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HDD: fix for slowdown during r/w block operations

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. firmware does busy-wait RMW (rol abs,x)
. the IORead then IOWrite was flipping the LED status each access, with a huge performance penalty!
This commit is contained in:
tomcw 2021-12-12 11:53:37 +00:00
parent 19aadbfb8d
commit 651b57fdae
1 changed files with 10 additions and 3 deletions
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13
source/Harddisk.cpp
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@ -556,7 +556,7 @@ BYTE __stdcall HarddiskInterfaceCard::IORead(WORD pc, WORD addr, BYTE bWrite, BY
break;
case 0x02: //write
{
pHDD->m_status_next = DISK_STATUS_WRITE;
pHDD->m_status_next = DISK_STATUS_WRITE; // or DISK_STATUS_PROT if we ever enable write-protect on HDD
bool bRes = true;
const bool bAppendBlocks = (pHDD->m_diskblock * HD_BLOCK_SIZE) >= ImageGetImageSize(pHDD->m_imagehandle);
@ -619,7 +619,7 @@ BYTE __stdcall HarddiskInterfaceCard::IORead(WORD pc, WORD addr, BYTE bWrite, BY
}
break;
case 0x03: //format
pHDD->m_status_next = DISK_STATUS_WRITE;
pHDD->m_status_next = DISK_STATUS_WRITE; // or DISK_STATUS_PROT if we ever enable write-protect on HDD
break;
}
}
@ -684,10 +684,17 @@ BYTE __stdcall HarddiskInterfaceCard::IOWrite(WORD pc, WORD addr, BYTE bWrite, B
HardDiskDrive* pHDD = &(pCard->m_hardDiskDrive[pCard->m_unitNum >> 7]); // bit7 = drive select
BYTE r = DEVICE_OK;
pHDD->m_status_next = DISK_STATUS_PROT; // TODO: FIXME: If we ever enable write-protect on HD then need to change to something else ...
switch (addr & 0xF)
{
case 0x0: // r/o: status
case 0x1: // r/o: execute
case 0x8: // r/o: legacy next-data port
// Writing to these 3 read-only registers is a no-op.
// NB. Don't change m_status_next, as UpdateLightStatus() has a huge performance cost!
// Firmware has a busy-wait loop doing "rol hd_status,x"
// - this RMW opcode does an IORead() then an IOWrite(), and the loop iterates ~100 times!
break;
case 0x2:
pCard->m_command = d;
break;