Contents
I only bought the Commodore C64C because of the 1541-II disk drive. I find floppy disk drives simply fascinating. I want to experiment a little with the KryoFlux here. For this reason, you will find very little information here that is only important to me; this site is not a Commodore C64 website.
R/W-Head
All three photos were taken with the same distance between lens and R/H head. All images were enlarged by the same factor (300%) in an image editing programme, centred and cropped in 500px/500px format.
- 1541-II .. 48 tpi .. 35 tracks .. straddle erase
- FD-55A ... 48 tpi .. 40 tracks .. tunnel erase
- FD-55E ... 96 tpi .. 80 tracks .. tunnel erase
From the above figure it can be „visually“ deduced that the „geometry“ of the 1541-II R/W head is a classic 48 tpi head, but ...
... the stepper motor of the 1541-II is capable of accessing a total of 84 tracks, unlike the DOS PC 48 tpi drives [1]. However, since the R/W core is a wide 48 tpi core, the 1541-II drive software must always skip a track, the so called double-stepping. This is exactly how a 1.2 MB drive works in 360 KB mode.
The 1541-II and also the other Commodore drives were therefore able to access "half" tracks. These half tracks were used by some software manufacturers as a copy protection mechanism.
The R/W head of an 96 tpi drive is (nearly) half the size of an 48 tpi drive. „(b) 1.2 Mb“ basically means an 96 tpi drive (or 80 tracks). The TEAC FD-55E is an 96 tpi drive.
Footnotes
- Buy on Tindie: Copy Protection Methods
- Copy Protection Methods