Memotech CP/M System Sizes

Everything about Memotech CP/M and CP/M Software.
Tony Brewer
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Joined: 08 Jan 2014 20:50

Re: Memotech CP/M System Sizes

Post by Tony Brewer » 27 Apr 2018 17:21

Dave wrote:The free space pointer (FSP) reported by config.com is D588 for the 54k system and E988 for the 59K system, 1400h (~5k dec) difference, but I am not sure what the FSP actually means? Is all of the memory between 100h and the FSP available for CP/M, but BIOS, BDOS, system variables, etc., above the FSP?
I don't know what the FSP means either. From the reconstructed SDX ROM source code D400-D6FF is used for relocated Ring mailboxes and D3FF is the top of free space for BASIC. D700 is the start of the BDOS, which means the maximum RAM available for a CP/M program is 0100-D6FF. The Console Command Processor starts at CF00 (probably) and if the program does not overwrite the CCP it could exit with a RET, otherwise a jump to zero would be needed to do a warm boot and reload the CCP.

Tony Brewer
Posts: 62
Joined: 08 Jan 2014 20:50

Re: Memotech CP/M System Sizes

Post by Tony Brewer » 27 Apr 2018 17:30

E988 is close to 59K, so perhaps this is where the system size comes from. The BIOS starts at E500, with BASIC system variables at the top of RAM.

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Crazyboss
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Re: Memotech CP/M System Sizes

Post by Crazyboss » 25 May 2018 11:15

I think I read somewhere, other computer systems CP/M was the same, it clearly how high they could go in the memory. Not sure if it had something to do with the version of cp/m too ? Could it be something that the older CP/M used 0xF000 as the last useable address and the newer cp/m move that pointer to 0xFFFF?
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