TeleDisk Archives

[Dave Frederickson]

I get most of the software for my 85B from the HP Computer Museum's archives. There's an issue in that some of the discs imaged with TeleDisk on non-blank media. Consequently some of the images contain bogus data like data on side 1 of a single-sided disc or extra tracks.
With the recent acquisition of a Greaseweazle it seems that I have the opportunity to cleanup some of these images.
The question is what's the best format?
1. A linear sector dump, like the images provided with the HP-85 emulator, which produces images 264k in length for a 3.5" SS/DD disc. Convenient for emulator users.
2. A flux image produced with Greaseweazle. This image contains info like sector interleave - crucial for exact reproduction of vintage discs.
3. An intermediate format like TeleDisk or IMD which retain some low-level info. There are two issues with this format. First, TeleDisk requires vintage hardware and IMD can't handle tracks with differing sector sizes. Apparently many of the 3.5" SS/DD discs from HP contain an extra 17th sector of 128 bytes to be used for media wear data. LIF images with 17-sector tracks are 280k in size.
It has been suggested to provide all three formats.
https://groups.io/g/VintHPcom/message/10731

Both VP at HP Series 80 and Dave Collins the HP Computer Museum have already offered to host the updated files.

-Dave

[BruceH]

Maybe both 1 and 2?

Option 3 seems to be the least convenient for all potential users.

[Dave Frederickson]

(11-19-2024 11:30 PM)BruceH Wrote:  Maybe both 1 and 2?

Option 3 seems to be the least convenient for all potential users.

I agree. Seems like TeleDisk doesn't produce accurate copies if not used correctly. Take the 85 Games disc on the Computer Museum's site. Analysis shows that this disc was originally an 80-track, 9 sectors-per-track (IBM) disc which was overwritten on side 0, tracks 0-69 (9121 format), by TeleDisk. The disc functions normally, but it's not what I'd call an archival copy.
Even GreaseWeazle will faithfully create images of discs with read errors. Recall that recording sectors with bad data was an early form of copy protection. Consequently, .TD0 images like 85 GAMES II, on the Computer Museum site, while having no extra tracks, does have several erroneous sectors.

BTW, the disc structure of .TD0 files can be viewed with the floppy emulator, HxC.
1. Load the .TD0 file.
2. Select Track Analyzer
3. Select View Mode: 3"1/2 135 TPI