Re: commodore superpet mapping

From: didier derny <>
Date: Tue, 1 Nov 2016 20:56:11 +0100
Message-ID: <>

it's interesting it looks simpler that I expected...
I have 2 projects:
one is to make a board with the following functionalities
     - something like the 6502  rom/ram board
       extended to implement the 64k extension
       I could also extend it to support the superpet ram (enough ram 
available in one chip)
     - vga output
     - usb keyboard

the idea is to have all the fonctions I need with a small board 
connected between the cpu and the keyboard connector...

   one is to make a 6809 board in fact I could have both processor

On 01/11/2016 14:26, Rhialto wrote:
> On Tue 01 Nov 2016 at 13:53:03 +0100, didier derny wrote:
>> if I saw this machine in 1981, I never really had the opportunity to
>> play with it
>> Initially I thought the 6809 was running on it's ram and communicating
>> with the 6502...
>> (a bit like the madison zram with it's z80)
>> recently I found the schematics of the superpet board (combined one)
>> Finally  (apparently according what I saw)
>> 1/  either the  6809  or the 6502 is running ?
> Yes, only one at a time.
>>        6809 stopped by the dma   ?
> There is a hardware switch which usually controls which cpu runs. The
> changeover actually happens during RESET, if I remember well. Although
> there is also a setting on the switch to control it by software.
> However that isn't implemented in VICE I think. I haven't seen any
> software which uses it, so there is no info coming from that direction.
>>        6502 stopped by shutting down the power  ?
>> 2/ the extra memory is only accessed as 16 page s of 4k in 9000 ?
> Yes.
>> 3/ it add a serial port
>> 4/ a protection dongle
> The 6702, which was reverse engineered by this mailinglist and me.
>> Initially I thought the 6809 was running on it's ram and communicating
>> with the 6502...
>> how are the rom decoded ?  I dont really understand...
>> the standard rom are only 'seen' by the 6502 ?
>> the extra rom only 'seen' by the 6809 ? and mapped at the same place ?
> Yes, each CPU sees only its own ROMs even though they are mapped to the
> same address range.
> You can play with it in VICE, select the SuperPET model, and find the
> Waterloo software disk images. The 6809 is not emulated cycle-exact, but
> it is fairly close and apparently good enough for the normal SuperPET
> software.
>> didier
> -Olaf.

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Received on 2016-11-01 20:00:23

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