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Didn't OSI call the two sides of the first drive A and C, and the two sides of the second drive B and D? Wouldn't it make sense to stick with that if possible? It may not matter with 65D, but it would with another operating system (like 65U) which keeps track of the head positions of the two physical drives.

I don't think the drive can be made to step two tracks on one step command. On a PC, the drive type is in the BIOS, so when reading or writing a 360 kB disk in a 1.2 MB drive, the DOS would know to issue two step commands for each track it wanted to move.

@Klyball I made the first three changes to my OS on track 0 but I changed them to support 80 tracks. Is the 4th change for sectors per track? I'm perfectly happy with 8 sectors per track as I don't need all that space and I don't want to mod all the apps on the tutorial disks to support 8" mode. Also, I don't want to re set all the timings. My separator is on the underside of my board and it is hard to reach for adjusting.

So far the drive has been rock solid with absolutely no errors, not even when writing to track 79.

Can the 1.44 be used in a similar fashion without major modifications? The only changes to the Epson were changing the jumpers.

/Jeff

@Jeff,
Yes the 4 change is for sectors, I agree if your system is originally set for 5.25 drives, using a 720k floppy would be ideal,
most 1.44 drive need the drive select changed from ds1 to ds0 and thats usually on the circuit board, plus the ready signal needs to be changed to pin 34
, then you would need to cover the density hole on the floppy but it would need to be dual density drive.

here is a example
5.25" 90k drives = 5.25 360k /3.5 720k drives little or no changes
8 " drives = 1.2m 5.25 drives (have not tested)will work modification unknown at this point
8 " drives = 1.44m 3.5 drives need modifications(tested and working)

Grant,

I'm assembling the D-13. Very exciting. Quick question... Which one of the .156 connectors is Pin 14 and which one should be connected to pin 1 on the original OSI 610 board? Just want to make certain I match up the D-13 with 610 correctly.

Thanks

Don't forget to add the +5 to pin 14 on the 610 ,why they left it out hmm

Ok, here is the mod for dual 2 sided drives.

The data separator unmodified, is set to run dual one sided drives with no modifications to it or the OSI controller.
For dual 2 sided drives we need to add a hex inverter in ic 3. and modify the D-13 and 610 or whichever OSI controller you are using.

Tested with a sony FRU 76H4091 1.44 floppy as drive A,C and a Shugart SA850 as drive B,D

Life has been interesting in the house in the woods recently. However, I have been getting moments here and there to work on this project. The drives I'm using, old Radio Shack external drives initially designed for the TRS-80 model 1, 3, 4 and COCO, require the motor control line to be brought low for the spindle to spin. Is this not the case with the drives the rest of you have been using?

I know the rest of the controller seems to be working as I can operate the drives using BASIC statements that emulate what the monitor code is doing. All except get the spindle motor to start up. I'm going to put the inverter in and jumper pins 13 & 14 to see if this works for these drives. I'd like to get them working as they are nice, self-contained units with their own power supplies and cases.

So far using the KLyball 610 board with my original 600 board the memory errors are completely different than with my memory board. They are still there, but very different. What happens with the 610 board is that on every 16th run through the memory test almost every byte between 12352 and 13311 shows an error such that the value is off by exactly 16. I'll get the errors on the 16th run, the 32nd run, the 48th run, etc... Never do I get an error on any other run, or in other locations. I've replaced the memory in that 1K block and the surrounding blocks. Same thing happens. The code I'm using is below, modified to concentrate on those locations. It would be great is someone else could give it a shot and let me know what they get.

@bill,
You can just jumper 14/15 to pull motor low
My mpi drives and shugart drives are just on at power up ,the new drives im using require the line pulled low, you can use a inverter or just ground

You will need the inverter if you are going to go to 2 sided drives anyway

Both ways work fine

I have attempted to transfer the jumper settings for Dual Sided Drives on the 610 to the 505.

Here is what Klyball recommended for the 610: (3 cuts, 3 Jumpers) Here are my results: (3 cuts, 3 jumpers) /Jeff

here is another view