VECTOR GRAPHICS 64K DRAM Card - switch settings?

From: Marvin <marvin_at_rain.org>
Date: Thu Jun 3 20:00:27 1999

> 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
Received on Thu Jun 03 1999 - 20:00:27 BST