ZX81 kits (was Re: Keep or assemble???)

From: Glen Goodwin <acme_ent_at_bellsouth.net>
Date: Fri Sep 28 23:37:08 2001

> > The ULA does a lot more than handle the display ;>)
> CPU clock generation (which would be useful). Address decoding (which I'd

> want to modify if I was changing the amount of RAM).

Very interesting -- how much RAM are you talking about adding that you have
to modify the address decoding?

> > Of course not ;>) But a ZX81 kit is still faster than starting from
> > scratch.
> Is it? It's not going to take long to wire-wrap a clock circuit and
> address decoder, and stick in the Z80. It depends _very much_ on how much

> of the ZX81 you want to use...

Which in turn depends on what the intended use of the finished device is.
Since I want a "general purpose" computer the ROM BASIC functions are very
convenient, and fast if called directly. Other applications of the Z80
would not need this code so a quickie Z80 board would be fine.
> > Try desoldering the RF modulator from a ZX81 board ;>)
> Well, I had never tried to do it before, so I grabbed a ZX81,

What, do you have a pile of these?

> unscrewed
> the case and attacked it with soldering iron and sucker.
> What's the catch?

In the US versions which have 3 thin wires, they sometimes become brittle
and break.

Tony (and others), a question: in your opinion, which microprocessor was
the most well-designed (even if not implemented)?

Received on Fri Sep 28 2001 - 23:37:08 BST

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