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Added a workaround for umk3059gre and umk3137b5gre.

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It's a hack, but a well-understood and clearly documented one.
Maybe smf can fix it for real in the distant future.
This commit is contained in:
Aaron Giles 2008-01-08 09:26:12 +00:00
parent 6f0b1f3e0f
commit c846ce37d9
1 changed files with 29 additions and 0 deletions
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29
src/mame/machine/midwunit.c
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@ -400,6 +400,33 @@ static void init_wunit_generic(void)
/********************** Mortal Kombat 3 **********************/
static UINT16 *umk3_palette;
static WRITE16_HANDLER( umk3_palette_hack_w )
{
/*
UMK3 uses a circular buffer to hold pending palette changes; the buffer holds 17 entries
total, and the buffer is processed/cleared during the video interrupt. Most of the time,
17 entries is enough. However, when characters are unlocked, or a number of characters are
being displayed, the circular buffer sometimes wraps, losing the first 17 palette changes.
This bug manifests itself on a real PCB, but only rarely; whereas in MAME, it manifests
itself very frequently. This is due to the fact that the instruction timing for the TMS34010
is optimistic and assumes that the instruction cache is always fully populated. Without
full cache level emulation of the chip, there is no hope of fixing this issue without a
hack.
Thus, the hack. To slow down the CPU when it is adding palette entries to the list, we
install this write handler on the memory locations where the start/end circular buffer
pointers live. Each time they are written to, we penalize the main CPU a number of cycles.
Although not realistic, this is sufficient to reduce the frequency of incorrect colors
without significantly impacting the rest of the system.
*/
COMBINE_DATA(&umk3_palette[offset]);
activecpu_adjust_icount(-100);
/* printf("in=%04X%04X out=%04X%04X\n", umk3_palette[3], umk3_palette[2], umk3_palette[1], umk3_palette[0]); */
}
static void init_mk3_common(void)
{
/* common init */
@ -427,11 +454,13 @@ DRIVER_INIT( mk3r10 )
DRIVER_INIT( umk3 )
{
init_mk3_common();
umk3_palette = memory_install_write16_handler(0, ADDRESS_SPACE_PROGRAM, 0x0106a060, 0x0106a09f, 0, 0, umk3_palette_hack_w);
}
DRIVER_INIT( umk3r11 )
{
init_mk3_common();
umk3_palette = memory_install_write16_handler(0, ADDRESS_SPACE_PROGRAM, 0x0106a060, 0x0106a09f, 0, 0, umk3_palette_hack_w);
}