ZX81 and 6116

From: Stan Barr <stanb_at_dial.pipex.com>
Date: Wed Mar 27 12:56:52 2002


classiccmp_at_classiccmp.org said:
> > From: Tony Duell <ard_at_p850ug1.demon.co.uk>
> I wrote:
> > > After checking the schematic I find that there is a link. "Use L1 for
> 1K
> > > RAM, use L2 for 2K RAM." This tells me that when a 4118 or two 2114s
> are
> > > used (or a 6116???) there is no need to change the jumper -- it's only
> > > required when using a 2KB 2016 or equivalent.
> Tony replied:
> > What is this link connected to? What does it reconnect?
> Ok -- I have yet another version of the schematic here, and it agrees with
> the first -- L1 for 1K and L2 for 2K but does NOT specify what this means
> in terms of the actual number of RAM ICs onboard.
> >From looking at the schematic from the ZX-TEAM web site, I can't see how
> either jumper would affect a two-chip configuration. L1 ties the single
> RAM chip's A10 to +5V, while L2 ties the single chip's A10 to the A10 line
> on the system bus.
> Can you make any sense out of this, or is it necessary to be Clive Sinclair
> in order to understand it?
> As mentioned in a previous post, the 2-RAM-chip ZX81 PCBs I have at hand
> have NEITHER L1 or L2 installed.

Just to confuse things further the schematic I have shows L1 pulling pin
19 of the 4118 up to 5V when that's installed, and no L2 at all!
The text refers to 2x2114 or a 4118 installed in the UK version and a
2K option for export - possibly there are 2 versions of the board?
Stan Barr  stanb_at_dial.pipex.com
The future was never like this!
Received on Wed Mar 27 2002 - 12:56:52 GMT

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