grr@cbmvax.cbm.UUCP (George Robbins) (12/24/86)
In article <736@vaxb.calgary.UUCP> candym@calgary.UUCP (Mike Candy) writes: > >Does anybody know what controller chip the Amiga uses? If it is an FDC765A >or equivalent, has anybody tried an FDC7265 which is supposed to get 20% >more storage and be "completely software- and pin-compatible"? The amiga doesn't use any standard floppy controller chip. Rather, one of the custom chips (Paula) handles the actually data transfers. It actually transfers RAW bits to and from memory, then some software, with the help of the blitter, does the MFM encoding and decoding. [so i am led to believe] Thus, it is theoretically possible to do RLL (run length coding) or GCR (group coding) and increase the storage capacity. Actually GCR has been a long time Commodore favorite, but with the advent of hard drives, it seems that people are more interested in data interchange than raw floppy capacity. It should be noted, that some drives, both hard and soft, work fine with RLL coding schemes, others require modifications to work reliably. Some problems are limited bandwidth in the read/write circuits and generally inadequate performance margins. SCSI interfaced drives hide all this, and also obviate the need for conforming to the obsolescent ST506/ST512 interface. This is one reason why SCSI may well be the wave of the future for drives, despite the added cost of the SCSI interface. Because the Amiga drives are constant speed, it is unlikely that anyone can come up with a way to read/write Apple/Macintosh disks directly. Perhaps a clever person could do something with the new Mac+ drives, if in fact their speed is externally controlable. -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)