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Memory/A20: Remove "fast" remapping trick used by DOSBox SVN
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@joncampbell123
joncampbell123 committed Feb 14, 2018
1 parent 7b17c09 commit c74424c
Showing 1 changed file with 3 additions and 48 deletions.
51 changes: 3 additions & 48 deletions src/hardware/memory.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,6 @@ class MEM_callout_vector : public std::vector<MEM_CalloutObject> {
static MEM_callout_vector MEM_callouts[MEM_callouts_max];

bool a20_guest_changeable = true;
bool a20_full_masking = false;
bool a20_fake_changeable = false;

bool enable_port92 = true;
Expand Down Expand Up @@ -1068,11 +1067,7 @@ void MEM_A20_Enable(bool enabled) {

LOG(LOG_MISC,LOG_DEBUG)("MEM_A20_Enable(%u)",enabled?1:0);

if (!a20_full_masking) {
Bitu phys_base=memory.a20.enabled ? (1024/4) : 0;
for (Bitu i=0;i<16;i++) PAGING_MapPage((1024/4)+i,phys_base+i);
}
else if (!a20_fake_changeable) {
if (!a20_fake_changeable) {
if (memory.a20.enabled) memory.mem_alias_pagemask_active |= 0x100;
else memory.mem_alias_pagemask_active &= ~0x100;
PAGING_ClearTLB();
Expand Down Expand Up @@ -1452,26 +1447,6 @@ HostPt GetMemBase(void) { return MemBase; }

extern bool mainline_compatible_mapping;

static void RAM_remap_64KBat1MB_A20fast(bool enable/*if set, we're transitioning to fast remap, else to full mask*/) {
PageHandler *newp;
Bitu c=0;

/* undo the fast remap at 1MB */
for (Bitu i=0;i<16;i++) PAGING_MapPage((1024/4)+i,(1024/4)+i);

/* run through the page array, change ram_handler to ram_alias_handler
* (or the other way depending on enable) */
newp = (PageHandler*)(&ram_page_handler);
for (Bitu i=0;i < memory.reported_pages;i++) {
if (memory.phandlers[i] != newp) {
memory.phandlers[i] = newp;
c++;
}
}

LOG_MSG("A20gate mode change: %u pages modified (fast enable=%d)\n",(int)c,(int)enable);
}

class REDOS : public Program {
public:
void Run(void) {
Expand All @@ -1494,49 +1469,37 @@ class A20GATE : public Program {
MEM_A20_Enable(true);

if (!strncasecmp(x,"off_fake",8)) {
if (!a20_full_masking) RAM_remap_64KBat1MB_A20fast(false);
a20_full_masking = true;
MEM_A20_Enable(false);
a20_guest_changeable = false;
a20_fake_changeable = true;
WriteOut("A20 gate now off_fake mode\n");
}
else if (!strncasecmp(x,"off",3)) {
if (!a20_full_masking) RAM_remap_64KBat1MB_A20fast(false);
a20_full_masking = true;
MEM_A20_Enable(false);
a20_guest_changeable = false;
a20_fake_changeable = false;
WriteOut("A20 gate now off mode\n");
}
else if (!strncasecmp(x,"on_fake",7)) {
if (!a20_full_masking) RAM_remap_64KBat1MB_A20fast(false);
a20_full_masking = true;
MEM_A20_Enable(true);
a20_guest_changeable = false;
a20_fake_changeable = true;
WriteOut("A20 gate now on_fake mode\n");
}
else if (!strncasecmp(x,"on",2)) {
if (!a20_full_masking) RAM_remap_64KBat1MB_A20fast(false);
a20_full_masking = true;
MEM_A20_Enable(true);
a20_guest_changeable = false;
a20_fake_changeable = false;
WriteOut("A20 gate now on mode\n");
}
else if (!strncasecmp(x,"mask",4)) {
if (!a20_full_masking) RAM_remap_64KBat1MB_A20fast(false);
a20_full_masking = true;
MEM_A20_Enable(false);
a20_guest_changeable = true;
a20_fake_changeable = false;
memory.a20.enabled = 0;
WriteOut("A20 gate now mask mode\n");
}
else if (!strncasecmp(x,"fast",4)) {
if (!a20_full_masking) RAM_remap_64KBat1MB_A20fast(true);
a20_full_masking = false;
MEM_A20_Enable(false);
a20_guest_changeable = true;
a20_fake_changeable = false;
Expand Down Expand Up @@ -1600,7 +1563,7 @@ void Init_AddressLimitAndGateMask() {

/* update alias pagemask according to A20 gate */
memory.mem_alias_pagemask_active = memory.mem_alias_pagemask;
if (a20_fake_changeable && a20_full_masking && !memory.a20.enabled)
if (a20_fake_changeable && !memory.a20.enabled)
memory.mem_alias_pagemask_active &= ~0x100;

/* log */
Expand Down Expand Up @@ -1761,7 +1724,6 @@ void A20Gate_OverrideOn(Section *sec) {
memory.a20.enabled = 1;
a20_fake_changeable = false;
a20_guest_changeable = true;
a20_full_masking = true;
}

/* this is called after BIOS boot. the BIOS needs the A20 gate ON to boot properly on 386 or higher! */
Expand All @@ -1771,45 +1733,38 @@ void A20Gate_TakeUserSetting(Section *sec) {
memory.a20.enabled = 0;
a20_fake_changeable = false;
a20_guest_changeable = true;
a20_full_masking = false;

// TODO: A20 gate control should also be handled by a motherboard init routine
std::string ss = section->Get_string("a20");
if (ss == "mask" || ss == "") {
LOG(LOG_MISC,LOG_DEBUG)("A20: masking emulation");
a20_guest_changeable = true;
a20_full_masking = true;
}
else if (ss == "on") {
LOG(LOG_MISC,LOG_DEBUG)("A20: locked on");
a20_guest_changeable = false;
a20_full_masking = true;
memory.a20.enabled = 1;
}
else if (ss == "on_fake") {
LOG(LOG_MISC,LOG_DEBUG)("A20: locked on (but will fake control bit)");
a20_guest_changeable = false;
a20_fake_changeable = true;
a20_full_masking = true;
memory.a20.enabled = 1;
}
else if (ss == "off") {
LOG(LOG_MISC,LOG_DEBUG)("A20: locked off");
a20_guest_changeable = false;
a20_full_masking = true;
memory.a20.enabled = 0;
}
else if (ss == "off_fake") {
LOG(LOG_MISC,LOG_DEBUG)("A20: locked off (but will fake control bit)");
a20_guest_changeable = false;
a20_fake_changeable = true;
a20_full_masking = true;
memory.a20.enabled = 0;
}
else { /* "" or "fast" */
LOG(LOG_MISC,LOG_DEBUG)("A20: fast remapping (64KB+1MB) DOSBox style");
LOG(LOG_MISC,LOG_DEBUG)("A20: masking emulation (fast mode no longer supported)");
a20_guest_changeable = true;
a20_full_masking = false;
}
}

Expand Down

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