1.1 --- a/tools/firmware/vgabios/clext.c	Fri Oct 26 10:33:12 2007 +0100
     1.2 +++ b/tools/firmware/vgabios/clext.c	Fri Oct 26 10:41:07 2007 +0100
     1.3 @@ -1489,14 +1489,26 @@ cirrus_clear_vram_1:
     1.4    mov dx, #0x3ce
     1.5    out dx, ax
     1.6    push ax
     1.7 -  mov cx, #0xa000
     1.8 -  mov es, cx
     1.9 -  xor di, di
    1.10 +
    1.11 +;; Windows Vista appears to be emulating this sequence as part of changing 
    1.12 +;; screen resolution, but it generates 4096 writes per iteration.
    1.13 +;; Instead, use a magic register sequence to write the whole bank.
    1.14 +;;mov cx, #0xa000
    1.15 +;;mov es, cx
    1.16 +;;xor di, di
    1.17 +;;mov ax, si
    1.18 +;;mov cx, #8192
    1.19 +;;cld
    1.20 +;;rep
    1.21 +;;    stosw
    1.22    mov ax, si
    1.23 -  mov cx, #8192
    1.24 -  cld
    1.25 -  rep
    1.26 -      stosw
    1.27 +  shl ax, #8
    1.28 +  mov al, #0xfe
    1.29 +  out dx, ax	;; Low byte of value to be written to the bank
    1.30 +  mov ax, si
    1.31 +  mov al, #0xff  
    1.32 +  out dx, ax    ;; High byte and trigger the write
    1.33 +
    1.34    pop ax
    1.35    inc ah
    1.36    cmp ah, bl

     2.1 --- a/tools/ioemu/hw/cirrus_vga.c	Fri Oct 26 10:33:12 2007 +0100
     2.2 +++ b/tools/ioemu/hw/cirrus_vga.c	Fri Oct 26 10:41:07 2007 +0100
     2.3 @@ -294,6 +294,7 @@ void *shared_vram;
     2.4  
     2.5  static void cirrus_bitblt_reset(CirrusVGAState *s);
     2.6  static void cirrus_update_memory_access(CirrusVGAState *s);
     2.7 +static void cirrus_vga_mem_writew(void *opaque, target_phys_addr_t addr, uint32_t val);
     2.8  
     2.9  /***************************************
    2.10   *
    2.11 @@ -1497,6 +1498,17 @@ cirrus_hook_write_gr(CirrusVGAState * s,
    2.12      case 0x31:			// BLT STATUS/START
    2.13  	cirrus_write_bitblt(s, reg_value);
    2.14  	break;
    2.15 +
    2.16 +	// Extension to allow BIOS to clear 16K VRAM bank in one operation
    2.17 +    case 0xFE:
    2.18 +	s->gr[reg_index] = reg_value;  // Lower byte of value to be written
    2.19 +	break;
    2.20 +    case 0xFF: {
    2.21 +	target_phys_addr_t addr;
    2.22 +	for (addr = 0xa0000; addr < 0xa4000; addr += 2)
    2.23 +	    cirrus_vga_mem_writew(s, addr, (reg_value << 8) | s->gr[0xFE]);
    2.24 +	}
    2.25 +	break;
    2.26      default:
    2.27  #ifdef DEBUG_CIRRUS
    2.28  	printf("cirrus: outport gr_index %02x, gr_value %02x\n", reg_index,