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.