Le 02/05/2012 07:50, Baltissen a écrit : > - ROM from a 1591 disk drive - the high density 1581 - heard prototype > was thrown away :( > > To be honest, I haven't an idea what hardware is needed to run a 1.44 MB > drive at all. FYI, I have never seen the insides (or schematics) of an > CMD FD2000. For example, is DMA a must? If it can be run using the 1581 > hardware, IMHO two things have to be done: > - the 1581 stores a complete track in memory. If we want to do that here > as well, at least 8 KB have to be added. > - change the sofware. OK, I know this is obvious but it can be done in > two ways: > - with the RAM expansion: just double the number of sectors/track > - without the expansion: read/write every track like it is done on a > 1541 > FYI, in some spare times I'm still busy with 1581IDE project so I dare > to say that I know where I am talking about. > > > Hi, it may be a problem of speed, on a standard floppy 3 1/2 floppy as far as I can remember, we have 13 or 14 microseconds to transfer the data. with a HD it's probably faster and probably why a dma is needed. on the 6502 the commodore floppy disk controller they are using the SO line (set overflow) and the assembly code: NEXT: CLV ;- 2 cycles LABEL: BVC LABEL ;- 3 cyles LDA PORT ;- 4 cycles here overflow is set and the data are ready STA $BUFFER, Y ;- 5 cycles INY ;- 2 cycles BNE NEXT ;- 3 cycles ____________________________ ;- 19 cycles (I used something similar to read a 3 1/2 floppy disk with a 6809...) on a 3 1/2 HD disk we probably need either DMA or a faster speed for the processor I dont remember very well the details but it was the origin of the problem and the use of SO line -- didier Message was sent through the cbm-hackers mailing listReceived on 2012-05-02 10:00:32
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