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Add some random woz jitter (#942)

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Improve WOZ support for WL and LOA (#930)
- After T$00,S$00 (for certain 4&4 encodings) randomly skip 1 bit-cell
- Remove the previous fix for WL/LOA which was affecting other titles
This commit is contained in:
TomCh 2021-04-10 15:31:54 +01:00 committed by GitHub
parent a37d0b078f
commit b5726aae7d
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 60 additions and 8 deletions
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60
source/Disk.cpp
View File

@ -54,6 +54,9 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
// . if false && I/O ReadWrite($C0EC) && drive is spinning, then advance the track buffer's nibble index (to simulate spinning).
// Also m_enhanceDisk is persisted to the save-state, so it's an attribute of the DiskII interface card.
// NB. Non-standard 4&4, with Vol=0x00 and Chk=0x00 (only a few match, eg. Wasteland, Legacy of the Ancients, Planetfall, Border Zone & Wizardry). [*1]
const BYTE Disk2InterfaceCard::m_T00S00Pattern[] = {0xD5,0xAA,0x96,0xAA,0xAA,0xAA,0xAA,0xAA,0xAA,0xAA,0xAA,0xDE};
Disk2InterfaceCard::Disk2InterfaceCard(UINT slot) :
Card(CT_Disk2),
m_slot(slot)
@ -1043,6 +1046,9 @@ void Disk2InterfaceCard::ResetLogicStateSequencer(void)
m_resetSequencer = true;
m_writeStarted = false;
m_dbgLatchDelayedCnt = 0;
m_T00S00PatternIdx = 0;
m_foundT00S00Pattern = false;
}
UINT Disk2InterfaceCard::GetBitCellDelta(const ULONG uExecutedCycles)
@ -1118,6 +1124,48 @@ __forceinline void Disk2InterfaceCard::IncBitStream(FloppyDisk& floppy)
}
}
void Disk2InterfaceCard::PreJitterCheck(int phase, BYTE latch)
{
if (phase != 0 || (latch & 0x80) == 0)
return;
if (latch == m_T00S00Pattern[m_T00S00PatternIdx])
{
m_T00S00PatternIdx++;
if (m_T00S00PatternIdx == sizeof(m_T00S00Pattern))
m_foundT00S00Pattern = true; // 6502 code has just read latch nibbles for T$00,S$00 address prologue
}
else
{
m_T00S00PatternIdx = 0;
}
}
// GH#930: After T$00,S$00 randomly skip 1 bit-cell.
// . PreJitterCheck() condition met && skipped a big number of bit-cells.
// . Fix is just for 'Wasteland' and 'Legacy of the Ancients' (but shouldn't interfere with any other woz images).
// . NB. This is likely to be the transition from DiskII firmware ($C6xx) to user-code ($801),
// so skipping 1 bit-cell here shouldn't matter.
// . And (see comment [*1]) the T00S00 pattern only matches a handful of titles.
void Disk2InterfaceCard::AddJitter(int phase, FloppyDisk& floppy)
{
if (phase == 0 && m_foundT00S00Pattern)
{
if (rand() < RAND_THRESHOLD(1, 10))
{
LogOutput("Disk: T$00 jitter - slip 1 bitcell (PC=%04X)\n", regs.pc);
IncBitStream(floppy);
}
else
{
LogOutput("Disk: T$00 jitter - *** SKIP *** (PC=%04X)\n", regs.pc);
}
}
m_T00S00PatternIdx = 0;
m_foundT00S00Pattern = false;
}
void __stdcall Disk2InterfaceCard::DataLatchReadWriteWOZ(WORD pc, WORD addr, BYTE bWrite, ULONG uExecutedCycles)
{
_ASSERT(m_seqFunc.function != dataShiftWrite);
@ -1161,6 +1209,8 @@ void __stdcall Disk2InterfaceCard::DataLatchReadWriteWOZ(WORD pc, WORD addr, BYT
m_latchDelay = 0;
drive.m_headWindow = 0;
AddJitter(drive.m_phase, floppy); // Only call when skipping a big number of bit-cells (ie. >significantBitCells)
}
if (!bWrite)
@ -1173,6 +1223,8 @@ void __stdcall Disk2InterfaceCard::DataLatchReadWriteWOZ(WORD pc, WORD addr, BYT
}
DataLatchReadWOZ(pc, addr, bitCellRemainder);
PreJitterCheck(drive.m_phase, m_floppyLatch); // Pre: m_floppyLatch just updated
}
else
{
@ -1198,7 +1250,6 @@ void Disk2InterfaceCard::DataLatchReadWOZ(WORD pc, WORD addr, UINT bitCellRemain
#if _DEBUG
static int dbgWOZ = 0;
if (dbgWOZ)
{
dbgWOZ = 0;
@ -1206,9 +1257,6 @@ void Disk2InterfaceCard::DataLatchReadWOZ(WORD pc, WORD addr, UINT bitCellRemain
}
#endif
// Only extraCycles of 2 & 3 can hold the latch for another bitCell period, eg. m_latchDelay: 3->5 or 7->9
UINT extraLatchDelay = ((UINT)floppy.m_extraCycles >= 2) ? 2 : 0; // GH#733 (0,1->0; 2,3->2)
for (UINT i = 0; i < bitCellRemainder; i++)
{
BYTE n = floppy.m_trackimage[floppy.m_byte];
@ -1233,10 +1281,6 @@ void Disk2InterfaceCard::DataLatchReadWOZ(WORD pc, WORD addr, UINT bitCellRemain
if (m_latchDelay)
{
if (i == bitCellRemainder-1) // On last bitCell
m_latchDelay += extraLatchDelay; // +0 or +2
extraLatchDelay = 0; // and always clear (even when not last bitCell)
m_latchDelay -= 4;
if (m_latchDelay < 0)
m_latchDelay = 0;

8
source/Disk.h
View File

@ -207,6 +207,9 @@ private:
void InitFirmware(LPBYTE pCxRomPeripheral);
void UpdateLatchForEmptyDrive(FloppyDrive* pDrive);
void PreJitterCheck(int phase, BYTE latch);
void AddJitter(int phase, FloppyDisk& floppy);
void SaveSnapshotFloppy(YamlSaveHelper& yamlSaveHelper, UINT unit);
void SaveSnapshotDriveUnit(YamlSaveHelper& yamlSaveHelper, UINT unit);
bool LoadSnapshotFloppy(YamlLoadHelper& yamlLoadHelper, UINT unit, UINT version, std::vector<BYTE>& track);
@ -274,6 +277,11 @@ private:
SEQUENCER_FUNCTION m_seqFunc;
UINT m_dbgLatchDelayedCnt;
// Jitter (GH#930)
static const BYTE m_T00S00Pattern[];
UINT m_T00S00PatternIdx;
bool m_foundT00S00Pattern;
// Debug:
#if LOG_DISK_NIBBLES_USE_RUNTIME_VAR
bool m_bLogDisk_NibblesRW; // From VS Debugger, change this to true/false during runtime for precise nibble logging