Labels:text | screenshot | parallel | document | black and white | number | line | font | receipt OCR: B.8 - Memory Map M M T F T T e T 9 e g 0 1 0 S T 0 e 3 0 Location(s) Size Type Meaning 0x00000426 LONG RAM resvalid': If this location contains the magic number $31415926 then the system will jump through resvector (below) on a system reset. 0x0000042A LONG RAM resvector. If the magic number in resvalid' is set properly, this vector will be jumped through on a system reset with the return address placed in AB. 0x0000042E LONG RAM phystop: Physical top of ST compatible RAM. 0x00000432 LONG RAM _membot: This value points to the lowest memory location available for the system heap. This value is used to initialize GEMDOS free memory. 0x00000436 LONG RAM _memtop: This value points to the highest memory location available for the system heap. This value is used to initialize GEMDOS free memory. 0x0000043A LONG RAM memval 2: This value will equal $237698AA if coldstart was successful. See memvalid' ($420). 0x0000043E WORD RAM Hoch: This variable should be set to non-zero prior to accessing the DMA registers to prevent the system or other processes from attempting DMA concurrently. 0x00000440 WORD RAM seekrate: This variable sets the floppy drive seek rate for both floppy drives as follows: Value 0 Seek Rate 8 ms 1 12 ms 2 2 ms 3 3 ms (default) 0x00000442 WORD RAM timr_m's: This value indicates the time between system timer ticks in milliseconds. Current machines have the value of 20 (0x14) equating to 50 timer updates per second. This value is returned by the BIOS function Tickcal() and is placed on the stack prior to jumping through the timer handoff vector ($400). 0x00000444 WORD RAM _fverify: When non-zero, all floppy writes are verified, otherwise, no verification is done. 0x00000446 WORD RAM _bootd'ev: This value represents the device from which the system was booted (0 = A :, 1 = B :, etc.) 0x00000448 WORD RAM palmode: A value of0 indicates that NTSC video is being used, otherwise, PAL is being is used. 0x0000044A WORD RAM d'e/shamd': This value indicates the default video shifter mode.
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