and a ST4096 ( broken flexcable ? ) to cooperate...

Schematics for the Sage IV disk controller exist : page 17-21 of http://www.bitsavers.org/pdf/sage/schematics/

Basically it uses a Signetics 2653N CRC chip for errorchecking.

Stride 400, the Sage's successor,  does not seem to have a CRC chip, can't find one on the board . Schematics are not available, but it looks very similar to the Sage solution.

Source code for MFM disk access exists for both Sage and Stride machines, if that is of any help.

If you have time to look at this, I'd appriciate it. And at the same time I understand that ir really is an edge case. How many Stride disks are left anyhow ?

Thanks for designing this great tool,

BR Jos

To view this discussion on the web visit https://groups.google.com/d/msgid/mfm-discuss/20211004192507.GA2488266%40hugin3.

[David Gesswein]

Code is up in the normal locations.

$ ~/corvus/mfm/mfm_util --tran toshiba.raw --ext /tmp/t --format stride_440
Original decode arguments: --heads 5 --cylinders 830 --sector_length 512 --retries 50,4 --drive 1
Found cyl 0 to 829, head 0 to 4, sector 0 to 0
Expected 4150 sectors got 4150 good sectors, 0 bad header, 0 bad data
0 sectors marked bad or spare
0 sectors corrected with ECC. Max bits in burst corrected

I didn't add ext2emu support since you weren't planning to use the emulator.

[Jos Dreesen]

Thanks a lot David !

 Took a while for me to realize that the v2.29  .gz image does not yet contain the Stride-440 stuff, but copying and recompilng the source on the BBB worked a treat.

Image  is now fully captured, now I can go and try to extract the files from the image . Should be feasable as it is a SYS-V Unix variant..

Amazing how little extra code was required for this rather strange Stride format, a tribute to the excellent tool that the MFFM reader is !

Thanks again for the effort you put into this.

BR Jos

[Jos Dreesen]

Uh, make that v2.39... Version with Stride support is  indeed 2.40..

[David Gesswein]

On Sun, Oct 31, 2021 at 10:33:30AM -0700, Jos Dreesen wrote:
> Uh, make that v2.39... Version with Stride support is indeed 2.40..
>

I only update the flash image for generally useful changes.

Did you get the drives that were being difficult working?

[Jos Dreesen]

Not yet tried opening the other disks, will be a task for a quiet December evening...

BR Jos

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