3 Jun
1999
3 Jun
'99
4:28 p.m.
Well . . . it seems to work, now that I've fiddled with the broken jumper
wire. The wire was broken but the insulation wasn't, and it was done so
neatly, I couldn't initially believe it was a user-installed jumper wire.
Now that that's done, I can put it in the "works" box . . .
Thanks for the help.
Dick
-----Original Message-----
From: Marvin <marvin(a)rain.org>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Thursday, June 03, 1999 7:04 PM
Subject: Re: VECTOR GRAPHICS 64K DRAM Card - switch settings?
Richard Erlacher wrote:
Would anyone be able to help me with this VECTOR GRAPHICS 64K DRAM BOARD's
switch settings? The signals seem to be OK, but no data propagates from
the thing. I'm not anxious to count through the combinations of
settings.
According to the schematics for the Rev-3 board, S1 is the Bank Select with
positions 0 - 7 (or probably labeled 1 - 8) corresponding to D0 - D7. D0 -
D7 go through 74175 Quad D latches and come out on the Not Q outputs. These
are then all anded together (U41 - 74ls30) to output the Bank Select signal.
Hmmm, interesting, it looks like the inputs are left floating when the
switch is open, and I have a hard time believing that with LS type
circuitry.
There is a note indicating:
Jumper Memory Enabled
1 to 3 0000h - FFFFh
5 to 3 0000h - DFFFh
4 to 3 0000h - BFFFh, E000h - FFFFh
2 to 3 0000h - BFFFh