Testing RAM Sticks

[MickeyD]

HP 8200 Elite SSF
Windows 10 pro 1909

I suddenly developed boot issues. The monitor stayed black but the power supply fan would run. After about a full minute, the fan would rev up to full speed and continue until I forced a shutdown.

I may have solved this problem on my own. I will post one way or the other when I know for sure. Til then, I need some help in understanding how bad RAM affects the performance of good RAM.

I searched the Internet looking for a solution to the boot issue. Most sites were in agreement that with my particular set of symptoms, more than likely, bad RAM was the cause of the problem. They suggested testing RAM before any other troubleshooting.

I have four sticks of RAM. I removed the first. There was no change in the boot issue. Leaving the first out, I removed the second stick. There was no change in the boot issue. Leaving the first and second stick out, I removed the third stick.

With only the fourth stick of RAM in place, the computer did boot normally and ran OK (although I did not test for performance or speed). I concluded the third stick was bad. While leaving it out, I replaced sticks one and two. Again, I got a normal boot.

There seems to be no doubt that the third stick is the problem. Later today, I will return the third stick to its slot. If I then get boot failure again, I can be sure the problem was due to the third stick being faulty. Right?

Here is where I need help understanding just what's going on. If I understand, I will be far less likely to forget what I have learned.

If you have four light bulbs wired together in a particular configuration and one bulb burns out, the other three will continue to burn whether the burned out bulb remains in its socket or removed and the socket left empty.

This is what I would have expected with four sticks of RAM. I now think I am wrong. It seems that leaving a bad stick of RAM in place affects the normal operation of the other three, while removing that bad stick permits the other three to operate normaly.

Am I correct in this or do I have it all wrong as to how good and bad sticks of RAM affect the performance of each other?

Thanks for any enlightenment.

[rproffitt]

Light bulbs work differently so it's not a good analogy. Maybe a chain is a better one as one bad link and the chain fails to do its job.

I've purposely not started a lesson on computer architecture here.

[MickeyD]

Perhaps I should familiarize myself with Daniweb's policy on retracting posts, if indeed there is such a policy.

[rproffitt]

No real need to do that. However you can alert it to be removed and editing is limited to the first 30 minutes (from memory.)

[rproffitt]

I need some help in understanding how bad RAM affects the performance of good RAM.

In a classic PC design the RAM shares a lot of signals. Data and address buses for example. Since a bad stick "sits" on those signal lines a bad stick can stop the PC dead. There's not much mystery here. So moving on.

1. It's well accepted we should not mix make, models, and in some cases the build lot of memory sticks.
2. Stick to what is documented by Crucial, HP (maker) for these sticks. Just because it fits does not mean it's compatible.
3. I no longer try to save or test suspect bad sticks as over the years I've run into sticks that burn up the motherboard or CPU. So at the office and shop we toss bad RAM quickly. Not worth the risk. Let those that think such is worth keeping to well, to each their own.
4. When we suspect RAM, all the sticks come out and we test one at a time.
5. When all the sticks come out we take that moment to be sure they are all the same make and model as well as inspect for issues like scorch marks.

[DGPickett]

If stick 3 runs the machine OK alone, then incompatibility is a strong possibility. However, there is usually one way things can work and an infinite number of ways they can be broken! It might be broken so it runs but messes up any and all other cards on the same bus. I recommend buying a completely identically spec'd set of ram sticks of the highest performance the cpu and motherboard support. The pairs can be of different sizes, but within the pairs they should match so they can be interlaced/channeled. Go for the max size your system supports. Parity and error correction, if supported, are nice but not required for most of us. Clean the fans, too! :D