Date   : Tue, 25 Mar 2003 16:14:36 +0000
From   : Kate Kneebone <kate.kneebone@...>
Subject: Sideways RAM

Hi again,

 Thanks to everyone who's replied to my questions about my two 
computers!  I'll have another look at them tonight with your suggestions 
in mind. I also, have a couple more questions I'd like to ask.  I'd like 
to have a go at producing my own Sideways RAM, just because I have no 
experience at all with actual physical electronics beyond plugging 
things together!  Having had a look at a BBC circuit diagram on the web, 
and with referency to my friendly neighbourhood electronic engineer (I'm 
a mere computer scientist!), I reckon I need to:

o buy a 62256 static RAM chip, which seem to be really cheap, so that's OK.
o stick it in a ROM socket on my chosen computer.
o bend up the A14 pin (1) and connect this up to an unused output of 
IC76 (pin 11 or 12), disconnecting the diode it's connected to, so I can 
address all my 32K.
o bend up the RnW pin (27) and connect this to the computer's RnW line 
from somewhere, pin 3 of IC 26 looks like a candidate from the circuit 
diagram, but I have no clue as to the optimum place to take this signal 
from!

So, my questions are, does what I've just written sound like it'll work? 
And what's the best place to pinch the RnW signal from? Also, as I have 
absolutely no soldering experience (though I've got some friends who can 
hopefully ensure I don't burn the house down!), rather than solder 
anything onto my precious beebs, can I solder onto the RAM chip, but 
clip the other end of the wires onto IC legs with the squeezy, hooky 
things you get on logic analysers (assuming you can buy these somewhere, 
without a few tens of thousands of pounds of logic analyser attached). 
 I *think* I've seen that arrangement on a BBC somewhere before, but I'm 
not totally sure.

Thanks again for everyone's help!


Kate