Re: ][+ Video card question(s)

[dempson@actrix.gen.nz (David Empson)]

In article <34np3q$epu@kelly.teleport.com>,
Gerome Manufacturing <gerome@teleport.com> wrote:
> Hi!
> 
> 	I just picked up a II+ for 20$ today, and it has an 80 column card
> in it made by videx.  I found that using escape+ one of the number keys
> would change through various text modes ranging from 80x24 to 160x24.  There
> are a number of connectors and jumpers and dip switches on this thing.  Does
> anyone have some information describing what they do?

I have a manual around here somewhere...

> 	There is a wire connecting from somewhere around the game port to
> somewhere near the keyboard.  (sorry I am at work and don't know the exact
> pins & chips...)

Sounds like a shift-key mod to me.  The wire should be running from
the second pin from the edge opposite the power supply on the connector
between the keyboard and its piggy-back board (pin 24 if counting from
the other end).  It should go to one of the game port pins (pin 4) or
to pin 1 of a nearby 74LS251 (at board location "H14").

This wire connects the SHIFT keys to the "Switch 2" input on the game
port (which is infrequently used).  It allows programs to sense the
state of the shift key by watching the SW2 I/O location ($C062).  If
bit 7 is set, then the shift key is up.  If bit 7 is clear, then the
shift key is down.

> A friend told me that was the double hi-res hack, and that
> a person can get the II+ to do it, if a wire connected two points in
> the computer.

I find that very hard to believe.  The IIe (except the original
revision A motherboard) can do double hi-res graphics, and requires a
jumper installed on the earlier model of the extended 80-column card
to enable this.

Double hi-res graphics needs an additional 8k of RAM in the auxiliary
bank.  The II+ has no hardware support for auxiliary memory.  Its
video circuitry probably doesn't support double hi-res either.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand