Trouble in paradise

[Norman Yarvin]

In article <221 at usna.NAVY.MIL> trw at usna.NAVY.MIL (tsmith <trw at usna>) writes:

>dumb.  I checked the LEDs and the green one lights but there is no other
>activity.

Aha!  From the reference manual:

red	yellow	green	red	failed...
off	off	off	on	 telephone initialization
off	off	on	off	 video RAM test  <------------------------
off	off	on	on	 map RAM test
off	on	off	off	 to set map RAM to unity map
off	on	off	on	 dynamic RAM test
off	on	on	off	 initialization
off	on	on	on	 to find loader

Suggestions: the usual -- power cycling, dusting it out, reseating cables
and chips.  The video RAM seems to be 4 4416 chips at positions 17A, 16A,
15A, 14A if I'm reading the schematics right.

>At the same time could someone tell me if anyone has looked into replacing
>the 64K memory chips with 256K chips? I seem to remember that the only real
>difference in the chips is pin 1 (on 64K chips it is NC and on 256K chips
>it is A8.)  It would be nice if I could put 2MEG on the motherboard.  And
>maybe even on the expansion board as well.

It has been done; refer to jbm at uncle's HWNotes (archived at osu-cis.)

Norman Yarvin		yarvin-norman at cs.yale.edu