How Do You Know if Prime95 Fails
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Terminal updated: June one, 2008
Torture test your CPU with Prime95
Installation And Running Tests
Prime95 is a programme which searches for very large prime numbers. It has also gained a reputation for getting errors on computers which are even slightly unstable. If at that place is any trouble with your CPU, your RAM, or the parts of your motherboard which are the interface between your CPU and RAM, then Prime95 has a tendency to neglect. This is a very useful characteristic if your computer is flakey and y'all're not sure which component is causing the problem. If your computer can run Prime95 for 24 hours without whatever errors, then you can usually assume that your CPU and the parts of the motherboard which interface with the CPU and RAM, are stable and working well. The programme is costless and you can download information technology from here.
Prime95 is a distributed program which spreads the work amongst large numbers of computers. When y'all run it for the first time, click the "Just Stress Testing" button when asked. But if you would like to contribute some spare CPU cycles to assistance find prime numbers, past all means printing the "Join GIMPS" button.
To test your computer, run Prime95 and click the "Options" menu and then select "Torture Test".
And so select a test and click "OK". In this example it's "In-identify large FFTs" which is the best test to run for single core CPUs. Run the test for a few hours. If you lot want to exist thorough then allow it run for 24 hours. To stop the test, click the "Examination" menu and so click "Terminate".
The example higher up shows a successful run. Prime95 checks its calculations against known results and so if something goes wrong it will stop automatically. It'due south besides been known on occasion to crash unstable machines.
If it crashes or finishes with an fault as shown above, and so you lot've got a hardware problem to deal with.
Kinds Of Torture Tests
The torture test window presents yous with three fix-made tests and an option to create a custom test. And so the obvious question is: which test should you run? The answer depends on what y'all're trying to do. First let's look at the kinds of tests which are available.
In instance you're interested, "FFT" stands for fast fourier transform. It's used in Prime95 to quickly calculate the square of very big numbers.
The "Custom" exam allows you to create your own test. The "Min FFT size (in K)" and "Max FFT size (in K)" permit you to choice the minimum and maximum size of the FFTs washed in the exam. The sizes you select are not the corporeality of memory used by the tests. The size value times 1024 is actually the number of points used in the FFT. Prime95 is non actually capable of doing FFTs of any capricious size. It can do only sizes in the following list: 8, x, 12, 14, sixteen, twenty, 24, 28, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 448, 512, 640, 768, 896, 1024, 1280, 1536, 1792, 2048, 2560, 3072, 3584, and 4096. When testing, Prime95 cycles through the sizes in the list which fall within the min to max range which you've entered. Prime95 (version 23.viii.1 and maybe others) has a problems which causes the program to hang if y'all enter a range which doesn't include any sizes from the list. Make sure that a custom range always includes at to the lowest degree one size from the list.
The "Time to run each FFT size (in minutes)" value controls how much time Prime95 spends running FFT tests of a given size. Once it has tested 1 size for that long, it moves on to the next size. It cycles continuously through the sizes within the min to max range until it gets an error or you terminate the test.
If the "Run FFTs in-place" box is checked, then the results of the FFTs are stored over the FFT points. That basically means that information technology uses the same RAM area over and over and only uses plenty to do the calculations. If the box is unchecked then Prime95 cycles through RAM every bit information technology runs through the tests and the total amount of RAM used is the value in "Retentivity to use (in MB)".
The "Small FFTs" test uses relatively pocket-sized FFTs which can fit into the CPU enshroud. As a consequence, the minor FFT test is the one which accesses your main memory the least simply it still makes some retentiveness accesses. Prime95 automatically creates a FFT size range which will fit into the L2 enshroud of your CPU.
The "In-identify large FFTs" examination uses relatively large FFTs which cannot fit into the CPU enshroud so this exam accesses principal memory a lot. It merely accesses a relatively small amount of primary memory because it runs the FFTs in-place so it accesses the aforementioned RAM over and over.
The "Blend" test uses FFTs with sizes which range from very small to very large. The FFTs are non run in-place so the tests wheel through RAM. The blend test automatically picks a "Memory to utilise" value which uses up all the RAM in the computer. This is the version of the examination which is most probable to fail if you take bad RAM. Note that on some computers running some versions of Prime95, the alloy examination allocates more than retentiveness than can fit into the physical RAM in the computer. When that happens, Windows has to employ virtual memory and the test ends upwardly accessing the difficult disk a lot. That ruins the test because the CPU isn't doing anything while information technology is waiting for the difficult disk to access the data whereas the test is actually supposed to be keeping the CPU busy at all times in order to stress it. Yous can tell that the exam isn't working properly if the hd action light is on almost of the time. When the blend test is running properly, the hard disk drive is simply accessed occasionally. If you're running Windows 2000 or Windows XP then you lot tin can also check whether the CPU is fully utilized in the task managing director. If the alloy exam has allocated also much retentivity then end the test and bring up the "Run a Torture Test" window and make sure "Blend" is selected. So select "Custom", reduce the value in "Retentiveness to use (in MB)" to a somewhat smaller value, and then run the exam again. Go along until you find a pocket-sized enough value which works properly.
Which Torture Test Should You lot Run?
Prime95 can stress exam three parts of your computer: the CPU, the motherboard RAM, and the CPU/RAM interface. On an Athlon 64, the motherboard RAM is connected directly to the CPU. So with an Athlon 64, the CPU/RAM interface is a memory controller built into the CPU. On most other CPUs, the RAM is continued to a northbridge chip on the motherboard which is connected to the CPU through the front side bus. And so on those CPUs, the CPU/RAM interface is the front side bus. All kinds of Prime95 torture tests stress the CPU. Both the in-place large FFTs examination and the blend test also test the CPU/RAM interface while the CPU is under stress. You shouldn't use Prime95 as a RAM exam. Information technology's simply non as thorough as something similar MemTest86. Real retentivity testers run carefully selected exam patterns to maximize the chances of finding a trouble and Prime95 doesn't do that. Prime95 is primarly used to find unstable CPUs and to test your CPU/RAM interface while the CPU is nether stress.
The more work your CPU is doing, the hotter information technology gets. Equally a silicon fleck gets hotter, it slows down. Every bit a outcome, its maximum stable clock charge per unit decreases as it gets hotter. That'due south why overclockers spend and then much fourth dimension trying to improve their cooling systems. Cooler is faster. Hotter is slower. A stable reckoner is one with components which are stable when the machine is under maximum stress. And so your goal should be to use the most stressful tests in Prime95.
| Test | CPU Temperature |
|---|---|
| idle (no test running) | 34.3C |
| MemTest86 | 47.3C |
| Prime95: small FFTs | 48.8C |
| Prime95: in-place large FFTs | 49.5C |
| Prime95: blend | 49.3C |
The tests above were run on a 3.2GHz Pentium 4. I don't accept temperature tests on other CPUs but from what I've seen in posts on the internet, they besides accept the same relative relationships. The in-identify big FFTs test is the hottest of the three ready-fabricated tests merely similar it says in Prime95's "Run a Torture Examination" window. And since it runs large FFTs, it'southward also doing a lot of memory accesses so it tests your CPU/RAM interface. It runs hotter than the small FFTs exam because that test isn't accessing RAM very much so it'due south not heating up the CPU/RAM interface and that part of the CPU consumes quite a bit of power. The blend test tends to run a bit cooler than the in-place big FFTs exam probably because the blend test is sitting and waiting for the memory accesses longer than the in-place large FFT test. So if you just want to run a single examination, and then run the in-identify large FFT. It heats your CPU the most and information technology also tests your CPU/RAM interface when the CPU is at its hottest. It'southward not a thorough RAM test merely then neither is the alloy examination and blend doesn't stress the CPU as much as in-place large FFT.
Too note that MemTest86 is not every bit good a exam of your CPU/RAM interface as Prime95 because it doesn't heat the CPU as much. MemTest86 is still heating up the CPU quite a bit, just Prime95 gets it hotter because information technology's using the floating point units in the CPU very heavily. MemTest86 is meliorate than Prime95 at finding bad RAM just it isn't as proficient as Prime95 at stressing the CPU/RAM interface. If you want to be thorough in testing the CPU, the RAM, and the CPU/RAM interface and then you should really run both Prime95 and MemTest86.
| Prime95 Instance #i | Prime95 Instance #ii | Temperature |
|---|---|---|
| no examination running | no examination running | 34.4C |
| Small FFTs | no test running | 48.7C |
| In-place large FFTs | no exam running | 49.5C |
| Alloy | no test running | 49.4C |
| Small FFTs | Small FFTs | 50.6C |
| Small FFTs | In-place big FFTs | 50.6C |
| Modest FFTs | Blend | l.6C |
| In-place large FFTs | In-place big FFTs | fifty.4C |
| In-place large FFTs | Alloy | 50.5C |
| Blend | Alloy | 49.8C |
These tests were run a iii.2GHz Pentium 4 with hyperthreading enabled on Windows XP. It ran about ane degree centrigrade hotter running ii copies of Prime95 than when running simply 1 copy. Using hyperthreading increases ability consumption in the CPU. It also runs hotter considering when i thread is waiting for the RAM to reply, the other thread wakes upward and continues to exercise calculations within the CPU. Hyperthreading is very good at keeping everything in the CPU busy. All the dual case tests seem to run at virtually the aforementioned temperature (at least within the limits of my low-budget thermocouple to measure) except for the tests where both are doing lots of memory accesses. And then if you are running with hyperthreading enabled, the best overall choice is to run one example of the small FFTs examination and another example of the in-place large FFTs test but you could likewise run a small FFTs along with a blend if have an urge to cycle through all of your RAM.
If you take a multi-CPU car then you should run one instance of Prime95 for each CPU. If the cores share 1 memory controller then you'll probably get maximum stress past running the blend test on i CPU and running a small FFTs test on each of the other cores.
If you run Prime95 and so effort to beginning another copy of Prime95, yous only cease up with one instance of the programme running. In society to run two Prime95 tests at the same time, yous need to invoke the program using the "A" command line switch. Make a shortcut to Prime95 and put it on your desktop. So brand a second shortcut to Prime95. You can create a 2nd shortcut by doing a correct-click drag and driblet of the offset shortcut onto the desktop and selecting "Create Shortcut Here". And then right-click the second shortcut, select "Properties", then select the "Shortcut" tab. Then get to the "Target:" field and add together "-A1" to the end. If you want to be able to run more than instances then create another shortcut copy with "-A2" so on. Each shortcut volition open upwardly a separate example of Prime95 so you can run more than one examination at a time.
You lot can cheque that all of your CPUs are fully loaded in the Windows Task Manager. The Performance tab has a handy CPU Usage History display for each CPU. They are displayed even if you're using hyperthreading rather than full CPU cores. Your goal is to get all of your CPUs running at 100%. If any are less than 100% then you lot're non doing the torture test at total strength. Running any other programs at the same time volition reduce your processor load. It will reduce it even further if a program accesses a disk drive. It's best to run only Prime95 and no other programs if you want to maximize the load on your CPU.
When you run ii or more instances of Prime95 on a multi-CPU motorcar, each instance doesn't really settle down and run only on one CPU. The instances jump around a piffling between CPUs. You tin can see that behaviour if yous start upwardly merely one instance of Prime95. The CPU Usage History window in the Job Director will prove the program running on both CPUs. You don't end upwards with one CPU at 100% and the other CPUs at 0%. Prime95 contains a facility to force an instance of the programme to run on only one CPU. Go to the main Prime95 window and click the Advanced menu and then select Affinity. So you'll get the dialog window shown in a higher place. Y'all can assign that instance of Prime95 to a detail CPU past unchecking the "Allow program run on whatever CPU" box. So enter the CPU number into the "Specific CPU to run on:" box. The CPU numbers start at 0 and count upwards. Merely assign each instance of Prime95 to a split CPU number and they'll stop jumping between CPUs. If Prime95 is already running and then you accept to terminate it and then start it over again before it will restrict itself to the CPU y'all've assigned. Co-ordinate to Prime95, you'll get ameliorate functioning by assigning process affinities. That means that the CPUs should run a trivial hotter which is ameliorate for testing. I've tried an Athlon 64 X2 and a Pentium 4 with hyperthreading both with affinities and without them and I couldn't measure whatever temperature difference on either CPU. It may be that the Windows task switching overhead was a college percentage of CPU time on older, slower CPUs and so it used to make more of a difference. With both of my CPUs it didn't matter whether I used processor affinities or not. But if you feel the urge to get your CPUs running at exactly 100% then you can expend the few seconds it takes to set up the processor affinities.
What Do Yous Practice If The Test Fails?
If your car passes Prime95, yous tin can feel fairly confident that your car is stable. But if it fails Prime95, it doesn't point direct to the component which is responsible. Information technology's simply not that easy to completely isolate the problem which causes Prime95 to neglect. Information technology's unremarkably the CPU but sometimes information technology's something else. The only way to be 100% certain is to swap in replacement components until the trouble is fixed. You just have to do every bit many tests as you can to make your best judge about which component is responsible earlier deciding which one to replace or adjust.
The vast majority of computers which fail the Prime95 test get the "FATAL Fault: Rounding" case shown upwardly to a higher place. Usually information technology happens apace but it can take hours on some computers. But people'due south machines have besides been known to occasionally crash or hang. When Prime95 fails in any way, the very first matter you should do is run a retention test to dominion that possibility out. MemTest86 is a very thorough retentivity testing programme (installation instructions here). If your retentivity passes the tests then you're pretty much downwards to the CPU and the CPU/RAM interface as the almost likely causes although there are another possibilities.
If you're running a CPU like the Athlon 64 which has its CPU/RAM interface integrated into the CPU, then if your RAM has passed tests yous tin pretty much blame your CPU. If you have the other kind of CPU which accesses its RAM by communicating with a northbridge flake on the motherboard, then your CPU is probably the problem but the northbridge could besides be responsible. The RAM data is passed in both directions between the CPU and northbridge and if the northbridge is a picayune weak, information technology may have bug communicating with a hot CPU. If you lot're not sure what to arraign then you can attempt running merely the "small FFTs" test. Information technology does very few RAM accesses while running the test. If it fails, so information technology's very likely to exist the CPU which is at fault. Unfortunately, that's non 100% guaranteed because even the pocket-size FFTs exam still accesses RAM and does other things like read and write disk files.
CPU overheating is a common cause of Prime95 failures. Prime95 pushes your CPU harder than almost all programs then it'southward entirely possible that information technology'south much hotter when running Prime95 than any other plan you run including games. It'southward worth opening up your machine and making sure that your CPU heatsink and fan are working properly. I've seen drops of 5 degrees centigrate in Prime95 just by cleaning the dust out of a CPU heatsink. Modern CPUs utilize lots of power and they can get very hot if anything is wrong with their cooling organization. Most computers come with monitoring programs which can display the current voltages and various temperatures in your computer. If yous don't have one then you may exist able to find a program on the internet which is uniform with your motherboard. A costless program which works with most hardware is SpeedFan. Motherboard Monitor is compatible with many older motherboards made in 2005 or before. You can apply a monitoring program to check that your CPU temperature is reasonable. The temperatures reported by those programs are not all that accurate but it'southward still worth the trouble of comparing with other peoples' temperatures. You can find them by doing an internet search on the name of your CPU and "elevation idle temperatures".
If you've built your own computer and know your style around your motherboard and its BIOS, so you take a few other options in dealing with a troublesome CPU. One of the things you can try is increasing the CPU voltage. That will ofttimes stabilize a CPU in Prime95. Unfortunately, it also heats upwards your CPU and tin can shorten its lifespan. In fact, if you overvolt your CPU too much, y'all tin can easily destroy it. You tin also try reducing the speed of the CPU. Front end side charabanc frequencies, CPU multipliers, retention ratios, and that sort of thing are across the scope of this page. Only if you lot've been overclocking, you know what to do. Back off a bit on your overclock or (GASP!) underclock and see if that fixes your Prime95 problem. People also occasionally tin solve a Prime95 problem by overvolting or slowing downwardly their RAM. That's non very mutual if the machine tin pass MemTest86 only it's been known to happen. If you're running out of ideas then give it a try.
Ane of the less common reasons that Prime95 fails is an overtaxed power supply. Most programs barely stress a modern CPU. Web browers, word processors, and even near games don't run the CPU at 100%. And when they do, it's intermittently. There just aren't that many programs which push the CPU to 100% utilization and keep it there for long periods. When you exercise that, the power supply heats upwards. When some power supplies are pushed too hard, their voltages droop. That usually causes the computer to crash or hang although occasionally it tin can only cause errors. With any CPU made in the last few years, the CPU power comes from the 12 volt rail of your power supply. If you take a fairly powerful video card made in the final few years, and so it also draws near of its power from the 12 volt rail. A powerful video card draws much more than power in 3D mode (most games) than when in 2D fashion (web browsers and word processors). If your computer tin run 3D games on a high-end video card without crashing then you probably don't have a power supply problem with the 12 volt rail and it is unlikely to be causing problems for Prime95. Merely if y'all just run obviously old non-3D Windows programs or have a very low-end video system, then your 12 volt rail may be under maximum stress when running Prime95. In that case, you tin can probably check the 12 volt rails of your ability supply with a motherboard monitoring program. If you meet the 12 volt runway drop when you start Prime95, then that's not a good sign. Co-ordinate to specifications, the 12 volt rail should always be 12 volts plus or minus five per centum which means from xi.4 to 12.6 volts. Merely y'all actually don't want to exist on the extremes of that range. Fifty-fifty if the 12 volt rail droops, the power supply is non necessarily responsible for your issues. It's just a possibility and there's no like shooting fish in a barrel way to be sure without replacing information technology. Weak power supplies are rarely responsible for Prime95 problems, simply it happens frequently enough that you lot should consider it if you have exhausted all the other possibilities.
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How Do You Know if Prime95 Fails
Source: http://www.playtool.com/pages/prime95/prime95.html
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