Re: The EFA microcomputer in slo-mo

Magnus Kesselmark

Just got some fun stuff from Unicorn Electronics, RAM (they forgot a chip!!!), some exotic sound chips and a 1,8MHz X-tal.
The EFA computer was constructed as cheap training device. I will just use the PCB just to have somewhere to place the CPU chip....


----- Original Message -----
From: Richard
To: cosmacelf@...
Sent: Monday, July 05, 2010 8:51 PM
Subject: [cosmacelf] Re: The EFA microcomputer in slo-mo

Looking at the schematic I already found the first thing to enhance. The clock circuit with the 555 timer can't generate much of a frequency. 100 kHz perhaps? Replacing it with a quartz oscillator would be easy, cheap and drastically improve the little computer's performance.

The question is what frequency you might choose. If you want to add a CDP1861 graphics chip you are stuck with the typical 1.78 MHz, else you might even go higher, theretically up to 3.2 MHz (assuming you have a CDP1802ACE).

--- In cosmacelf@..., "Magnus" <tubes@...> wrote:
> Yo!
> I just ordered an 1851 PIO and a PCB for the EFA computer as published in the book Elektronik För Alla (1983). The EFA computer is very simpel as is the PCB, but I wanted something to assemble my ELF on and I will skip some parts and wire the extras up on loose boards. Guess I will end up mounting just the 1802 on the board ...
> For anyone interested, here's the supersimple diagram:
> And this is the board layout:
> Knowing myself, this will enhance my chances of getting something working ....
> /M

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