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Lotharek floppy EMU and controller hacking...


aftyde
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Hi All,

 

Way out of my depth here... but I read that the 80 track mod for the TI controller basically boiled down to a two byte change in the ROM. That got me thinking - with the Lotharek Floppy Drive emulator - you can define any sort of diskette you want and mount the thing. So - what if I did something like this...

 

80x80x256

 

and created an 80 track, 80 sector (256 bytes per sector) image...

 

That would be a 12800 sector floppy image - enough space where I'd stop complaining for a while... ;)

 

So I'm wondering - what outlandish figures could I pop into a ROM, match to the Lotharek and give it a go. Would probably need tidir support for formatting these images as the Lotharek tanks on disk init commands. (but seems to read and write to converted images with no issue)

 

Possible - or wishful thinking?

 

Cheers, Arthur...

Edited by aftyde
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Changing the number of tracks is one thing, the number of sectors quite another.

 

The controller cannot likely keep up with the data rate that would be required to read that from the (emulated) disk.

 

Consider that a 300RPM disk is feeding data to the controller at 200000/6450=46.5ms per byte.

You are asking it to instead read 200000/(80*364)=6.8ms per byte.

 

Now that is if the floppy drive is emulated at the low level I think that the HxC does. If it actually could fake out the controller to feed data in at the normal rate but a much larger track, you might be able to do this. I don't think this is the way it works. The index signals would be much further apart and I think this logic is embedded in the 179x controller chip, not in DOS ROM.

Edited by R.Cade
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I don't know enough about the Lotharek DSR to have the complete answer; but, a simple TI-type floppy image only has enough room in the sector map for 1600 sectors. Obviously, if the Lotharek is capable of 2880-sector images (as you posted elsewhere), it is doing something different from the TI DSR and likely dependent on the SCSI controller you have it attached to. Also, from your other post, it would appear that is controller dependent, so without rewrites of CorComp or TI DSRs, 1600 is probably the limit with those controllers. As you may know, that is what Jaime Malilonmg did with the CF7/nanoPEB image volumes.

 

...lee

Edited by Lee Stewart
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I am counting on the Lotharek to maintain a steady data transfer rate. I'm guessing (hoping) that since it's reading from a flash card no matter what diskette image is mounted - that it probably regulates the speed at which it talks to the controller. I have tried, for example with the Corcomp - to change the step speed from 10ms to 3 or 6 - and the Lotharek didn't seem to like that. The Corcomp diagnostic sees the disk "spinning" at exactly 300 RPM and it seems to like the step rate at 10ms.

 

I'd certainly be willing to burn some ROMs for the TI controller and experiment a bit.

 

Changing the number of tracks is one thing, the number of sectors quite another.

 

The controller cannot likely keep up with the data rate that would be required to read that from the (emulated) disk.

 

Consider that a 300RPM disk is feeding data to the controller at 200000/6450=46.5ms per byte.

You are asking it to instead read 200000/(80*364)=6.8ms per byte.

 

Now that is if the floppy drive is emulated at the low level I think that the HxC does. If it actually could fake out the controller to feed data in at the normal rate but a much larger track, you might be able to do this. I don't think this is the way it works. The index signals would be much further apart and I think this logic is embedded in the 179x controller chip, not in DOS ROM.

 

I recall reading about that... The Lotharek supports 2880 with the Myarc controller 80 track DSDD mode. The Lotharek is a floppy disk emulator - I've tried it with TI (40 and 80 track), Corcomp (40 track DS), and Myarc (40/80 DSDD). I have no idea how the Myarc controller achieves 2880 but it seems to work as I have database files in excess of 1800 that seem to work OK.

 

I don't know enough about the Lotharek DSR to have the complete answer; but, a simple TI-type floppy image only has enough room in the sector map for 1600 sectors. Obviously, if the Lotharek is capable of 2880-sector images (as you posted elsewhere), it is doing something different from the TI DSR and likely dependent on the SCSI controller you have it attached to. Also, from your other post, it would appear that is controller dependent, so without rewrites of CorComp or TI DSRs, 1600 is probably the limit with those controllers. As you may know, that is what Jaime Malilonmg did with the CF7/nanoPEB image volumes.

 

...lee

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Whoops - you are right actually... I was debugging a SSSD 90K TI drive that went south on me when I was tinkering with the timings. Lotharek's were OK.

 

 

hmmm, the Lotharek-drive should run very fine at 3,6,10ms (or at any other ms, on "any" system/controller), also with Corcomp.

For me, it seems to do.

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.

No, I think not. This is due to the CC-9900 controllers (and some other) DIP-switches, where you can setup the ms for the drives.

This is not given on the TI-Controller, only via Eprom-Update (6/12ms-BINs are available, IIRC)

 

hmm, so my question is now, what about the 80track-mods, which ms are they set to ?

 

xXx

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