readme.txt

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a minimum of 192 * 64K or 12MB of memory.  You can also edit the
worktodo.ini file directly.  For example:
	ECM=751,3000000,0,100,0,0,0,0
The first value is the exponent.  The second value is bound #1.  The
third value is bound #2 - leave it as zero.  The fourth value is the
number of curves to test.  The fifth value is no longer used. 
The sixth value is the specific curve to test - it is only used in
debugging.  The seventh value is 0 for 2^N-1 factoring, 1 for 2^N+1
factoring.  The eighth value is no longer used.

The P-1 choice lets you factor Mersenne numbers using the P-1 method of
factoring.  There is presently no web site which tells you how much
P-1 factoring has already been done on exponents.  You can also edit
the worktodo.ini file directly.  For example:
	Pminus1=751001,1000000,0,0,0
The first value is the exponent.  The second value is bound #1.  The
third value is bound #2.  The fourth value is 0 for 2^N-1 factoring,
1 for 2^N+1 factoring.  The fifth value is no longer used.

Round off checking.  This option will slow the program down by about 15%.
This option displays the smallest and largest "convolution error".  The
convolution error must be less than 0.49 or the results will be incorrect.
There really is no good reason to turn this option on.

The Priority menu is used to adjust the priority prime95 runs at.
You should not need to change this.  You might raise the priority
if you (or your coworker) just cannot live without a screen
saver (bad idea), or if you are running some ill-behaved program
that is using CPU cycles for no good reason.

The Manual Communication menu choice should only be used if the
automatic detection of an Internet connection is not working for you.
Using this option means you have to remember to communicate with the
server every week or two (by using this same menu choice).

The Unreserve Exponent choice lets you tell the server to unreserve
an exponent you have been assigned.  You might do this if a second computer
you had been running GIMPS on died or if you had been assigned an exponent
of one work type (such as a first-time-test) and now you have switched to
another work type (such as 10,000,000 digit numbers).  Any work you have
done on the unreserved exponent will be lost.

The Quit GIMPS menu choice is used when you no longer want this computer
to work on the GIMPS project.  You may rejoin at a later date.
If you are a PrimeNet user your unfinished work will be returned to the
server.  If you are a manual user, you need to send me email containing
your results.txt file and a note saying you are quitting.


OPTIONS MENU
------------

The CPU menu choice lets you tell the program what kind of CPU you
have and how much memory the program can use (see the earlier section
on "Setting available memory".  The program will normally figure out
the CPU type for you.  This information is used to give accurate time
estimates in the Test/Status menu choice.  It is also used, to choose
between integer based factoring (Cyrix and 486) and floating point based
factoring (Pentium and Pentium Pro).  There are also some optimizations
specific to the Pentium Pro and later CPUs in the Lucas-Lehmer primality test.
If you have an AMD K5 or Cyrix M2 chip, choose Cyrix 6x86.

The Preferences menu choice lets you control how often a line is
written to the main window and how often a line is written to
the results file.  It also lets you change how often
intermediate files (to guard against power failure and crashes)
are created.  You can control how often the program checks to
see if you are connected to the Internet.  The program polls
whenever it has new data to send to or work to get from the PrimeNet
server.  If you are low on disk space, you can select one intermediate 
file instead of two.  However, if you crash in the middle of writing
the one intermediate file, you may have to restart an exponent from
scratch.  You can also tell the program to be quiet, rather than 
beeping like crazy, if a new Mersenne prime is found.  You can also
make prime95 go idle whenever your laptop is running on battery power
(does not work under Windows NT/2000/XP).

The Torture Test choice will run a continuous self test.  This is great
for testing machines for hardware problems.  See the file stress.txt
for a more in-depth discussion of stress testing and hardware problems.

The Benchmark choice times the program on several FFT lengths.  You can
then compare your computer's speed to others list at
http://www.mersenne.org/bench.htm

The Tray Icon choice will cause prime95 to have a small icon on the taskbar
when it is minimized.  You can activate or hide the program by double-clicking
on the small icon.  If you place the cursor over the small icon, a tooltip will
display the current status.

The No Icon choice is only enabled if the Advanced Menu is activated
with the password.  Using this menu choice means there will be no
prime95 icon on the taskbar once you minimize the program - making it very
hard to reactivate!  You can reactivate the program by trying to execute
prime95 a second time.  Alternatively, you can turn this feature off by
editing prime.ini and change the line "HideIcon=1" to "HideIcon=0",
then reboot.

Checking the Start at Bootup menu choice will run prime95 as a service
that is started when your computer boots up.  Windows NT/2000/XP users need
administrator privileges to use this feature.  This method of starting prime95
is better than creating a shortcut to prime95 in the startup folder.  That
is because services run even when no one is logged on.  These are the details
you should be aware of:
	In Windows 95/98/Me:
The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices
registry entry is created.  You will not be able to tell any difference between
prime95 running as a service and prime95 running as an ordinary process.
	In Windows NT/2000/XP (without administrator privileges):
In this case the menu text is changed to "Start at Logon".  The
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run registry entry
is created.  Prime95 will run only when you are logged in.
	In Windows NT/2000/XP (with administrator privileges):
There are a few minor quirks when running as a service.  You shouldn't run
into these quirks in normal operation.  You can only change this option once
and it will take effect when the service is started or stopped.  You will
need to exit prime95 running as a normal process before starting the prime95
service.  The prime95 window will only appear on one users desktop.  Only
one prime95.exe program can be run as a service.  If you have a dual processor
system you'll want to run two instances of prime95.  Instead of running a
second prime95 from another directory, run the second prime95 from the same
directory with the -A1 switch (type "prime95 -A1" in a DOS window).
Finally, if you are worried about giving users access to a GUI service
running in the Local System account, you can turn off the "Allow service to
interact with desktop" option in the services control panel applet or run
the GUI-less NT service version available at
http://www.mersenne.org/freesoft.htm.  These options are more secure than
using the No Icon menu choice.


COMMAND LINE ARGUMENTS
----------------------

-An		This is used to run two or more copies of prime95
		from the same directory.  Using this command line argument
		causes prime95 to use a different set of filenames for the
		INI files, the results file, the log file, and the spool file.
		Just use a different value of n for each copy of
		prime95.exe you start.
-t		Run the torture test.  Same as Options/Torture Test.
-Wdirectory	This tells prime95 to find all its files in a different
		directory than the executable.


POSSIBLE HARDWARE FAILURE
-------------------------

If the message "Possible hardware failure, consult the readme file."
appears in the results.txt file, then prime95's error-checking has
detected a problem.  After waiting 5 minutes, the program will continue
testing from the last save file.

Could it be a software problem?  If the error is ILLEGAL SUMOUT and you are
running Windows 95/98/Me, then there is some chance that this is a software
problem.  A device driver or VxD may not be saving and restoring FPU state
correctly.  Windows NT/2000/XP protects prime95 from bad device drivers.
In that case ILLEGAL SUMOUT is very likely a true hardware error. The good news
is that prime95 recovers very well from ILLEGAL SUMOUT errors.  Try seeing
if the problem occurs only when a specific device is active or a specific
program is running.

The other two errors messages, SUMINP != SUMOUT and ROUND OFF > 0.40 are
caused by one of two things:
	1)  For reasons too complicated to go into here, the program's error
	checking is not	perfect.  Some errors can be missed and some correct
	results flagged as an error.  If you get the message "Disregard last
	error..." upon continuing from the last save file, then you may have
	found the rare case where a good result was flagged as an error.
	2)  A true hardware error.

If you do not get the "Disregard last error..." message or this happens
more than once, then your machine is a good candidate for a torture test.
See the stress.txt file for more information.

Running the program on a computer with hardware problems may produce
incorrect results.  This won't hurt the GIMPS project since all results
will be double-checked.  However, you could be wasting your CPU time.
If you are getting several errors during each primality test, then I
recommend using your machine to factor Mersenne numbers or run less
strenuous distributed computing projects at
http://www.mersenne.org/projects.htm.


LUCAS-LEHMER DETAILS
--------------------

This program uses the Lucas-Lehmer primality test to see if 2**p-1 is prime.
The Lucas sequence is defined as:
	L[1] = 4
	L[n+1] = (L[n]**2 - 2) mod (2**p - 1)
2**p-1 is prime if and only if L[p-1] = 0.

This program uses a discrete weighted transform (see Mathematics of
Computation, January 1994) to square numbers in the Lucas-Lehmer sequence.


DISCLAIMER
----------

THIS PROGRAM AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
PARTICULAR PURPOSE.


THANKS
------

Happy hunting and thanks for joining the search,
George Woltman
[e-mail]