On Fri, 7 Jul 2000, Bo Zimmerman wrote: > I recently received an SFD-1001 with drive select switches. I went poking > around inside the drive and found some things I don't quite understand. I > noticed that the SFD-1001 has no less than TWO 6502 processors. One on the > main board, and another on a small daughterboard above the main board. In > addition, the main board has two 6532s (for the iEEE-488 bus, I expect), but > the daughterboard also has a 6522 near the 6502, and two other chips > besides, marked 251257-02a, and 901885-04. One is a 24pin 2k eeprom. > > I'm curious about a couple of things: whats the 6522 for? Why does a > single drive need two 6502s, and why the daughterboard? Those chip positions do not seem right. See my parts list on funet for the correct chip placement. Basically, the SFD-1001 is a 8250LP with one of the drives missing. The IEEE488 drives all have two processors, one handles the IEEE488 interface and the DOS operating system, the other acts as a drive controller. The 2 6532's are the IEEE488 interface. The 6522 and 6530 are the controller interface. Apparently Commodore did not produce a 6530 with the internal ROM programmed for the SFD-1001. Hence, a small daughter board containing a 6530(any 6530) and an EPROM in what would be the 6530 socket. The daughter board substitutes the EPROM where the 6530 internal ROM would normally be addressed. - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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