What are the really unusual or weird computers?

On 28 Jun 2007 at 18:43, Fred Cisin wrote: One of the more useful things to have around in this respect are the Phoenix BIOS books. Not only do they call out what gozinta and gozouta each BIOS routine, but the memory cells used by each routine and what they contained--as well as the entry point address of each routine (some early code simply did a far CALL to the BIOS routine entry point). But even that wasn't perfect. Way back whne in the PC-AT days, I wrote a little program called AT720K or something like that that allowed one to use a 96 tpi 5.25" 720K diskettes in the 5.25" 1.2MB drive under DOS without loading any drivers. It simply intercepted the BIOS INT 13H vector and reset the "double step" bit in low BIOS RAM for a particular drive. Problen was that it worked for a *lot* of "AT-compatible" BIOSes, but not all. Seems that some vendors decided to define their flags differently. BIOSes were hell back them--I still have a whole load of BIOS snapshots somewhere as debugging detritus. I used to send a customer with a BIOS problem a boot disk that grabbed the BIOS image and wrote it to floppy. The customer sent the diskette back and I had my sample to scratch my head over. Cheers, Chuck