29 Mar
2002
29 Mar
'02
8:40 a.m.
The only difference between the 2016 and the 6116, is tha the 6116 is CMOS,
while the 2016 is NMOS. That's not much difference.
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, March 29, 2002 2:12 PM
Subject: Re: ZX81 and 6116
As did my PCB. If you use 2114s, L1/L2 makes no difference (it's not
connected to these chips at all). Might as well save 1cm of wire and a
bit of solder :-)
> All but one of the 2K boards had a single 2016 and L2 was installed.
> One 2K board had a 6116 and L2 was installed. The board was operational
> and appeared unmodified.
> I replaced a socketed 2016 on a working board with the 6116 pulled from the
>
> > So, fit L2 if you install a 6116 (A10 on pin 19). Fit L1 if you install
a
4118 (I am not sure what pin 19 is, I can't
find a 4118 data sheet, but
at least one schematic I have calls it 'E', presumably an active high
enable signal). Fit either or no links if you install 2 * 2114s. Never
fit both links, or you'll short A10 to the +5V rail.
Today I checked out about two dozen ZX81/TS1000s. They've been piling up
in a box and today I finally got to them. Here's what I found:
All of the 1K boards had two 2114s and no jumper installed.
above-mentioned board,
and the board still worked.
The 2016 and 6116 are essentially the same chip, made by different
manufacturers. There are other chips with other numbers that are
essentially equivanet too. All are 2K * 8 static RAMs, pinout like a 2716
EPROM with WE/ on pin 21. I am not suprised that they are interchangeable
in the ZX81.
So I think it's safe to say that L2 is required for a single-RAM-chip
board, and that a 6116 is a drop-in replacement for a 2016.
The first part is a false conclusion. It's safe to say that L2 is needed
for a single-chip _2K_ machine (using a 6116 or similar), which is what
we've been saying all along. For a single-chip 1K machine (using a
4118), you use L1. You've not seen one of those boards, so you've not
seen a machine with L1 fitted.
-tony