How to Fix: Bootable Prime95 to Stress Test Hardware

Dennis Faas's picture

Infopackets Reader Peter M. writes:

" Dear Dennis,

I have a very strange issue. I recently put together a new computer build and installed Windows 10. Everything was working fine for the past month or so, then all the sudden, Windows 10 won't boot into the login screen - it simply freezes at the swirling dots. Surprisingly, I can remote desktop into the problematic machine from another, but the system stability doesn't last and eventually it freezes up on me. I suspect I have a hardware problem - perhaps the video card. I've managed to run 'msconfig' and specified Safe Mode with Networking, and I am able to get past the swirling dots and into the login screen - however, the system will eventually lock up after a duration of time. Is there any way I can test my motherboard, CPU, RAM and power supply before I order a new video card? As per your suggestion I have used Prime95 in the past but Windows does not seem to be stable. What should I do? "

My response:

Most likely it is the video card that is the culprit here based on what you are telling me. In this case I would revert a disk image backup of the operating system to ensure it is not the operating system that is faulty (or a driver for that matter).

If you don't have a disk image backup then you can always install Windows clean (providing you have a way to backup the existing system). If you get the same result from a known, good working backup or a clean install, then it is likely the video card that is causing you grief. At this point, it may still be possible to stress test the system (RAM, CPU, power supply) before ordering a new card; below I'll explain how to do that using The Ultimate Boot CD and Prime 95.

How to Fix: Bootable Prime95 to Stress Test Hardware

The Ultimate Boot CD (also known as "UBCD") runs using a Linux command prompt environment using a simple menu system. If you've never used the interface before, you likely won't know how to operate it - as such I'll provide instructions on how I go about stress testing hardware in this environment.

  1. First, download the latest version of the Ultimate Boot CD in .ISO format.
  2. Burn the .ISO file onto CD / DVD using CD Burner XP (free), for example, or use Rufus to create a USB thumb drive image if you don't want to use a CD or DVD.
  3. Boot the computer that you would like to stress test with the Ultimate Boot CD media inserted. If it does not boot from the media, then you may have to go into the BIOS and change the boot sequence such that the CD / DVD or USB thumb drive boots before the hard drive.
  4. Once the Ultimate Boot CD is loaded, you will be presented with a menu with the options: BIOS, CPU, HD, Memory, Others, and more. Use your arrow key on the keyboard to select the "CPU" menu. On the following menu, select "Mersenne Prime Test v28.x" and press Enter. It will then load Prime95, which consists of CPU intensive prime number testing. Press a key to start, then select option #2, which is: "In place FFTs (maximum heat and power consumption, some RAM tested)" and press Enter on the keyboard. This will torture-test the CPU, RAM, and also your power supply.
  5. Once the test begins you can run other tests and also a progress indicator of the system. To do so, press ALT + Right Arrow; this will present you with a blank page that says "Press a key to begin a new console". Press Enter on the keyboard to do so. You will then be presented with a command line: type in "menu" and press Enter to select more CPU menu options, such as option #7 "CPU Stress tester 2.0" which can run alongside your Prime95 test.
  6. You can open yet another console by pressing ALT + Right Arrow on the keyboard. Once you are at the command prompt, type in "top" and press Enter on the keyboard. This will show you the tasks that are running on the system, plus the CPU load. The screen will update itself every few seconds. This is a good way to see if the system is still active or not. If it is not active, then your system has crashed - if that is the case then you definitely have a hardware problem.

I would run the test for at least 24 hours if possible. If it runs fine for 24 hours then it is safe to say that your CPU, RAM and power supply are fine, which means it's most likely the video card.

Please note that if you have an overheating issue, these tests will not show the temperature of your processor or case - so please ensure you have proper ventilation, the dust has been cleared from your components, and you have proper air flow before running these tests. That said, most modern CPUs will throttle to a lower frequency if they start to overheat to avoid damaging the CPU and motherboard.

Also note that you can flip back between the running tasks by pressing ALT + Left Arrow (or right).

I hope that helps.

Update: Peter emailed me back and said that he ran the tests and the system was stable for 24 hours. He was able to borrow a video card from a friend and was able to boot into Windows without issue. Problem solved!

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I need more computer questions. If you have a computer question - or even a computer problem that needs fixing - please email me with your question so that I can write more articles like this one. I can't promise I'll respond to all the messages I receive (depending on the volume), but I'll do my best.

About the author: Dennis Faas is the owner and operator of With over 30 years of computing experience, Dennis' areas of expertise are a broad range and include PC hardware, Microsoft Windows, Linux, network administration, and virtualization. Dennis holds a Bachelors degree in Computer Science (1999) and has authored 6 books on the topics of MS Windows and PC Security. If you like the advice you received on this page, please up-vote / Like this page and share it with friends. For technical support inquiries, Dennis can be reached via Live chat online this site using the Zopim Chat service (currently located at the bottom left of the screen); optionally, you can contact Dennis through the website contact form.

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ecash's picture

I learned long ago, while building systems, and repair..\
ALWASYs have a few cheap cards..
A cheap video and audio card can solve allot of things..
SPARE keyboard and mice/trackball are Essential..
WHY have 1 fail, and you NEED ONE NOW, and take time to run out to get one...
Watch for a few sales, get 1-2 of each..NICE ONES, not FANCY..

Old wireless, ran out very quickly...NEW ones can take a YEAR to fail/run out of battery power..(FEW have a recharge stand to sit in EVERY NITE..)

When they FAIL. run out of battery power,
Its generally in the middle of a GAME or something REAL important..
KEEP a SPARE..wired and CHEAP if you need..$10-20 bucks works very well..

sytruck_8413's picture

If the board has builtin video pull the suspect card, connect to the board video and see what happens.

Dennis Faas's picture

Good suggestion - in this case there was no video on the board. He was using a Ryzen motherboard and the only video support on board is if you use an APU (non-Ryzen CPU). Also, the motherboard was extremely finicky about which video cards he could use. He had a few older cards but most would not post pass the flash screen.

ecash's picture

THAT is a pain on a new board...
HAs he run all the bios updates that have come out??

nortonproductions_10956's picture

Glad to have found this article. Been using prime95 to overclock since 1996 and somewhere along the way I forgot that windoze processes get in the way of the accuracy of prime95 - this article reminded me that there is a way to beat that fact. Top of the line information in your article, kudos sir.