0.3.6/man/gxemul.1

.\" $Id: gxemul.1,v 1.33 2005/10/07 22:45:34 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.
.It Fl B
Disable dynamic binary translation. By default, bintrans
will be turned on if the host+target architecture combination is 
supported.
.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 (for DEC, ARC, or SGI emulation).
Default
.Ar arg
for DEC is "-a", for ARC "-aN".
.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
.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 1.33 2005/10/07 22:45:34 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.
125	.It Fl B
126	Disable dynamic binary translation. By default, bintrans
127	will be turned on if the host+target architecture combination is
128	supported.
129	.It Fl C Ar x
130	Try to emulate a specific CPU type,
131	.Ar "x".
132	This overrides the default CPU type for the machine being emulated.
133	(Use
134	.Fl H
135	to get a list of available CPU types.)
136	.It Fl d Ar name
137	Add
138	.Ar name
139	as a disk image. By adding one or more modifier characters and then a
140	colon (":") as a prefix to
141	.Ar "name",
142	you can modify the way the disk image is treated. Available modifiers are:
143	.Bl -tag -width Ds
144	.It b
145	Specifies that this is a boot device.
146	.It c
147	CD-ROM.
148	.It d
149	DISK (this is the default).
150	.It f
151	FLOPPY.
152	.It gH;S;
153	Override the default geometry; use H heads and S sectors-per-track.
154	(The number of cylinders is calculated automatically.)
155	.It i
156	IDE.
157	.It r
158	Read-only (don't allow changes to be written to the file).
159	.It s
160	SCSI (this is the default for most machine types).
161	.It t
162	Tape.
163	.It 0-7
164	Force a specific ID number.
165	.El
166	.Pp
167	Unless otherwise specified, filenames ending with ".iso" or ".cdr" are
168	assumed to be CDROM images. Most others are assumed to be disks. Depending
169	on which machine is being emulated, the default for disks can be either
170	SCSI or IDE. Some disk images that are very small are assumed to be floppy
171	disks. (If you are not happy with the way a disk image is detected, then
172	you need to use explicit prefixes to force a specific type.)
173	.Pp
174	For floppies, the gH;S; prefix is ignored. Instead, the number of
175	heads and cylinders are assumed to be 2 and 80, respectively, and the
176	number of sectors per track is calculated automatically. (This works for
177	720KB, 1.2MB, 1.44MB, and 2.88MB floppies.)
178	.It Fl I Ar x
179	Emulate clock interrupts at
180	.Ar x
181	Hz. (This affects emulated clock devices only, not actual runtime speed.
182	This disables automatic clock adjustments, which is otherwise turned on.)
183	(This option is probably only valid for DECstation emulation.)
184	.It Fl i
185	Display each instruction as it is being executed.
186	.It Fl J
187	Disable some speed tricks.
188	.It Fl j Ar n
189	Set the name of the kernel to
190	.Ar "n".
191	When booting from an ISO9660 filesystem, the emulator will try to boot
192	using this file. (In some emulation modes, eg. DECstation, this name is passed
193	along to the boot program. Useful names are "bsd" for OpenBSD/pmax,
194	or "vmunix" for Ultrix.)
195	.It Fl M Ar m
196	Emulate
197	.Ar m
198	MBs of physical RAM. This overrides the default amount of RAM for the
199	selected machine type.
200	.It Fl m Ar nr
201	Run at most
202	.Ar nr
203	instructions (on any cpu).
204	.It Fl N
205	Display nr of instructions/second average, at regular intervals.
206	.It Fl n Ar nr
207	Set nr of CPUs (for SMP experiments).
208	.It Fl O
209	Force a "netboot" (tftp instead of disk), even when a disk image is
210	present (for DECstation, SGI, and ARC emulation).
211	.It Fl o Ar arg
212	Set the boot argument (for DEC, ARC, or SGI emulation).
213	Default
214	.Ar arg
215	for DEC is "-a", for ARC "-aN".
216	.It Fl p Ar pc
217	Add a breakpoint. (Remember to use the "0x" prefix for hex.)
218	.It Fl Q
219	Disable the built-in PROM emulation. This is useful for running raw ROM
220	images from real machines.
221	.It Fl R
222	Use a random bootstrap cpu, instead of CPU nr 0. (For SMP experiments.)
223	.It Fl r
224	Dump register contents for every executed instruction.
225	.It Fl S
226	Initialize the emulated RAM to random data, instead of zeroes.
227	.It Fl T
228	Enter the single-step debugger on unimplemented memory accesses.
229	.It Fl t
230	Show a trace tree of all function calls being made.
231	.It Fl U
232	Enable slow_serial_interrupts_hack_for_linux.
233	.It Fl X
234	Use X11.
235	.It Fl x
236	Open up new xterms for emulated serial ports. (Default is to open up
237	xterms when using configuration files, but not when starting an
238	emulation with settings directly on the command line.)
239	.It Fl Y Ar n
240	Scale down framebuffer windows by
241	.Ar n
242	x
243	.Ar n
244	times.
245	.It Fl y Ar x
246	Set max_random_cycles_per_chunk to
247	.Ar x
248	(experimental).
249	.It Fl Z Ar n
250	Set the number of graphics cards, for emulating a dual-head or tripple-head
251	environment. (Only for DECstation emulation so far.)
252	.It Fl z Ar disp
253	Add
254	.Ar disp
255	as an X11 display to use for framebuffers.
256	.El
257	.Pp
258	Userland options:
259	.Bl -tag -width Ds
260	.It Fl u Ar emul-mode
261	Userland-only (syscall) emulation. (Use
262	.Fl H
263	to get a list of available emulation modes.) Some (but not all) of the
264	options listed under Other options above can also be used with userland
265	emulation.
266	.El
267	.Pp
268	General options:
269	.Bl -tag -width Ds
270	.It Fl D
271	Guarantee fully deterministic behavior. Normally, the emulator calls
272	srandom() with a seed based on the current time at startup. When the
273	.Fl D
274	option is used, the srandom() call is skipped, which should cause two
275	subsequent invocations of the emulator to be identical, if all other
276	settings are identical and no user input is taking place. (If this option
277	is used, then
278	.Fl I
279	must also be used.)
280	.It Fl H
281	Display a list of available CPU types, machine types, and userland
282	emulation modes. (Most of these don't work. Please read the documentation
283	included in the
284	.Nm
285	distribution for details on which modes that actually work.)
286	.It Fl h
287	Display a list of all available command line options.
288	.It Fl K
289	Force the single-step debugger to be entered at the end of a simulation.
290	.It Fl q
291	Quiet mode; this suppresses startup messages.
292	.It Fl s
293	Show opcode usage statistics after the simulation.
294	.It Fl V
295	Start up in the single-step debugger, paused.
296	.It Fl v
297	Verbose debug messages.
298	.El
299	.Pp
300	Configuration file startup:
301	.Bl -tag -width Ds
302	.It @ Ar configfile
303	Start an emulation based on the contents of
304	.Ar "configfile".
305	.El
306	.Pp
307	For more information, please read the documentation in the doc/
308	subdirectory of the
309	.Nm
310	distribution.
311	.Sh EXAMPLES
312	The following command will start NetBSD/pmax on an emulated DECstation
313	5000/200 (3MAX):
314	.Pp
315	.Dl "gxemul -e 3max -d nbsd_pmax.img"
316	.Pp
317	nbsd_pmax.img should be a raw disk image containing a bootable
318	NetBSD/pmax filesystem.
319	.Pp
320	The following command will start an emulation session based on settings in
321	the configuration file "mysession". The -v option tells gxemul to be
322	verbose.
323	.Pp
324	.Dl "gxemul -v @mysession"
325	.Pp
326	If you have compiled the small Hello World program mentioned in the
327	.Nm
328	documentation, the following command will start up an
329	emulated test machine in "paused" mode:
330	.Pp
331	.Dl "gxemul -E testmips -V hello_mips"
332	.Pp
333	(Paused mode means that you enter the interactive single-step debugger
334	directly at startup, instead of launching the Hello World program.)
335	.Pp
336	Please read the documentation for more details.
337	.Sh BUGS
338	There are many bugs. Some of the known bugs are listed in the BUGS
339	file in the
340	.Nm
341	source distribution, some are indirectly mentioned in the TODO file,
342	and some are mentioned in the source code itself.
343	.Pp
344	The binary translation subsystem is really terrible, but it is less
345	terrible than running without it.
346	.Pp
347	Userland (syscall-only) emulation doesn't really work yet.
348	.Pp
349	.Nm
350	does not simulate individual pipe-line stages or penalties caused by
351	branch-prediction misses or cache misses, so it cannot be used for
352	accurate simulation of any actual real-world processor.
353	.Pp
354	.Nm
355	is not timing-accurate.
356	.Sh AUTHOR
357	Anders Gavare <anders@gavare.se>
358	.Pp
359	See http://gavare.se/gxemul/ for more information.