Boards with an 8X305 CPU (was Re: IBM 5161)

The 8X300 and 8X305 were commonly used in 5.25- and 8-inch hard drive controllers for microcomputers starting around 1980. Most of these were based on the Western Digital WD1000 design, the legacy of which can still be seen in today's ATA (IDE) drives. The 8X300 was a single-chip version of an earlier processor design by Scientific Micro Systems (SMS). The 8X305 is a slightly updated version of the 8X300. I'm not sure what the specific differences were. The 8x300/305 is AFAIK the only chip produced in a 50 pin DIP package, with 600 mil row spacing. ISTR that the 8x300 may have used I2L (integrated injection logic) rather than TTL. I2L offered some advantages at the time, but never really caught on. TI used it for some parts as well, such as the SBP9900, a bipolar version of the TMS9900. Eric