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- update(): skip screen update if the vertical retrace is in progress

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(using 72 Hz vertical frequency). The vertial retrace phase is often used for
  vga register or memory manipulations to reduce screen flickering.
- update(): check variable vga_mem_updated before everything else
This commit is contained in:
Volker Ruppert 2003-06-10 16:26:19 +00:00
parent f7bf4817dd
commit 906b7f8d1c
1 changed files with 8 additions and 4 deletions
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12
bochs/iodev/vga.cc
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@ -1,5 +1,5 @@
/////////////////////////////////////////////////////////////////////////
// $Id: vga.cc,v 1.77 2003-06-08 16:45:24 vruppert Exp $
// $Id: vga.cc,v 1.78 2003-06-10 16:26:19 vruppert Exp $
/////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2002 MandrakeSoft S.A.
@ -1290,14 +1290,18 @@ bx_vga_c::update(void)
{
unsigned iHeight, iWidth;
/* no screen update necessary */
if (BX_VGA_THIS s.vga_mem_updated==0)
return;
/* skip screen update when the sequencer is in reset mode */
if (!BX_VGA_THIS s.sequencer.reset1 || !BX_VGA_THIS s.sequencer.reset2)
return;
if (BX_VGA_THIS s.vga_mem_updated==0) {
/* BX_DEBUG(("update(): updated=%u enabled=%u", (unsigned) BX_VGA_THIS s.vga_mem_updated, (unsigned) BX_VGA_THIS s.attribute_ctrl.video_enabled)); */
/* skip screen update if the vertical retrace is in progress
(using 72 Hz vertical frequency) */
if ((bx_pc_system.time_usec() % 13888) < 70)
return;
}
#if BX_SUPPORT_VBE
if ((BX_VGA_THIS s.vbe_enabled) && (BX_VGA_THIS s.vbe_bpp != VBE_DISPI_BPP_4))