Re: Disassembly of the Z80 ROM of the C128

From: Clockmeister <>
Date: Wed, 1 Mar 2017 08:26:02 +0800
Message-ID: <>
On 1/03/2017 8:02 AM, smf wrote:
> On 28/02/2017 15:06, geneb wrote:
>> Patches that were done were applied to the BIOS, not the ROM. Keep in 
>> mind that under CP/M, the BIOS is loaded off of disk and isn't 
>> ROM-resident.  CP/M is kind of a stack.  The BDOS, the BIOS, and the 
>> CCP. The BDOS is the same for every CP/M system. The BIOS is modified 
>> to match the hardware that CP/M is running on, and the CCP is 
>> basically equivalent to COMMAND.COM in DOS - it's transient.
> The phone call was about the boot ROM for the Z80, that worked out 
> whether to go into C64 mode or C128 mode. Before that call the 6502 
> started first & it tried to handle the mode switch, but that caused a 
> problem with the magic voice cartridge.
> It had nothing to do with CPM.

It makes sense to use the Z80 to handle the mode switch since after 
reset it starts running whatever code is at address 0000h.

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Received on 2017-03-01 01:00:55

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