Re: commdore plus 4 cartridges

From: Gerrit Heitsch <>
Date: Thu, 26 Apr 2012 17:51:45 +0200
Message-ID: <>
On 04/25/2012 09:37 PM, wrote:
> any idea of use on the jumpers on:

The jumpers look like they will do the same thing as the jumpers on the 
Plus/4 board. You can use them to change the layout of the socket to 
accomodate a 2364 ROM (the 24pin ones used in the old C64 and 1541).

Since it's unlikely anyone wants to do that, you can leave them out if 
you do your own board and just hardwire it. Anyone wanting to use a 2764 
can do that with the jumpers set for the mask ROMs currently in there.

> any idea of the size of the roms ?

The ROMs are 16KB (23128). They can be replaced by 27128 EPROMs (or 
27256 with the data in the upper half) if one little detail is fixed. 
The 27128 expects Vpp on pin 1 and, in normal operation would like to 
see Vcc (+5V) there. The ROM sockets on the C16 and C116 PCB take this 
in account and have pin 1 connected to +5V. The ROM sockets in the 
Plus/4 do not (all 4 of them) and it look like the cartridge you 
photographed doesn't either. Usually the EPROMs work anyway, but it's 
not according to spec. So if you do your own layout, it would be a good 
idea if you'd connect Pin 1 of each ROM socket to +5V on your board.


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Received on 2012-04-26 16:00:05

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