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x68k: try to fix the gvram clear

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This commit is contained in:
cracyc 2021-09-29 21:37:17 -05:00
parent 746563cd03
commit df0333754b
1 changed files with 44 additions and 2 deletions
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46
src/mame/video/x68k_crtc.cpp
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@ -421,8 +421,50 @@ void x68k_crtc_device::crtc_w(offs_t offset, u16 data, u16 mem_mask)
m_operation = data;
if (data & 0x02) // high-speed graphic screen clear
{
for (offs_t addr = 0; addr < 0x40000; addr++)
m_gvram_write_callback(addr, 0, 0xffff);
// this is based on the docs except for the higher color depth modes which isn't
// explicitly described this way but is likely based on how the plane scroll works
// XXX: not sufficiently tested especially in hires modes
for (int page = 0; page < 4; page++)
{
if (!(m_reg[21] & (1 << page)))
continue;
uint16_t xscr = xscr_gfx(page) & 0x1ff;
uint16_t yscr = yscr_gfx(page) & 0x1ff;
uint16_t mask = ~(0xf << (page * 4));
for (int y = yscr; y < (m_height + yscr); y++)
{
if (is_1024x1024())
{
if (m_width > 256)
{
for (int x = 0; x < 512; x++)
{
uint16_t data = m_gvram_read_callback(((y * 512) + x) & 0x3ffff, 0xffff);
m_gvram_write_callback(((y * 512) + x) & 0x3ffff, data & mask, 0xffff);
}
}
else
{
for (int x = 0; x < 256; x++)
{
uint16_t data = m_gvram_read_callback(((y * 512) + x + xscr) & 0x3ffff, 0xffff);
m_gvram_write_callback(((y * 512) + x + xscr) & 0x3ffff, data & mask, 0xffff);
data = m_gvram_read_callback(((y * 512) + x + xscr + 256) & 0x3ffff, 0xffff);
m_gvram_write_callback(((y * 512) + x + xscr + 256) & 0x3ffff, data & mask, mask);
}
}
}
else
{
for (int x = 0; x < m_width; x++)
{
uint16_t data = m_gvram_read_callback(((y * 512) + x) & 0x3ffff, 0xffff);
m_gvram_write_callback(((y * 512) + x) & 0x3ffff, data & mask, 0xffff);
}
}
}
}
m_operation_end_timer->adjust(attotime::from_msec(10), 0x02); // time taken to do operation is a complete guess.
}
break;