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@@ -0,0 +1,310 @@ +- What is memtest86+, what do I use it for? + + Memtest86+ is a utility designed to test whether your memory is in working + order. It repeatedly writes an enormous amount of different patterns to all + memory locations and reads them back again and verifies whether the result + of the read is the same as what was written to memory. + + There can be a multitude of reasons for running memtest, but foremost of all + is of course to test whether your memory modules might be bad. Whenever you + suspect your modules to be bad because of system crashes, lockups or reboots + it would be nice to know whether the modules are in working order. + Memtest86+ is a utility which tries to answer that question for you. + + Another common use exists in the overclocking scene. When overclocking a + system you are essentially pushing your system to the limits and at some + point it will simply give way and break. Unfortunately there isn't a clear + cut way of deciding whether a system is still working correctly. Because of + the complexity of a computer a system which is pushed to the limits doesn't + just break completely when it starts to fail, instead little errors start + showing up in many different places in the system growing more frequent and + widespread the more the system is pushed. Each one of these little errors + can lead to a crash of your system but can also go unnoticed for days or + weeks in a running system. The art so to speak of overclocking is thus to + push the system as far as it can go without introducing any such errors. As + memory is usually one of the first places these such errors start coming up + a memory test is very useful. + +- How do I get it to run? + + There are several ways to use memtest, which are described below: + + + Run from floppydisk + + Memtest86+ is directly executable by any modern x86 compatible machine, by + writing the bootable binary to a floppy disk one can boot from the disk to + run memtest. + + Simply download the appropriate package, the Pre-Compiled Bootable Binary + (.gz) package for Linux users and the Pre-Compiled package for Floppy (DOS + - Win) for Windows users. + + For Windows, unzip the package into a directory like C:\memtest, insert a + blank floppy into your a: disk drive and run the install.bat file. As the + install prompts you, to use memtest directly, leave the disk in the drive + and reboot your machine. + + For Linux, unpack the package into your home directory, insert a blank + floppy into your floppy drive and execute 'dd if=~/memtest+-1.xx.bin.gz + of=/dev/fd0 conv=osync' replacing 1.xx with the correct version number of + the memtest86+ you downloaded. To run memtest immediately reboot your + machine. + + Your machine should now boot from the disk, display the word Loading + folowed by a series of periods and then show a screen much like the + screenshots on the memtest86+ web page. The test is automatically started. + + If your machine simply boots back into Windows/Linux you will most likely + have to configure your BIOS to attempt to boot from floppy disk on + startup, refer to your computer's/mainboard's manual how to do this. + + When you are done testing simply remove the floppy and reset your + computer, if ever you want to execure the test again simply reinsert the + disk and reboot/start your computer. + + + Run from CD + + Memtest86+ is directly executable by any modern x86 compatible machine, by + writing the iso to a CD one can boot from the CD to run memtest. + + Simply download the appropriate package, the Download - Pre-Compiled + Bootable ISO (.gz) for Linux users and the Pre-Compiled Bootable ISO + (.zip) for Windows users. + + For Windows, unzip the package into a directory like C:\memtest. You will + now see a file called memtest86+-1.xx.iso in this directory. You will need + to burn this file to a CD with a CD recording program. Do note however + that you should not make a regular data CD on which you for instance write + your text documents and holiday photographs. Instead the iso file is a so + called image of a CD, it is a direct copy of a CD. Your CD recording + program will most likely have a feature called burn image or something to + that effect which you should use to burn the CD. + + For linux, unzip the package into your home directory. and execute + 'cdrecord dev=<your burner> ~/memtest86+-1.xx.iso' where you replace <your + burner> with the scsi address of your CD burner and replace 1.xx with the + correct version number of the memtest86+ your downloaded. + + When the burning completed your drive will most likely have ejected the CD + and you should have a bootable memtest86+ CD. To run the test directly + reinsert the CD and reboot your machine. + + Your machine should now boot from the CD, display the word Loading folowed + by a series of periods and then show a screen much like the screenshots on + the memtest86+ web page. The test is automatically started. + + If your machine simply boots back into Windows/Linux you will most likely + have to configure your BIOS to attempt to boot from CD-ROM drive on + startup, refer to your computer's/mainboard's manual how to do this. + + When you are done testing simply remove the CD and reset your computer, if + ever you want to execure the test again simply reinsert the CD and + reboot/start your computer. + + + Run from USB Flash drive + + FIXME + + + Run from boot manager + + FIXME + +- How long does memtest86+ run? How do I stop it? + + Memtest86+ runs indefinately unless you stop it. It does however repeat the + same tests over and over again. Memtest86+ contains a number of different + tests which each take different approaches in trying to expose any errors in + your memory. In the top right of your screen you can see the progress of + each test in the lower of the two progress bars. The topmost progress bar + shows the progress of a pass, each pass consists of all the tests in the + memtest suite. + + Thus all tests are executed in one pass, so does that mean that no errors + will show after the first pass if that pass didn't reveal any errors? Well + no, there are several reasons why errors might only show up after a number + of passes. Firstly as of this writing, the latest version of memtest also + includes a test which uses random test patterns, each pass these patterns + will of course be different. Secondly some types of errors simply don't show + up until the system has been running for a while or are very critical on a + certain timing condition, or other such conditions. + + To conclude, one successful pass of memtest will give you a pretty good idea + that your memory is ok, only in rare cases will there be errors showing + after the first pass. To be sure though simply have the test run overnight + or even for a couple of days depending on the level of importance of the + system. + +- How many errors are acceptable? + + No errors are acceptable. Even if there is just one error, something is + amiss which can cause your system to crash. Of course what the cause of the + errors is you will still have to determine. + +- What do I do when I get errors? + + Firstly, don't start drawing any conclusions. You only know that memtest86+ + is giving your errors, not what the cause is. Unfortunately it is not a + straightforward exercise to decisively test the memory in an actual system. + This is because a computer is not just built up of some memory, but also + includes many other elements such as a memory controller, cache, a cache + controller, algorithmic and logic units, etc, all of which contribute to the + machine. If there are faults in any of these other parts of the computer you + will likely also see errors showing up in memtest. + + So what to do? First verify that the BIOS settings of your machine are + correctly configured. Look up the memory timing settings applicable to the + brand and type of memory modules you have and check they match your BIOS + settings, correct them if they don't and run memtest again + + Ok, you have all the settings correctly set and you're still getting errors. + Well of course a very likely cause are the memory modules and the logical + course of action is to look into them further. + + If you are well stocked, have a few other machines at your disposal, or just + want to spend the cash for some new modules the best way to test if the + cause are your memory modules is just to replace them and test again. If you + are less fortunate though there is still something you can do. + + If you have more then one module in your system, test them one by one, if + one is consistently giving errors and another is consistently showing no + errors it's a pretty good bet that the module giving the errors is simply + defective. To exclude the possibility that a defective slot is throwing your + results, use the same slot to test each different module. + + If each module by itself shows no errors, but when you place two or more + modules into the machine at the same time you do get errors, you are most + likely stuck with a compatibility issue and unfortunately there isn't a + whole lot you can do about it. Be sure to check your computer/motherboard + manual to see if the setup you are trying is allowed, some boards require + special restrictions in the sizes of modules, the order of modules, the + placement of double sided and single sides modules and more of such things. + + If you have only one module in your system, or all modules are giving + errors, there are only very few options left. The only thing you can do + really is to try the module(s) in another slot. Finally simply try out + different orders of the memory modules, although your manual might not + mention anything on the matter sometimes there simply exist timing or other + issues which can be resolved by changing the order of your modules. And of + course test each slot by putting a single module into that slot and running + memtest on it. + + In the end if you still have not been able to localize the problem you will + have to find a replacement module to establish whether the problem lies in + your modules. See if you can borrow a module from someone else. + + When you have replaced the memory by new memory and the errors still + persist, first check if you can rule out any compatibility issues or timing + issues. If you are sure the memory should work in the system the cause of + the errors must obviously lie someplace else in the system. + + The only way to find out where, is by trial and error really. Simply start + replacing and/or removing parts of your computer one by one, running memtest + each time you changed anything, until the errors are resolved. + +- I'm getting errors in test #x, what doest that mean? + + Interpreting memtest results is as scientific an endeavour as testing + whether a person is a witch by the methods used in Monty Python's Holy + Grail. In short, don't even start, it's not going to get you anywhere. Just + interpret any error as you should any other and use the methods descibed in + the previous question to determine the cause. + +- I'm getting errors in test #5 and/or #8 and have read a lot about it. + + Yes there are just about enough discussions on the topic to fill a book, but + it all boils down to the answer given above. The only thing that can be said + is that many a times, when memory latencies are incorrectly set in the BIOS + you will experience errors in test #5 and #8. (Though #8 does not exist + anymore as of version 1.40 and might be reinstated as a different test in a + later version.) This does however NOT mean that errors in these tests are + always the cause of incorrect settings, your memory might just as well be + defective. + +- I'm getting errors in memtest on one machine, but not when I put the same + memory in another, what does that mean? + + It can mean one of two things: + - The machine that is giving the errors is defective. Errors don't just + orginate from the memory module itself, but can also be caused by + defects in the cpu, chipset, motherboard, PSU and even by timing issues + introduced by any other component in the machine. + - The machine giving the errors is imposing stricter timing than the other + which the memory module simply can't cope with. If the module should + work with the machine according to its specifications then it most + likely is defective. + +- Which memory is tested? + + As much as possible of the system memory is tested. Unfortunately memtest86+ + can usually not test all of the memory. The reason for this is that todays + processors have become so complex that they require a small amount of memory + to keep accounting data of the processor state. If memtest were to write + over these areas the state of the processor becomes invalid and it's + behaviour unpredictable. Alas it is also impossible to relocate these areas + in the memory. + + This means that a small area of your memory can not be tested by memtest. If + this part of the memory is defective you will know soon enough though as the + processor, or parts of the processor simply won't work correctly if this + part of your memory is defective. Do realise though that in very rare cases + memtest will show no errors even though the module is defective, not because + memtest can't detect the error, but because memtest can't test the area the + error is located in. + +- When I select BIOS-ALL I get many errors / my machine crashes. + + This is normal. With todays computers this option should never be selected. + See the previous question about the reason for the errors. + +- I want to use memtest on a multiboot CD, how do I do this? + + This is of course very dependent on which boot loader you use for your CD. + Below is a description of how to set up a multiboot CD including memtest+ + with isolinux, if you have experience with any other bootloader(s) please + consider writing a small description of using memtest with that bootloader + for the FAQ. + + -isolinux + + For general instructions on how to make a bootable CD with isolinux see + the syslinux website and the manual. What you need to do to get memtest + working is as follows. + + Download the Pre-Compiled Bootable Binary, the .gz if you are working + under linux, the .zip if you are working under windows. Unpack the file + from the package and rename it to an 8.3 filename with an extension other + than .bin, renaming to memtest. (without an extension) is a good choice. + + Put the file somewhere in your CD directory structure, for example in + images/memtest and edit your config file to include the following: + + label memtest + kernel /images/memtest + + If you want to boot memtest automatically insert or change a line at the + top to: + + default memtest + + If you want to display a prompt from which you can start memtest add or + change the lines at the top to: (Change the timeout to suit your needs) + + prompt 1 + timeout 200 + +- If memtest86+ shows no errors does that mean my memory is not defective? + + Of course no answers are definitive, no matter how good memtest86+ will + eventually become there is always the possibility that a particular type of + error will go unnoticed. As long as you are having no problems with the + system it will be pretty safe to say that the modules are good. If you are + having problems with the system however you will just have to check by trial + and error, ie swapping the modules for new ones and/or testing with modules + of a different brand/type. + +- When I run install.bat it doesn't write anything to floppy. + + You most likely have unpacked the memtest+-1.xx.floppy.zip file into a + folder with a long pathname and/or containing + and - signs. It seems + rawrite doesn't like that. Just move the files you unpacked to a directory + like c:\memtest and execure it from there. |