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fix UMB mapping for EMS and PCjr cases. don't assume 64KB.

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Jonathan Campbell
2015-02-15 23:15:12 -08:00
parent bdce1fcfcd
commit cbc0b743dc
1 changed files with 9 additions and 1 deletions
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10
src/dos/dos_memory.cpp
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@@ -411,7 +411,15 @@ void DOS_BuildUMBChain(bool umb_active,bool ems_active) {
/* UMBs are only possible if the machine has 1MB+64KB of RAM */
if (umb_active && (machine!=MCH_TANDY) && seg_limit >= (0x10000+0x1000-1)) {
if(ems_active || (machine == MCH_PCJR)) first_umb_size = 0x1000;
if (ems_active) {
/* we can use UMBs up to the EMS page frame */
/* FIXME: when we make the EMS page frame configurable this will need to be updated */
first_umb_size = 0xE000 - first_umb_seg;
}
else if (machine == MCH_PCJR) {
/* we can use UMBs up to where PCjr wants cartridge ROM */
first_umb_size = 0xE000 - first_umb_seg;
}
dos_infoblock.SetStartOfUMBChain(UMB_START_SEG);
dos_infoblock.SetUMBChainState(0); // UMBs not linked yet