Denial

I have been wondering about the plus 4 kernel. The same kernel is used in both the plus 4 and the commodore 16. Seeing as they have different configurations with memory size and also the extra roms in the plus 4 is there a routine in the kernel that determines which machine it is fitted into or are the different memories handled purely in hardware?

merser wrote:[...] is there a routine in the kernel that determines which machine it is fitted into [...]?

Yes. That determination is done in the reset routine.

It is possible to provide the C16 and C116 with 64K RAM, that gets handled correctly by the KERNAL. That expansion must be done internally. External RAM expansions don't play nice with the internal DRAMs and TED - they're playing tug of war with the bus signals.

The "3+1" software is viewed as sort of internal ROM cartridge by the KERNAL. You could quite as well put it into an external cartridge and use it with a C16 or C116. The software possibly requires a RAM expansion.

The KERNAL also handles the different main oscillator clock of PAL and NTSC, by adjusting the divider bit in the TED chip (Register $FF07, Bit 6).

Finally, the KERNAL detects the presence of the 6551 ACIA - which is only there in the plus/4.

Thanks very much for the information Mike. That explains it well for me.

Mike wrote:It is possible to provide the C16 and C116 with 64K RAM, that gets handled correctly by the KERNAL. That expansion must be done internally. External RAM expansions don't play nice with the internal DRAMs and TED - they're playing tug of war with the bus signals.

Now that is very important information.

I have seen dozens of times on Amibay and other places people offering RAM expansion cartridges for the C16. This is one very serious problem if people end up with (yet another) dead TED because of these expansions.