Re: Putting a RAM chip in U36 on a C128

From: Niklas Ramsberg (
Date: 2002-08-21 21:26:58

On Wed, 21 Aug 2002 20:44:19 +0200
"Spiro Trikaliotis" <> wrote:

> I don't know that much about U36 on the C128, but are you sure that
> the PLA gives a CS if you try to write to that area? It might be
> something like the "RAM-under-ROM"-syndrome on the C64, where you
> can write to the RAM under KERNAL or BASIC while the ROM is selected.
> If the CS is not generated on write, the R/W logic is not that simple 
> anymore.

Hmm... I think you're right. In the memory configurations where the chip in U36 (internal function ROM is what Commodore calls it) is seen by the processor, AFAIK it works like any other ROM in the computer; i.e. when you read from that area, you read from ROM, but when you write, you write to RAM. I don't know if there is a way to change this behavior. I'll check my reference books.


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