Victor 9000

Let's go through this logically. Virtually all standard floppy drives (and a lot of 'classic' hard drives) rotate at a cosntant speed, which for the purposes of this discussion I'll take as 300rpm (The speed of a 'standard' low density 5.25" disk). So, the disk takes 0.2s to rotate once. Most controllers write the bits to the disk at a constant rate. There are thus a constant number of bits sent out in 0.2s, and thus a constant number of bits (or equivalently a constant number of sectors of a given constant size) written in one revolution of the disk. However, the outer tracks are longer than the inner ones (a simple matter of geometry). So, data bits on the outside tracks take up more area on the disk than ones on the inner tracks. Now, assuming we only need a constant area to store a single bit, it's obvious that space is being wasted on the longer outside tracks. There are 2 ways rounds this. The one used by Commodore on the 1541 and the 8050 (and AFAIK all other classic Commodore drives) was to keep the disk turning at a constant speed (300rpm IIRC) and to write the data bits faster on the outer tracks. Thus, they could write more data in that constant 0.2s I mentioned earlier. The one used by Victor (I believe, I've not seen a Technical Manual) was to keep the data rate constant, but to slow the disk down when writing to the outside tracks (or equivalently to speed it up on the inner ones). The result was that there was more time to write data to the outside tracks, so (at a constant data rate) you could fit more on the disk. In neither case was the number of sectors per track constant (obvious if you require all sectors to be of the same size, which makes writing the file system a lot easier). -- -tony ard12(a)eng.cam.ac.uk The gates in my computer are AND,OR and NOT, not Bill