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-rw-r--r--src/mess/machine/dccons.c34
1 files changed, 17 insertions, 17 deletions
diff --git a/src/mess/machine/dccons.c b/src/mess/machine/dccons.c
index 67137a5103d..48f4bd372a6 100644
--- a/src/mess/machine/dccons.c
+++ b/src/mess/machine/dccons.c
@@ -162,28 +162,28 @@ WRITE32_MEMBER(dc_cons_state::dc_mess_g1_ctrl_w )
break;
/*
- The following register is involved in BIOS checksum protection system.
- current understanding of its functioning based on several hardware tests:
+ The following register is involved in BIOS checksum protection system.
+ current understanding of its functioning based on several hardware tests:
- after power on system is in "protected state":
- - access to G1 ATA register area (5F70XX) is locked, ie GD-ROM in Dreamcast or cartridge/DIMM in arcade systems is not accessible;
- - *any* data readed via G1 data bus (ie BIOS) is summed internally by chipset;
- - write to GD_UNLOCK (5F74E4) register set "last address" of checksummed area;
+ after power on system is in "protected state":
+ - access to G1 ATA register area (5F70XX) is locked, ie GD-ROM in Dreamcast or cartridge/DIMM in arcade systems is not accessible;
+ - *any* data readed via G1 data bus (ie BIOS) is summed internally by chipset;
+ - write to GD_UNLOCK (5F74E4) register set "last address" of checksummed area;
- then readed address matches with "last address" - calculated summ compared with some hardcoded value
- if values match - system becomes in "unlocked state":
- - G1 ATA registers unlocked;
- - by write to GD_UNLOCK register system can be switched back to "protected state"
+ then readed address matches with "last address" - calculated summ compared with some hardcoded value
+ if values match - system becomes in "unlocked state":
+ - G1 ATA registers unlocked;
+ - by write to GD_UNLOCK register system can be switched back to "protected state"
- if values doesn't match - system switch to "locked state":
- - similar to protected, but data summing seems not performed anymore,
- at least write to GD_UNLOCK and "pumping" through G1 bus data chunk with valid checksumm have no effect;
- - the only exit from this state - power off/on or reset;
+ if values doesn't match - system switch to "locked state":
+ - similar to protected, but data summing seems not performed anymore,
+ at least write to GD_UNLOCK and "pumping" through G1 bus data chunk with valid checksumm have no effect;
+ - the only exit from this state - power off/on or reset;
- actual checksum algorithm is unknown, but its supposed to be simple and weak,
- known few modded BIOSes which succesfully passes this CRC check, because of good luck
+ actual checksum algorithm is unknown, but its supposed to be simple and weak,
+ known few modded BIOSes which succesfully passes this CRC check, because of good luck
- all described above works the same way in all HOLLY/CLX2-based systems - Dreamcast, Naomi 1/2, Atomiswave, SystemSP
+ all described above works the same way in all HOLLY/CLX2-based systems - Dreamcast, Naomi 1/2, Atomiswave, SystemSP
*/
case GD_UNLOCK:
if (data==0 || data==0x001fffff || data==0x42fe)