Northstar DSDD MFM Disk

[pauldevine]

Hi David, Hope you're doing well. I've been having trouble getting clean recordings of some Northstar hard sectored disks. They're DSDD MFM encoded disks as far as I can tell. I have a few .flux images here: https://drive.google.com/drive/folders/1HpM2vL5TIh3pgk7pFHuavaec8F7z8J-b?usp=drive_link

When reading the disks I'm having a number of sector errors:

H.SS 0123456789012345678901234567890123456789
0. 0 ...?.....B.......B.B...B.?.?.?.?.?.?.?.?
0. 1 .?.?...B.?...B.?.B.B.B.B.?.?.?.?.?.?.?.?
0. 2 .?.?.....?.....?.?.?.?.?.?.?.?.?.?.?.?.?
0. 3 ...?.....?.....B.B.?.?.?...?.B.?...B.?.B
0. 4 .........?.....B.B.B.?.?................
0. 5 ...?.....B.......B.....?................
0. 6 .........B..............................
0. 7 ...?.....................B.B.B.B.B.B.B.B
0. 8 .B.?.....C...........?.?.?.?.?.?.?.?.?.?
0. 9 .?.?.....C...........?.?.?.?.?.?.?.?.?.?
1. 0 .....B...?.B.?.B.?.B...?................
1. 1 .B...?.B.?.?.?.?.?.B...?.B.B.B.....B.B.B
1. 2 .?.....C.?.?.?...?.B...B.B.?.B...B.B.B.?
1. 3 .?...?.?.?.?.?.?.?.?...B.?.?.?...B.B.?.B
1. 4 .....?...?.B.B.?.?.?...B...B.......B.B..
1. 5 .....?.B.?.?.?.B.?.?...?................
1. 6 .......B.?.?.?.?.?.?...?................
1. 7 .......B.?.?.?.?.?.B...?................
1. 8 .....?...?.?.?.B.?.?...?................
1. 9 .....?...?.B.B.B.?.B...?.?...?..........
Good sectors: 727/800 (90%)
Missing sectors: 0/800 (0%)
Bad sectors: 73/800 (9%)

The disks seem relatively physically clean. I'm reading them on a HD drive. I've been playing around with the settings and the best read so far as come from: ./fluxengine read northstar --350 40track_drive -s drive:0 -o northstar_kermit.nsi --copy-flux-to=northstar_kermit.flux --decoder.write_csv_to=northstar_kermit.csv --drive.revolutions=4.2 --drive.hard_sector_count=10 --drive.high_density=0 --decoder.retries=3

A few questions for you, would I have better luck reading these on a DD drive? Also, I noticed in your test data the northstar disks are labeled synthetic. Would you appreciate recordings from actual disks? Does anything look amiss with these recordings? I'm trying to get a clean disk so I can validate the emulator I'm using is working well. Any advice would be appreciated.

[davidgiven]

That looks well weird. Are you sure it's a 40 track drive? This looks exactly what I'd expect to get from a 40 track disk in an 80 track drive and 40track_drive set.

Re disk images: I'm looking for a flux file of a blank disk as formatted on a real NorthStar. (It needs to be blank for ease of analysis and to avoid copyright issues.

Incidentally, do you know anything about the file system used on the NorthStar? It'd be interesting to do a driver.

[pauldevine]

It is a 40 track disk in an 80 track drive. I wasn't sure if that was an allowable combination or not. I'll see if I can track down a 40 track drive.

I have about 100 Northstar disks, but I'm not sure if any of them are blank. There's a non-zero chance one of them would be.

I'm just learning about Northstar disks. I'm trying to make sure I'm doing a reasonable take at archiving them. This time around I don't have the hardware and I'm seeing it's easier to validate what's going on when you have the legacy machine sitting in front of you.

[davidgiven]

Right --- try it again without the 40track_drive. You only need that if you actually do have a 40 track drive.