It would certainly be possible to use the existing ROM and switch it in and out as needed; that would presumably give you some extra RAM, but at the cost of speed and complexity, so it's probably more practical to just build a 'normal' high memory CP/M BIOS using those (relocated) routines plus any needed new ones. IIRC that's the approach we took way back then.
As to the all-RAM mode, it should be fairly easy to accomplish even without a full REX. It's not difficult to put RAM in the option ROM area which you could switch into the main memory map; software exists to move data back and forth. I'll have to dig around and see if I can find the WIP from back then. m ----- Original Message ----- From: "Jonathan Yuen" <[email protected]> To: <[email protected]> Sent: Thursday, June 08, 2017 2:30 PM Subject: Re: [M100] 100/102/200 with CP/M? Hi All, Just talking from memory (and fond memories of ZCPR) I was wondering what the REX all-RAM mode was. Did it still need the ROM calls to work? If not, where were the routines for the console i/o? I've been toying with ordering the cards to see if I could make a REX but there are still a few months to go before retirement.... Of course, an 8085 isn't a z80 but it's certainly worth playing with! Jonathan [email protected] ________________________________________ Från: M100 [[email protected]] för Mike Stein [[email protected]] Skickat: den 8 juni 2017 18:11 Till: [email protected] Ämne: Re: [M100] 100/102/200 with CP/M? As John says, there was some work done a while back but interest seems to have waned, just waiting for someone like you to remotivate everyone ;-) Steve's REX module has an all-RAM mode and IIRC it got as far as having console I/O working. There are challenges related to the M100's memory map; the M100's ROM 'BIOS' occupies the lower 32K (where CP/M needs RAM) and many of the system variables are located in the upper 2 or 3K. Also, there's the issue of file storage; not everyone has a TPDD or NADSbox, and having to be tethered to a PC would make it a fairly useless proposition. But recent work by Kurt et al using a smartphone opens up some new possibilities... m ----- Original Message ----- From: Scott Lawrence<mailto:[email protected]> To: Model 100 Discussion<mailto:[email protected]> Sent: Thursday, June 08, 2017 11:08 AM Subject: [M100] 100/102/200 with CP/M? Has there ever been a port of CP/M for the 100/102/200 line? Or, the other way around; Has anyone made modifications to their 100/102/200 to have a compatible architecture for CP/M? Just thinking that the form-factor would be totally awesome as a CP/M machine. -s -- Scott Lawrence [email protected]<mailto:[email protected]>
