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Windows 7: Prime95 - Rounding was 0.5 expected less than 0.4

13 Jan 2012   #1

Windows 7 64 Ultimate
Prime95 - Rounding was 0.5 expected less than 0.4

So I am having problems with my hardware causing hard locks on my PC, where only a manual shutdown will help.

I did everything software related until I figured out it was hardware when it froze when reinstalling windows and when it froze on memtest also.

I switched the GPU and it worked for 3 hours so I believed a RMA would solve it. When I had the RMA approved, just to make sure, I tested my system with another video card again and started memtest. It froze several times, so it could not be the GPU causing it.

I then managed to run prime95 for over 8 hours and one of the worker threads stopped after 6-7 hours with error "FATAL ERROR: Rounding was 0.5 expected less than 0.4". Searching the web, it seems that this is a memory issue and that it can be caused by a a faulty unit, wrong voltages and/or timings amongst other things. Now I did notice that my mobo(latest BIOS) wasn't setting my memory timings and frequency correctly and I had to set it manually.

So I came here to ask something. Since the error happened in Prime95, what would happen if this was caused outside it? Would it lead to a hard lock on my system? If it did, then this error is definatly related to the hard freezes I get on my system, that can help once every 2 days, or 3 times in 1 hour. It's really random and unpredictable and the only way I can make it occur faster is by running memtest or Windows memory diagnostic tool.

The strange thing is that I never get a BSOD. It always freezes. It is not a bad PSU as I have checked all voltages and they are all perfectly fine.

System specs -

PSU: FSP Aurum Gold 700 (very good PSU)
CPU: I7 2600
GPU: GTX 570
RAM: Hyperx 1600 (2x4gb)
Mobo: ASUS P8P67 PRO

My System SpecsSystem Spec
13 Jan 2012   #2
Microsoft MVP

Windows 7 Ult. x64


A few things to consider:

1. What size is your pagefile?
2. Are you overclocking any of your components?
3. Run Memtest86+ for a minimum of 7 passes, or until you get errors from a bootable DVD or USB. This will test for defective RAM chips or RAM motherboard slots.

Memtest86+ - Advanced Memory Diagnostic Tool

My System SpecsSystem Spec
13 Jan 2012   #3
Microsoft MVP


Here's an old discussion that I had about Prime95:
DRAFT Prime95 testing procedure
This is in case you are getting errors in Prime95 and want to nail down the cause

Run HDD diag and MemTest prior to Prime95

Run Blend test - log the time that it took to error (or not, as the case may be)
Run Inplace Large FFT's test - log the time that it took to error (or not, as the case may be)
Run Small FFT's test - log the time that it took to error (or not, as the case may be)

Run CPU Stress Tests
- 7Byte : Hot CPU Tester Pro
- 7Byte : BurnIn64
- CPU Stress test
- Fossil Free Online CPU Load or Stress Test.
- CPU Stability Test description, System Resources Tune-Up. Downloads List By All Time Popularity | PCWorld | PCWorld
- CPU Stress test
- |MG| CPU Stability Test 6.0 Download
- LinX - A simple Linpack interface

Run Video Stress Tests
- FurMark: VGA Stress Test, Graphics Card and GPU Stability Test, Burn-in Test, OpenGL Benchmark and GPU Temperature | oZone3D.Net
- МИ NVIDIA / Утилиты / VMT
- МИ NVIDIA / Утилиты / Artifact Locator

Swap RAM sticks around per Steps 7 through 10 of this link and run Prime95 (in Blend mode) on each stick/slot: Memory Diagnostics
This is because of issues found in this topic:
Small FFT's test CPU cache and very little memory.
Large FFT's access' a lot of memory - but in-place option keeps it limited
Blend is not run in-place, so it cycles the tests through a lot of RAM

All tests stress the CPU
In-place large FFT's and Blend also test CPU/RAM interface (mobo in all but Athlon64 and Intel i-series)
- This would then be testing the memory controller onboard the CPU in the Athlon64 and i-series processors
In-place large FFT's stress CPU more than Blend
MemTest is better at testing RAM

Prime 95 tests 3 things:
- Memory
- CPU/RAM interface (mobo in all but Athlon64 and Intel i-series)

FWIW - the distinction between RAM and different types of memory in the system is one that I've made. The documentation that I've read speaks of RAM issues and CPU cache - and doesn't mention the other aspects. BUT, this is just speculation on my part, so we'll have to see how it works for us.
Link to explanation about i-series CPU/RAM interface: Intel Core - Wikipedia, the free encyclopedia
Common features of all Nehalem based processors include an integrated DDR3 memory controller as well as QuickPath Interconnect or PCI Express and Direct Media Interface on the processor replacing the aging quad-pumped Front Side Bus used in all earlier Core processors.
In short, if you're running the Blend test, the error is most likely in the RAM
But you have to run all 3 tests (Blend, Large FFT's, and Small FFT's) in order to figure out what's wrong.
Make sure that you know which one spits out errors first (fastest) and which one spits out errors slowest (or doesn't spit errors). That way we can figure out what's most likley (RAM, CPU, mobo).

Also, include the make and model of your CPU and your mobo. There are differences in how memory is handled in some CPU's and mobo's - so it makes interpreting the results a bit harder.

Good luck!
My System SpecsSystem Spec

13 Jan 2012   #4

Windows 7 64 Ultimate

Hello, I'm not overclocking any hardware. The closest to it is that I set the frequency and timings of my RAM to the correct values according to manufacturer since BIOS(latest version) did it incorrectly.

The problem when running Memtest is that I have seem at least 15 passes(non sequential) so far with both sticks of RAM and no errors, but it does freeze after a while. It also happens with Windows Memory Diagnostic Tool and that is why I believe there is some problem with a RAM, most likely it's voltage...

I'll try running the memory intensive module of Prime95 and see if it reports any errors. I wish I had a spare stick of RAM to test...

Edit: I'll inform you the details about CPU and Mobo when I get home. Thanks so far.
My System SpecsSystem Spec
13 Jan 2012   #5
Microsoft MVP


You have 2 sticks of RAM - run the Prime95 on each stick individually
Blend test is best for stress testing RAM.
In general, MemTest and other like it don't stress the RAM when testing.
My System SpecsSystem Spec
13 Jan 2012   #6

Windows 7 64 Ultimate

I should have told before, but I already ran memtest with each stick individually and in different slots and it always resulted in hard locking. The longest time it could run was around 45 minutes without freezing. This is why I'm avoiding Memtest as it freezes faster than anything else and never points out a single error.

Edit: It freezes in random times also, it can be 3% first pass, or 98% third pass. No pattern to follow. That's another reason why I think it is voltage issue. I'm no expert, so let me know if I'm talking crap.
My System SpecsSystem Spec
13 Jan 2012   #7

Windows 7 64 Ultimate

So I got home from work and the first thing I noticed when I navigate the BIOS is that the damn motherboard did not set up voltages for DRAM correctly as well. It states very clearly by the developer that it must work with 1.65V and it was working with 1.5 instead.

Now I have a good feeling that setting it manually may solve my problems, because things were pointing this direction and then I find it was indeed incorrect. Also, 1.65 is also stated to be a safe voltage for my processor(I7 2600).

Btw, I have attached a screenshot with more voltages. Would someone kindly analyze it and tell me if they are OK?
My System SpecsSystem Spec
13 Jan 2012   #8
Microsoft MVP


I'm no expert about voltages, I'd suggest a separate post to ask for help with them.

Make and model of Mobo and CPU please.
My System SpecsSystem Spec

 Prime95 - Rounding was 0.5 expected less than 0.4

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