Thanks, Platypus, old contact data not needed. But you gave me some more ideas. I could compare how the numbers line up for 3.5" amound the various alternative DOSes and see if my 'method' holds true on that disk platform.

I do need 5.25" data though and the only one I don't have yet is 160k single side which is what DOS 1.0 is. Can anybody suggest an earlier DOS or alternative DOS on 5.25"?

Thanks for all the posts everybody, I didn't think there was that much activity in here.

Seattle DOS was the name before Gates got it, and it was also known as Quick and Dirty DOS shortened to QDOS. Still, so close to CP/M, that Digital Research sued over it.

What we are doing is trying to reprogram the system to write out boot disks on the PC that will boot the old Atari 8 bit. It almost works too! So now we need to tweak things a bit and I just want a solid base of tables that do work so that we can get the fiddling done with in a hurry. Further complications are 288 RPM on Atari drive and sector size limited to 128 bytes. So I'm actually trying to build a table for 130k disks from 180k and 160k tables. The more 5.25" tables I can get, the better idea of just what is optimum values for total head write time per track. Adjust that for RPM and we should really be close. Thanks.