ch62.htm

linux-unix130.linux.and.unix.ebooks130 linux and unix ebookslinuxLearning Linux - Collection of 12 E

		<TD ALIGN="LEFT"><I>Meaning</I></TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>dosbanner</TT></TD>

		<TD ALIGN="LEFT"><TT>&quot;on&quot;</TT> or <TT>&quot;off&quot;</TT></TD>

		<TD ALIGN="LEFT">Turns on/off welcome banner when booting DOSemu.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>mathco</TT></TD>

		<TD ALIGN="LEFT"><TT>&quot;on&quot;</TT> or <TT>&quot;off&quot;</TT></TD>

		<TD ALIGN="LEFT">Tells MS-DOS if a coprocessor is available. Because Linux already emulates a math

			coprocessor, set this parameter to <TT>&quot;on&quot;</TT>.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>dpmi</TT></TD>

		<TD ALIGN="LEFT"><TT>&quot;on&quot;</TT> or <TT>&quot;off&quot;</TT></TD>

		<TD ALIGN="LEFT">Turns on DPMI support. This is a bit unstable, so use with caution.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>FastFloppy</TT></TD>

		<TD ALIGN="LEFT">Number</TD>

		<TD ALIGN="LEFT">Turns on higher-speed floppy access. Use with caution.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>speaker</TT></TD>

		<TD ALIGN="LEFT"><TT>&quot;off&quot;</TT>, <TT>&quot;native&quot;</TT>,</TD>

		<TD ALIGN="LEFT">Turns on access to speaker by</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"></TD>

		<TD ALIGN="LEFT"><TT>&quot;emulated&quot;</TT></TD>

		<TD ALIGN="LEFT">direct access, <TT>emulated</TT> or by a speaker emulation mode.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>EmuSys</TT></TD>

		<TD ALIGN="LEFT">File extension</TD>

		<TD ALIGN="LEFT">Uses an alternative <TT>config.sys</TT> file with this file extension. A good value

			might be <TT>&quot;EMU&quot;</TT>. Alternative to</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT">DOS 6 boot menus.</TD>

		<TD ALIGN="LEFT"></TD>

		<TD ALIGN="LEFT"></TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>EmuBat</TT></TD>

		<TD ALIGN="LEFT">File extension</TD>

		<TD ALIGN="LEFT">Uses an alternative <TT>autoexec.bat</TT> file with this file extension. Similar

			to <TT>EmuSYS</TT>.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>cpu</TT></TD>

		<TD ALIGN="LEFT"><TT>80286</TT>, <TT>80386</TT></TD>

		<TD ALIGN="LEFT">CPU type to emulate. Because you won't fool all programs, use what you really have.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>ipxsupport</TT></TD>

		<TD ALIGN="LEFT"><TT>&quot;on&quot;</TT> or <TT>&quot;off&quot;</TT></TD>

		<TD ALIGN="LEFT">Allows IPX access through the Linux kernel.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>xms</TT></TD>

		<TD ALIGN="LEFT">Size in kilobytes</TD>

		<TD ALIGN="LEFT">Amount of XMS memory to make</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"></TD>

		<TD ALIGN="LEFT">or <TT>&quot;off&quot;</TT></TD>

		<TD ALIGN="LEFT">available.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>ems</TT></TD>

		<TD ALIGN="LEFT">Size in kilobytes</TD>

		<TD ALIGN="LEFT">Amount of EMS memory to make</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"></TD>

		<TD ALIGN="LEFT">or <TT>&quot;off&quot;</TT></TD>

		<TD ALIGN="LEFT">available.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>Hogthreshold</TT></TD>

		<TD ALIGN="LEFT">Number</TD>

		<TD ALIGN="LEFT">The higher the number, the longer DOS can &quot;hog&quot; the CPU waiting for a keystroke.

			An initial setting of <TT>5000</TT> is a good starting point. Set to <TT>0</TT> to

			turn off hog detection.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>bootB</TT></TD>

		<TD ALIGN="LEFT"></TD>

		<TD ALIGN="LEFT">Specifies that DOS is to boot from the floppy configured as B.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>ports{ }</TT></TD>

		<TD ALIGN="LEFT"></TD>

		<TD ALIGN="LEFT">Allows DOSemu access to specific hardware ports. List the hex values of hardware

			ports desired.</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>mouse</TT></TD>

		<TD ALIGN="LEFT">Type of mouse</TD>

		<TD ALIGN="LEFT">Microsoft, Logitech, mmseries,</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"></TD>

		<TD ALIGN="LEFT">you have</TD>

		<TD ALIGN="LEFT">Mouseman, Hitachi, busmouse, Mousesystems, and PS2 are supported.</TD>

	</TR>

</TABLE>



</CENTER>

<CENTER>

<H3><A NAME="Heading27<FONT COLOR="#000077">Runtime Options of DOSemu</FONT></H3>

</CENTER>

<P>Table 62.3 shows the command options supported on the DOSemu command line. Options

specified here override conflicting parameters specified in the <TT>dosemu.conf</TT>

file. A few other options are available, but those are either intended for development

use or are not completely supported yet. Use the <TT>-?</TT> option to get a complete

list of the command options.</P>

<CENTER>

<P><FONT SIZE="4"><B>Table 62.3. DOSemu command-line options. </B></FONT>

<TABLE BORDER="0">

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><I>Option</I></TD>

		<TD ALIGN="LEFT"><I>Meaning</I></TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-A</TT></TD>

		<TD ALIGN="LEFT">Boot from floppy A</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-C</TT></TD>

		<TD ALIGN="LEFT">Boot from hard drive C</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-D</TT></TD>

		<TD ALIGN="LEFT">Set debug options</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-F</TT></TD>

		<TD ALIGN="LEFT">Number of floppy disks to use from <TT>dosemu.conf</TT> (1-4)</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-H</TT></TD>

		<TD ALIGN="LEFT">Number of hard disks to use from <TT>dosemu.conf</TT> (1 or 2)</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-P</TT></TD>

		<TD ALIGN="LEFT">Copy debug information to file, same as using <TT>2&gt;</TT></TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-V</TT></TD>

		<TD ALIGN="LEFT">Turn on VGA emulation</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-c</TT></TD>

		<TD ALIGN="LEFT">Optimize video performance under virtual consoles</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-e</TT></TD>

		<TD ALIGN="LEFT">Specify the amount of EMS memory to make available</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-f</TT></TD>

		<TD ALIGN="LEFT">Flip definition of A: and B: floppy</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-k</TT></TD>

		<TD ALIGN="LEFT">Use raw keyboard console (<TT>rawkeyboard</TT> in <TT>dosemu.conf</TT>)</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-t</TT></TD>

		<TD ALIGN="LEFT">Deliver time interrupt 9</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-x</TT></TD>

		<TD ALIGN="LEFT">Specify the amount of XMS memory to make available</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-?</TT></TD>

		<TD ALIGN="LEFT">Print command summary only</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-2</TT></TD>

		<TD ALIGN="LEFT">Emulate a 286</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-3</TT></TD>

		<TD ALIGN="LEFT">Emulate a 386</TD>

	</TR>

	<TR ALIGN="LEFT" rowspan="1">

		<TD ALIGN="LEFT"><TT>-4</TT></TD>

		<TD ALIGN="LEFT">Emulate a 486</TD>

	</TR>

</TABLE>



</CENTER>

<CENTER>

<H3><A NAME="Heading28<FONT COLOR="#000077">Limitations of DOSemu</FONT></H3>

</CENTER>

<P>DOSemu is not perfect yet. Development is underway, with many known opportunities

for speed optimizations and improvements.

<CENTER>

<H4><A NAME="Heading29<FONT COLOR="#000077">Notable Software That Wont Run

Under DOSemu</FONT></H4>

</CENTER>

<P>Perhaps the most significant application that does not run under DOSemu is Windows

3.1. As with Linux in general, volunteers are working to correct this limitation.

Other software that requires DOS Protected Mode Interface (DPMI) is also likely to

cause problems. To find an up-to-date list of software that has been successfully

used under DOSemu, look for the file <TT>/doc/EMUsucess.txt</TT> in the DOSemu distribution.

<CENTER>

<H4><A NAME="Heading30<FONT COLOR="#000077">Hardware Limitations for DOSemu</FONT></H4>

</CENTER>

<P>Not all video cards are currently supported under DOSemu. More popular cards are

supported simply because developers are more likely to have them. Some nontypical

hardware is reported to work under DOSemu with some patches.</P>

<P>Some sound cards are problematic under DOSemu. They have the potential to perform

DMA (direct memory access) to memory the Linux kernel had allocated elsewhere. A

generic sound-card interface that interacts with the kernel's built-in sound card

support would solve this problem.

<CENTER>

<H4><A NAME="Heading31<FONT COLOR="#000077">Performance Limitations</FONT></H4>

</CENTER>

<P>DOSemu runs slower than a native MS-DOS session. I have successfully run a few

older benchmark programs under DOSemu to compare the performance degradation with

that of native MS-DOS. Benchmark results are not a perfect measure, but they do demonstrate

potential performance in some distinct areas. I measured three different areas: CPU

performance, disk performance, and video performance, each of which produced strangely

different results. CPU Performance DOSemu's raw CPU speed depends on what else is

happening under Linux. With an otherwise idle Linux box, DOSemu's compute speed is

close to that of a native MS-DOS session. The Landmark Version 2.0 and PC-Bench Version

5.6 show similar performance, with perhaps a 10 to 20 percent performance penalty

under DOSemu for the instruction mix, CPU, and FPU measurements. Disk Performance

Determining the disk-speed degradation under DOSemu proved to be difficult. In some

cases there was a performance decrease, and in others a performance increase. This

discrepancy seems directly related to the quality of support of the controller and

disk drive from the underlying Linux kernel, as well as the built-in caching provided

by Linux.</P>

<P>Linux runs as a pure 32-bit operating system and handles I/O operations to disk

controllers in bait mode. This, combined with much better SCSI support, can lead

to equal or better disk benchmark numbers under DOSemu than under native DOS. Not

all disks are as fast under DOSemu, with performance degradation ranging from small

to huge. As with CPU speed, disk speed depends on what other Linux tasks are doing.

Video Performance Video support is Linux's Achilles' heel. Text performance is much

slower when DOSemu is not being run under a virtual console. Under a virtual console,

benchmarked text speed approaches that achieved with native MS-DOS. When you are

using real-world applications, the text speed is dramatically slower, with an observed

speed as low as 20 percent of the speed under native MS-DOS. Graphics speed is even

worse.

<CENTER>

<H3><A NAME="Heading32<FONT COLOR="#000077">Mouse Support</FONT></H3>