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275 lines
4.7 KiB
275 lines
4.7 KiB
3 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<HTML
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><HEAD
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><TITLE
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>Bochs's CMOS map</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
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REL="HOME"
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TITLE="Bochs Developers Guide"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="About the code"
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HREF="about-the-code.html"><LINK
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REL="PREVIOUS"
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TITLE="timers"
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HREF="timers.html"><LINK
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REL="NEXT"
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TITLE="Sound Blaster 16 Emulation"
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HREF="sb16-emulation-basics.html"></HEAD
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><BODY
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CLASS="SECTION"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#840084"
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ALINK="#0000FF"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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SUMMARY="Header navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Bochs Developers Guide</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="timers.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 2. About the code</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="sb16-emulation-basics.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECTION"
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><H1
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CLASS="SECTION"
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><A
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NAME="CMOS-MAP"
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>2.7. Bochs's CMOS map</A
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></H1
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><P
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>In addition to the default CMOS RAM layout, the Bochs BIOS uses some additional
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registers for harddisk parameters and the boot sequence. The following table
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shows all CMOS registers and their meaning.</P
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><P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>Legend:
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S - set by the emulator (Bochs)
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B - set by the bios
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U - unused by the bios
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LOC NOTES MEANING
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0x00 S rtc seconds
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0x01 B second alarm
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0x02 S rtc minutes
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0x03 B minute alarm
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0x04 S rtc hours
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0x05 B hour alarm
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0x06 S,U day of week
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0x07 S,B date of month
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0x08 S,B month
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0x09 S,B year
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0x0a S,B status register A
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0x0b S,B status register B
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0x0c S status register C
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0x0d S status register D
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0x0f S shutdown status
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values:
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0x00: normal startup
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0x09: normal
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0x0d+: normal
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0x05: eoi ?
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else: unimpl
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0x10 S fd drive type (2 nibbles: high=fd0, low=fd1)
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values:
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1: 360K 5.25"
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2: 1.2MB 5.25"
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3: 720K 3.5"
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4: 1.44MB 3.5"
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5: 2.88MB 3.5"
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!0x11 configuration bits!!
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0x12 S how many disks first (hd type)
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!0x13 advanced configuration bits!!
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0x14 S,U equipment byte (?)
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bits where what
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7-6 floppy.cc
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5-4 vga.cc 0 = vga
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2 keyboard.cc 1 = enabled
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0 floppy.cc
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0x15 S,U base memory - low
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0x16 S,U base memory - high
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0x17 S,U extended memory in k - low
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0x18 S,U extended memory in k - high
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0x19 S hd0: extended type
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0x1a S hd1: extended type
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0x1b S,U hd0:cylinders - low
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0x1c S,U hd0:cylinders - high
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0x1d S,U hd0:heads
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0x1e S,U hd0:write pre-comp - low
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0x1f S,U hd0:write pre-comp - high
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0x20 S,U hd0:retries/bad_map/heads>8
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0x21 S,U hd0:landing zone - low
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0x22 S,U hd0:landing zone - high
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0x23 S,U hd0:sectors per track
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0x24 S,U hd1:cylinders - low
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0x25 S,U hd1:cylinders - high
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0x26 S,U hd1:heads
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0x27 S,U hd1:write pre-comp - low
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0x28 S,U hd1:write pre-comp - high
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0x29 S,U hd1:retries/bad_map/heads>8
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0x2a S,U hd1:landing zone - low
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0x2b S,U hd1:landing zone - high
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0x2c S,U hd1:sectors per track
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0x2d S boot from (bit5: 0:fd, 1:hd)
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0x2e S,U standard cmos checksum (0x10->0x2d) - high
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0x2f S,U standard cmos checksum (0x10->0x2d) - low
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0x30 S extended memory in k - low
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0x31 S extended memory in k - high
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0x32 S rtc century
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0x34 S extended memory in 64k - low
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0x35 S extended memory in 64k - high
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0x37 S ps/2 rtc century (copy of 0x32, needed for winxp)
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0x38 S eltorito boot sequence + boot signature check
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bits
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0 floppy boot signature check (1: disabled, 0: enabled)
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7-4 boot drive #3 (0: unused, 1: fd, 2: hd, 3:cd, else: fd)
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0x39 S ata translation policy - ata0 + ata1
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bits
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1-0 ata0-master (0: none, 1: LBA, 2: LARGE, 3: R-ECHS)
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3-2 ata0-slave
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5-4 ata1-master
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7-6 ata1-slave
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0x3a S ata translation policy - ata2 + ata3 (see above)
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0x3d S eltorito boot sequence (see above)
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bits
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3-0 boot drive #1
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7-4 boot drive #2</PRE
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></TD
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></TR
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></TABLE
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></P
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></DIV
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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SUMMARY="Footer navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="timers.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="index.html"
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ACCESSKEY="H"
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>Home</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><A
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HREF="sb16-emulation-basics.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>timers</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="about-the-code.html"
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ACCESSKEY="U"
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>Up</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>Sound Blaster 16 Emulation</TD
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></TR
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></TABLE
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></DIV
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></BODY
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></HTML
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>
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