Least PC-Compatible MS-DOS machines?

THat relaly depends on how you define 'bit rate'. I will agree that the number of bits /track is not constant over the disk. The Sirrius format is somkewhat related to the Commoodore 8050 format (to the extent that the scheamtics of the encoder/decoder section are very similar). However there is a difference. The Commodore 8050 rotates the disk at a cosntate speed (I am pretty sure it's 300 rpm)(. The date clock circult can produce 4 different clock rates, the apporpriate one is selected depending on which track the head is on. In the commodore drive, therefore, the data rate is higher on the outer (longer) tracks. More bits are thus stored on said tracks than on the inner ones, the density in bits/linear inch is more nearly constant across the disk than on a normal constant wpeed, constant data rate, system But having a changing data rate apparently lead to complciaitons in the design of the filter i nthe read ampliifer circuit. TheSirrus gets round this by having the same data clokc rate acorss the disk. But the rottional speed of the disk varies. It turns slower when the heads are over the outer tracks, so that (given the constant data clock rate), again more bits are stored on the outer tracks. -tony