Re: CBM-900 floppy disk format/encoding

Hi Simon,

On 2012-01-06 00:20, Simon_Laule wrote:
>
> According to the 8723 datasheet, this is really the case:
>
> ...
> GCR FORMAT
>     The Z8000 computer will run a version of the unix operating system
> and will require a 512 byte sector size. This format will use the
> existing commodore GCR data encode scheme with variable density (see table
> 3.2.2).    This format will allow for 1.224.704 bytes of storage per
> drive. The data rate for one track will vary from 41K to 33K bytes/second.
> for the different regions. Th multi-track transfers including step settle
> and latency will be 38K to 33K bytes/second.
> ...
> Table 1.7.4 GCR DATA RATES/FORMATTED CAPACITY
> TRACK REGION     BIT TIME     SECTORS/TRACK    SECTORS/REGION
>   1-39                           2.16                       16
> 624
> 40-53                          2.33                       15
> 210
> 54-64                          2.50                       14
> 154
> 65-80                          2.66                       13
> 208
> SECTORS/SIDE          = 1 196
> SECTORS/DISK          = 2,392
> BYTES/DISK               = 1,224,704
> BYTES/CONTROLLER= 2,449,408
> ...
>
> If I remember correctly, this is the same feature as in the 8280,
> 80 tracks with sectors on both sides,
> whereas the 8250 (as expanded 8050) sees first the 80 tracks on one side,
>   then the 80 tracks on the other side.
>
> On the other hand, I never tried to read a c900 disk in a 8250 or SFD1001.
>

Could you point us to where we can find this datasheet for the 8723 ?

Thanks in advance

Kind regards Uffe





       Message was sent through the cbm-hackers mailing list