A1 jumper description?

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Joined: Oct 15 2013
Posts: 17

Is there a description available anywhere of the possible jumper configurations for the jumper pad above the 74154 on the Apple 1 board? I saw the recommended jumpers in Mike's A1 Mimeo assembly manual, but was wondering if there was a detailed description available anywhere?



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speedyG's picture
Joined: Nov 16 2011
Posts: 2426
Re: A1 jumper description?

Only the plain text explenation....
RAM-chips at row B are refered to by X
and RAM-chips at row A are refered to as W.

And that explenation just tells that factory setting is:
Bank X is connected to 0000 ( Program storage area )
and bank W is connected to E000 ( because the Basic interpreter is loaded to that location ).

The ACI ( Apple Cassette Interface )manual tells that it is set to adress C000.
So that area may not be used by the RAM on the mainboard.

And if you instead use the CFFA for the Apple-1 then it´s at least
using the adressingspace at A000 by the wireline T.

If you want to add the CFFA then it may also be set to use additional
adressing space from 1000 to 7FFF ( by selection of switch 2 at the CFFA board.
So it´s recommended not use that space either by the RAM of the mainboard.



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Joined: Oct 15 2013
Posts: 17
Re: A1 jumper description?

This is helpful, thank you.