floppies and the SCB6120

On 6/12/06, David Griffith <dgriffi at cs.csubak.edu> wrote: Given that a _real_ PDP-8 has either an RX8E w/RX01 or RX02, a third-party OMNIBUS board and a propietary interface to a smart drive (a la DSD), or in the case of later DECmates, a local Western Digital FDC chip and a lot of firmware to emulate the functionality (similar IOT scheme) of the earlier techniques, I would say that it depends on which floppies you are trying to support. If you want to support an RX50 on a WD chip, I would think it would be as "easy" as building a daughter card for the SBC-6120 stackable connector that has a WD chip and whatever support components are required, then write a lot of ROM code. If you wanted to plug a _real_ RX01 or RX02 into it, that might be easier - just an IOT decoder on that daughter card, plus the shift registers, etc., to serialize/deserialize the bit stream on the RX cable (i.e., 80% of an RX8E). Given how large the "RX8L" that vrs prototyped (and that I have one of) is, I think you'd be hard pressed to make an RX-6120(?) the same size as the SBC-6120 without programmable parts and/or surface mount. Since the SBC-6120 comes with IDE, if you wanted to write ATAPI support into the ROMs, I suppose you could add support for LS-120 floppy drives (IBM-type HD floppies plus 120MB "uberfloppies"). As currently implemented, though, I'm reasonably certain the SBC-6120 only talks to "true" IDE devices (including PCMCIA flash and CompactFlast). -ethan