some other notes

the Z8536 is listed as the CIO, who's job it is to provide a programmable 
interval timer and a time of day counter (RTC?)

the SCN2661 is the keyboard controller.

Since DUART2 on the AV400 series only uses one port, some of the 
extra register space on the chip is used to provides data strobe and 
data select lines to the parallel interface chip, which I can't see 
because it's under the frame buffer. Interesting method of flow control.

the speaker and associated counter/timer are programmed through registers 
on DUART1, odd.

LANCE AM7990 ethernet - "The LAN interface does not have data buffers; the 
interface uses system memory as its data buffer. The controller has access 
to the first 16MB of system memory, which may be shared with other 
resources. The operating system, via the control and status registers, 
must ensure that the Ethernet controller does not access memory used by 
other controllers. Access to system memory must be carefully tracked to 
prevent overwriting valid data with new data." Well, I guess we can get 
something bigger than an 8k FIFO with this :)

as for 884xx CMU's on the 8500+, I don't know offhand, but I can find out 
in a few weeks if/when the system is taken out of production use(!). Or, 
if I have the 8500 programming book, but I don't think I do. The manuals I 
have in front of me cover the 100,200,300,400,3000,4300,5000, and 6000.


 -- 

The nice thing about Windows is - It does not just crash, it displays a
dialog box and lets you press 'OK' first.
						-- Arno Schaefer