6 Jul
2010
6 Jul
'10
11:32 a.m.
The SVA Megaplex was one of my favorites! Two nearly
identical sofware
loops one page apart in memory. One moved a sector's worth of bytes and
the other was an infinite loop. The FDC RDY* signal caused A8 to toggle
when data was available for read or ready for write. IIRC, the board had
2k of SRAM for the firmware. ROM was a 256 byte PROM (unless I'm
confusing this with something else - it's been a while).
Not a disk controller, and certainly not done for speed, but IIRC the
original Apple ][ parallel interface card did something similar. The
status line back from the printer went to an address input on the
firmware ROM<, and thus the code extecuted depended on whether the
printer was ready or not.
-tony