trunk/man/gxemul.1

.\" $Id: gxemul.1,v 1.34 2005/10/11 03:53:58 debug Exp $
.\"
.\" Copyright (C) 2004-2005  Anders Gavare.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\" 
.\" 
.\" This is a minimal man page for GXemul. Process this file with
.\"     groff -man -Tascii gxemul.1    or    nroff -man gxemul.1
.\"
.Dd OCTOBER 2005
.Dt GXEMUL 1
.Os
.Sh NAME
.Nm gxemul
.Nd an experimental machine emulator
.Sh SYNOPSIS
.Nm
.Op machine, other, and general options
.Op file Ar ...
.Nm
.Op general options
.Ar @configfile
.Nm
.Op userland, other, and general options
.Ar file Op Ar args ...
.Sh DESCRIPTION
.Nm
is an experimental instruction-level machine emulator. Several
emulation modes are available. In some modes, processors and surrounding
hardware components are emulated well enough to let unmodified operating
systems (e.g. NetBSD) run as if they were running on a real machine.
.Pp
The processor architecture best emulated by GXemul is MIPS, but other
architectures are also partially emulated.
.Pp
There are three ways to invoke the emulator:
.Pp
1. When emulating a complete machine, configuration options can be entered
directly on the command line.
.Pp
2. Options can be read from a configuration file.
.Pp
3. When emulating a userland environment (syscall-only emulation, not
emulating complete machines), then the program name and its argument
should be given on the command line. (This mode doesn't really work yet.)
.Pp
The easiest way to use the emulator is to supply settings directly on the 
command line. The most important thing you need to supply is the
file argument. This is the name of a binary file (an ELF, a.out, COFF/ECOFF,
SREC, or a raw binary image) which you wish to run in the emulator. This file
might be an operating system kernel, or perhaps a ROM image file.
.Pp
If more than one filename is supplied, all files are loaded into memory, 
and the entry point (if available) is taken from the last file.
.Pp
Apart from the name of a binary file, it is also necessary to select
which specific emulation mode to use. For example, a MIPS-based machine
from DEC (a DECstation) is very different from a MIPS-based machine
from SGI. Use
.Nm
.Fl H
to get a list of available emulation modes.
.Pp
There are two exceptions to the normal invocation usage mentioned above.
The first is for DECstation emulation: if you have a bootable
DECstation harddisk or CDROM image, then just supplying the diskimage via 
the
.Fl d
option is sufficient. (The filename of the kernel can then be 
skipped, as the emulator runs the bootblocks from the diskimage directly and 
doesn't need the kernel as a separate file.)
The second is if you supply an ISO9660 CDROM disk image. You may then use 
the
.Fl j
option to indicate which file on the CDROM filesystem that should be 
loaded into emulated memory.
.Pp
Machine selection options:
.Bl -tag -width Ds
.It Fl E Ar t
Try to emulate machine type
.Ar "t".
This option is not always needed, if the
.Fl e
option uniquely selects a machine.
(Use
.Fl H
to get a list of types.)
.It Fl e Ar st
Try to emulate machine subtype
.Ar "st".
Use this together with
.Fl E .
(This option is not always needed, if a machine type has no subtypes.)
.El
.Pp
Other options:
.Bl -tag -width Ds
.It Fl A
Disable load/store alignment checks in some cases. This might give a small
increase in performance, but the emulator will not run correctly if the 
emulated code actually tries to do unaligned loads or stores. (This option 
is only meaningful when emulating MIPS CPUs, when the host architecture is 
Alpha or i386, and binary translation is enabled.)
.It Fl B
Disable dynamic binary translation. By default, bintrans
will be turned on if the host+target architecture combination is 
supported. Currently, the only supported target architecture for bintrans 
is MIPS, and the supported host architectures are Alpha and i386.
.It Fl C Ar x
Try to emulate a specific CPU type,
.Ar "x".
This overrides the default CPU type for the machine being emulated.
(Use
.Fl H
to get a list of available CPU types.)
.It Fl d Ar name
Add
.Ar name
as a disk image. By adding one or more modifier characters and then a
colon (":") as a prefix to
.Ar "name",
you can modify the way the disk image is treated. Available modifiers are:
.Bl -tag -width Ds
.It b
Specifies that this is a boot device.
.It c
CD-ROM.
.It d
DISK (this is the default).
.It f
FLOPPY.
.It gH;S;
Override the default geometry; use H heads and S sectors-per-track.
(The number of cylinders is calculated automatically.)
.It i
IDE.
.It r
Read-only (don't allow changes to be written to the file).
.It s
SCSI (this is the default for most machine types).
.It t
Tape.
.It 0-7
Force a specific ID number.
.El
.Pp
Unless otherwise specified, filenames ending with ".iso" or ".cdr" are 
assumed to be CDROM images. Most others are assumed to be disks. Depending
on which machine is being emulated, the default for disks can be either 
SCSI or IDE. Some disk images that are very small are assumed to be floppy 
disks. (If you are not happy with the way a disk image is detected, then 
you need to use explicit prefixes to force a specific type.)
.Pp
For floppies, the gH;S; prefix is ignored. Instead, the number of 
heads and cylinders are assumed to be 2 and 80, respectively, and the 
number of sectors per track is calculated automatically. (This works for 
720KB, 1.2MB, 1.44MB, and 2.88MB floppies.)
.It Fl I Ar x
Emulate clock interrupts at
.Ar x
Hz. (This affects emulated clock devices only, not actual runtime speed.
This disables automatic clock adjustments, which is otherwise turned on.)
(This option is probably only valid for DECstation emulation.)
.It Fl i
Display each instruction as it is being executed.
.It Fl J
Disable some speed tricks.
.It Fl j Ar n
Set the name of the kernel to
.Ar "n".
When booting from an ISO9660 filesystem, the emulator will try to boot 
using this file. (In some emulation modes, eg. DECstation, this name is passed 
along to the boot program. Useful names are "bsd" for OpenBSD/pmax, 
or "vmunix" for Ultrix.)
.It Fl M Ar m
Emulate
.Ar m
MBs of physical RAM. This overrides the default amount of RAM for the 
selected machine type.
.It Fl m Ar nr
Run at most
.Ar nr
instructions (on any cpu).
.It Fl N
Display nr of instructions/second average, at regular intervals.
.It Fl n Ar nr
Set nr of CPUs (for SMP experiments).
.It Fl O
Force a "netboot" (tftp instead of disk), even when a disk image is
present (for DECstation, SGI, and ARC emulation).
.It Fl o Ar arg
Set the boot argument (mostly useful for DEC, ARC, or SGI emulation).
Default
.Ar arg
for DEC is "-a", for ARC/SGI it is "-aN", and for CATS it is "-A".
.It Fl p Ar pc
Add a breakpoint. (Remember to use the "0x" prefix for hex.)
.It Fl Q
Disable the built-in PROM emulation. This is useful for running raw ROM
images from real machines.
.It Fl R
Use a random bootstrap cpu, instead of CPU nr 0. (For SMP experiments.)
.It Fl r
Dump register contents for every executed instruction.
.It Fl S
Initialize the emulated RAM to random data, instead of zeroes.
.It Fl T
Enter the single-step debugger on unimplemented memory accesses.
.It Fl t
Show a trace tree of all function calls being made.
.It Fl U
Enable slow_serial_interrupts_hack_for_linux.
.It Fl X
Use X11.
.It Fl x
Open up new xterms for emulated serial ports. (Default is to open up 
xterms when using configuration files, but not when starting an 
emulation with settings directly on the command line.)
.It Fl Y Ar n
Scale down framebuffer windows by
.Ar n
x
.Ar n
times.
.It Fl y Ar x
Set max_random_cycles_per_chunk to
.Ar x
(experimental).
.It Fl Z Ar n
Set the number of graphics cards, for emulating a dual-head or tripple-head
environment. (Only for DECstation emulation so far.)
.It Fl z Ar disp
Add
.Ar disp
as an X11 display to use for framebuffers.
.El
.Pp
Userland options:
.Bl -tag -width Ds
.It Fl u Ar emul-mode
Userland-only (syscall) emulation. (Use
.Fl H
to get a list of available emulation modes.) Some (but not all) of the
options listed under Other options above can also be used with userland
emulation.
.El
.Pp
General options:
.Bl -tag -width Ds
.It Fl D
Guarantee fully deterministic behavior. Normally, the emulator calls
srandom() with a seed based on the current time at startup. When the
.Fl D
option is used, the srandom() call is skipped, which should cause two 
subsequent invocations of the emulator to be identical, if all other 
settings are identical and no user input is taking place. (If this option 
is used, then
.Fl I
must also be used.)
.It Fl H
Display a list of available CPU types, machine types, and userland
emulation modes. (Most of these don't work. Please read the documentation
included in the
.Nm
distribution for details on which modes that actually work.)
.It Fl h
Display a list of all available command line options.
.It Fl K
Force the single-step debugger to be entered at the end of a simulation.
.It Fl q
Quiet mode; this suppresses startup messages.
.It Fl s
Show opcode usage statistics after the simulation.
.It Fl V
Start up in the single-step debugger, paused.
.It Fl v
Verbose debug messages.
.El
.Pp
Configuration file startup:
.Bl -tag -width Ds
.It @ Ar configfile
Start an emulation based on the contents of
.Ar "configfile".
.El
.Pp
For more information, please read the documentation in the doc/
subdirectory of the
.Nm
distribution.
.Sh EXAMPLES
The following command will start NetBSD/pmax on an emulated DECstation 
5000/200 (3MAX):
.Pp
.Dl "gxemul -e 3max -d nbsd_pmax.img"
.Pp
nbsd_pmax.img should be a raw disk image containing a bootable 
NetBSD/pmax filesystem.
.Pp
The following command will start an emulation session based on settings in 
the configuration file "mysession". The -v option tells gxemul to be
verbose.
.Pp
.Dl "gxemul -v @mysession"
.Pp
If you have compiled the small Hello World program mentioned in the
.Nm
documentation, the following command will start up an
emulated test machine in "paused" mode:
.Pp
.Dl "gxemul -E testmips -V hello_mips"
.Pp
(Paused mode means that you enter the interactive single-step debugger
directly at startup, instead of launching the Hello World program.)
.Pp
Please read the documentation for more details.
.Sh BUGS
There are many bugs. Some of the known bugs are listed in the BUGS
file in the
.Nm
source distribution, some are indirectly mentioned in the TODO file,
and some are mentioned in the source code itself.
.Pp
The binary translation subsystem is really terrible, but it is less
terrible than running without it.
.Pp
Userland (syscall-only) emulation doesn't really work yet.
.Pp
Emulation of MIPS CPUs is done differently from other emulation modes; the 
documentation sometimes only reflect the way things work with MIPS 
emulation, and it is incorrect when applied to e.g. ARM emulation.
.Pp
.Nm
does not simulate individual pipe-line stages or penalties caused by
branch-prediction misses or cache misses, so it cannot be used for
accurate simulation of any actual real-world processor.
.Pp
.Nm
is not timing-accurate.
.Sh AUTHOR
Anders Gavare <anders@gavare.se>
.Pp
See http://gavare.se/gxemul/ for more information.
1	.\" $Id: gxemul.1,v 1.34 2005/10/11 03:53:58 debug Exp $
2	.\"
3	.\" Copyright (C) 2004-2005 Anders Gavare. All rights reserved.
4	.\"
5	.\" Redistribution and use in source and binary forms, with or without
6	.\" modification, are permitted provided that the following conditions are met:
7	.\"
8	.\" 1. Redistributions of source code must retain the above copyright
9	.\" notice, this list of conditions and the following disclaimer.
10	.\" 2. Redistributions in binary form must reproduce the above copyright
11	.\" notice, this list of conditions and the following disclaimer in the
12	.\" documentation and/or other materials provided with the distribution.
13	.\" 3. The name of the author may not be used to endorse or promote products
14	.\" derived from this software without specific prior written permission.
15	.\"
16	.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26	.\" SUCH DAMAGE.
27	.\"
28	.\"
29	.\" This is a minimal man page for GXemul. Process this file with
30	.\" groff -man -Tascii gxemul.1 or nroff -man gxemul.1
31	.\"
32	.Dd OCTOBER 2005
33	.Dt GXEMUL 1
34	.Os
35	.Sh NAME
36	.Nm gxemul
37	.Nd an experimental machine emulator
38	.Sh SYNOPSIS
39	.Nm
40	.Op machine, other, and general options
41	.Op file Ar ...
42	.Nm
43	.Op general options
44	.Ar @configfile
45	.Nm
46	.Op userland, other, and general options
47	.Ar file Op Ar args ...
48	.Sh DESCRIPTION
49	.Nm
50	is an experimental instruction-level machine emulator. Several
51	emulation modes are available. In some modes, processors and surrounding
52	hardware components are emulated well enough to let unmodified operating
53	systems (e.g. NetBSD) run as if they were running on a real machine.
54	.Pp
55	The processor architecture best emulated by GXemul is MIPS, but other
56	architectures are also partially emulated.
57	.Pp
58	There are three ways to invoke the emulator:
59	.Pp
60	1. When emulating a complete machine, configuration options can be entered
61	directly on the command line.
62	.Pp
63	2. Options can be read from a configuration file.
64	.Pp
65	3. When emulating a userland environment (syscall-only emulation, not
66	emulating complete machines), then the program name and its argument
67	should be given on the command line. (This mode doesn't really work yet.)
68	.Pp
69	The easiest way to use the emulator is to supply settings directly on the
70	command line. The most important thing you need to supply is the
71	file argument. This is the name of a binary file (an ELF, a.out, COFF/ECOFF,
72	SREC, or a raw binary image) which you wish to run in the emulator. This file
73	might be an operating system kernel, or perhaps a ROM image file.
74	.Pp
75	If more than one filename is supplied, all files are loaded into memory,
76	and the entry point (if available) is taken from the last file.
77	.Pp
78	Apart from the name of a binary file, it is also necessary to select
79	which specific emulation mode to use. For example, a MIPS-based machine
80	from DEC (a DECstation) is very different from a MIPS-based machine
81	from SGI. Use
82	.Nm
83	.Fl H
84	to get a list of available emulation modes.
85	.Pp
86	There are two exceptions to the normal invocation usage mentioned above.
87	The first is for DECstation emulation: if you have a bootable
88	DECstation harddisk or CDROM image, then just supplying the diskimage via
89	the
90	.Fl d
91	option is sufficient. (The filename of the kernel can then be
92	skipped, as the emulator runs the bootblocks from the diskimage directly and
93	doesn't need the kernel as a separate file.)
94	The second is if you supply an ISO9660 CDROM disk image. You may then use
95	the
96	.Fl j
97	option to indicate which file on the CDROM filesystem that should be
98	loaded into emulated memory.
99	.Pp
100	Machine selection options:
101	.Bl -tag -width Ds
102	.It Fl E Ar t
103	Try to emulate machine type
104	.Ar "t".
105	This option is not always needed, if the
106	.Fl e
107	option uniquely selects a machine.
108	(Use
109	.Fl H
110	to get a list of types.)
111	.It Fl e Ar st
112	Try to emulate machine subtype
113	.Ar "st".
114	Use this together with
115	.Fl E .
116	(This option is not always needed, if a machine type has no subtypes.)
117	.El
118	.Pp
119	Other options:
120	.Bl -tag -width Ds
121	.It Fl A
122	Disable load/store alignment checks in some cases. This might give a small
123	increase in performance, but the emulator will not run correctly if the
124	emulated code actually tries to do unaligned loads or stores. (This option
125	is only meaningful when emulating MIPS CPUs, when the host architecture is
126	Alpha or i386, and binary translation is enabled.)
127	.It Fl B
128	Disable dynamic binary translation. By default, bintrans
129	will be turned on if the host+target architecture combination is
130	supported. Currently, the only supported target architecture for bintrans
131	is MIPS, and the supported host architectures are Alpha and i386.
132	.It Fl C Ar x
133	Try to emulate a specific CPU type,
134	.Ar "x".
135	This overrides the default CPU type for the machine being emulated.
136	(Use
137	.Fl H
138	to get a list of available CPU types.)
139	.It Fl d Ar name
140	Add
141	.Ar name
142	as a disk image. By adding one or more modifier characters and then a
143	colon (":") as a prefix to
144	.Ar "name",
145	you can modify the way the disk image is treated. Available modifiers are:
146	.Bl -tag -width Ds
147	.It b
148	Specifies that this is a boot device.
149	.It c
150	CD-ROM.
151	.It d
152	DISK (this is the default).
153	.It f
154	FLOPPY.
155	.It gH;S;
156	Override the default geometry; use H heads and S sectors-per-track.
157	(The number of cylinders is calculated automatically.)
158	.It i
159	IDE.
160	.It r
161	Read-only (don't allow changes to be written to the file).
162	.It s
163	SCSI (this is the default for most machine types).
164	.It t
165	Tape.
166	.It 0-7
167	Force a specific ID number.
168	.El
169	.Pp
170	Unless otherwise specified, filenames ending with ".iso" or ".cdr" are
171	assumed to be CDROM images. Most others are assumed to be disks. Depending
172	on which machine is being emulated, the default for disks can be either
173	SCSI or IDE. Some disk images that are very small are assumed to be floppy
174	disks. (If you are not happy with the way a disk image is detected, then
175	you need to use explicit prefixes to force a specific type.)
176	.Pp
177	For floppies, the gH;S; prefix is ignored. Instead, the number of
178	heads and cylinders are assumed to be 2 and 80, respectively, and the
179	number of sectors per track is calculated automatically. (This works for
180	720KB, 1.2MB, 1.44MB, and 2.88MB floppies.)
181	.It Fl I Ar x
182	Emulate clock interrupts at
183	.Ar x
184	Hz. (This affects emulated clock devices only, not actual runtime speed.
185	This disables automatic clock adjustments, which is otherwise turned on.)
186	(This option is probably only valid for DECstation emulation.)
187	.It Fl i
188	Display each instruction as it is being executed.
189	.It Fl J
190	Disable some speed tricks.
191	.It Fl j Ar n
192	Set the name of the kernel to
193	.Ar "n".
194	When booting from an ISO9660 filesystem, the emulator will try to boot
195	using this file. (In some emulation modes, eg. DECstation, this name is passed
196	along to the boot program. Useful names are "bsd" for OpenBSD/pmax,
197	or "vmunix" for Ultrix.)
198	.It Fl M Ar m
199	Emulate
200	.Ar m
201	MBs of physical RAM. This overrides the default amount of RAM for the
202	selected machine type.
203	.It Fl m Ar nr
204	Run at most
205	.Ar nr
206	instructions (on any cpu).
207	.It Fl N
208	Display nr of instructions/second average, at regular intervals.
209	.It Fl n Ar nr
210	Set nr of CPUs (for SMP experiments).
211	.It Fl O
212	Force a "netboot" (tftp instead of disk), even when a disk image is
213	present (for DECstation, SGI, and ARC emulation).
214	.It Fl o Ar arg
215	Set the boot argument (mostly useful for DEC, ARC, or SGI emulation).
216	Default
217	.Ar arg
218	for DEC is "-a", for ARC/SGI it is "-aN", and for CATS it is "-A".
219	.It Fl p Ar pc
220	Add a breakpoint. (Remember to use the "0x" prefix for hex.)
221	.It Fl Q
222	Disable the built-in PROM emulation. This is useful for running raw ROM
223	images from real machines.
224	.It Fl R
225	Use a random bootstrap cpu, instead of CPU nr 0. (For SMP experiments.)
226	.It Fl r
227	Dump register contents for every executed instruction.
228	.It Fl S
229	Initialize the emulated RAM to random data, instead of zeroes.
230	.It Fl T
231	Enter the single-step debugger on unimplemented memory accesses.
232	.It Fl t
233	Show a trace tree of all function calls being made.
234	.It Fl U
235	Enable slow_serial_interrupts_hack_for_linux.
236	.It Fl X
237	Use X11.
238	.It Fl x
239	Open up new xterms for emulated serial ports. (Default is to open up
240	xterms when using configuration files, but not when starting an
241	emulation with settings directly on the command line.)
242	.It Fl Y Ar n
243	Scale down framebuffer windows by
244	.Ar n
245	x
246	.Ar n
247	times.
248	.It Fl y Ar x
249	Set max_random_cycles_per_chunk to
250	.Ar x
251	(experimental).
252	.It Fl Z Ar n
253	Set the number of graphics cards, for emulating a dual-head or tripple-head
254	environment. (Only for DECstation emulation so far.)
255	.It Fl z Ar disp
256	Add
257	.Ar disp
258	as an X11 display to use for framebuffers.
259	.El
260	.Pp
261	Userland options:
262	.Bl -tag -width Ds
263	.It Fl u Ar emul-mode
264	Userland-only (syscall) emulation. (Use
265	.Fl H
266	to get a list of available emulation modes.) Some (but not all) of the
267	options listed under Other options above can also be used with userland
268	emulation.
269	.El
270	.Pp
271	General options:
272	.Bl -tag -width Ds
273	.It Fl D
274	Guarantee fully deterministic behavior. Normally, the emulator calls
275	srandom() with a seed based on the current time at startup. When the
276	.Fl D
277	option is used, the srandom() call is skipped, which should cause two
278	subsequent invocations of the emulator to be identical, if all other
279	settings are identical and no user input is taking place. (If this option
280	is used, then
281	.Fl I
282	must also be used.)
283	.It Fl H
284	Display a list of available CPU types, machine types, and userland
285	emulation modes. (Most of these don't work. Please read the documentation
286	included in the
287	.Nm
288	distribution for details on which modes that actually work.)
289	.It Fl h
290	Display a list of all available command line options.
291	.It Fl K
292	Force the single-step debugger to be entered at the end of a simulation.
293	.It Fl q
294	Quiet mode; this suppresses startup messages.
295	.It Fl s
296	Show opcode usage statistics after the simulation.
297	.It Fl V
298	Start up in the single-step debugger, paused.
299	.It Fl v
300	Verbose debug messages.
301	.El
302	.Pp
303	Configuration file startup:
304	.Bl -tag -width Ds
305	.It @ Ar configfile
306	Start an emulation based on the contents of
307	.Ar "configfile".
308	.El
309	.Pp
310	For more information, please read the documentation in the doc/
311	subdirectory of the
312	.Nm
313	distribution.
314	.Sh EXAMPLES
315	The following command will start NetBSD/pmax on an emulated DECstation
316	5000/200 (3MAX):
317	.Pp
318	.Dl "gxemul -e 3max -d nbsd_pmax.img"
319	.Pp
320	nbsd_pmax.img should be a raw disk image containing a bootable
321	NetBSD/pmax filesystem.
322	.Pp
323	The following command will start an emulation session based on settings in
324	the configuration file "mysession". The -v option tells gxemul to be
325	verbose.
326	.Pp
327	.Dl "gxemul -v @mysession"
328	.Pp
329	If you have compiled the small Hello World program mentioned in the
330	.Nm
331	documentation, the following command will start up an
332	emulated test machine in "paused" mode:
333	.Pp
334	.Dl "gxemul -E testmips -V hello_mips"
335	.Pp
336	(Paused mode means that you enter the interactive single-step debugger
337	directly at startup, instead of launching the Hello World program.)
338	.Pp
339	Please read the documentation for more details.
340	.Sh BUGS
341	There are many bugs. Some of the known bugs are listed in the BUGS
342	file in the
343	.Nm
344	source distribution, some are indirectly mentioned in the TODO file,
345	and some are mentioned in the source code itself.
346	.Pp
347	The binary translation subsystem is really terrible, but it is less
348	terrible than running without it.
349	.Pp
350	Userland (syscall-only) emulation doesn't really work yet.
351	.Pp
352	Emulation of MIPS CPUs is done differently from other emulation modes; the
353	documentation sometimes only reflect the way things work with MIPS
354	emulation, and it is incorrect when applied to e.g. ARM emulation.
355	.Pp
356	.Nm
357	does not simulate individual pipe-line stages or penalties caused by
358	branch-prediction misses or cache misses, so it cannot be used for
359	accurate simulation of any actual real-world processor.
360	.Pp
361	.Nm
362	is not timing-accurate.
363	.Sh AUTHOR
364	Anders Gavare <anders@gavare.se>
365	.Pp
366	See http://gavare.se/gxemul/ for more information.