HP9845 service toolkit

Tony wrote: I don't know about the service toolkit. There were apparently major software changes between the 9845A and 9845B. I'm not sure how much hardware difference there is, but I'd expect it to be relatively minor. The 9845B and 9845C are apparently fairly similar in all respects other than the monitor and the graphics control module (monchrome vs. color). However, for the 9845B and 9845C there are two different processor options. The original uses two HP "BPC" microprocessors, as described in HP Journal articles. This is the same 16-bit microprocessor used in the 9825 and 9835, and in various peripherals including the 9872 plotters. Later there was a higher-performance CPU option using commercial bit-slice parts. Probably 2901s, but I've never seen one so I can't say with any certainty. I'd expect that the I/O processor would still be a BPC. The 9845C monitor is apparently the same as used on one of the later HP 9000 Series 500 machines, which were based on the HP "Focus" (the world's first single-chip 32-bit microprocessor), and ran the "Sun" operating system (which had no relation to Sun Microsystems). They ran BASIC or HP-UX layered on top of Sun, similarly to how IBM ran AIX on top of another kernel. Eric