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Mysterious RAM issue

By Rikkitic
Jan 16, 2016
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  1. I am upgrading an Acer T690, mobo E946gz, bios r01-b4. This machine has two DDR2 RAM slots. It came to me with Acer-branded 512kb RAM modules. The computer seems to work correctly, but will only boot if an original 512kb module is in one of the slots. It recognises any additional memory and appears to use it correctly, but will not boot if an original Acer module is not present. I have tried it with 1 and 2 gb modules from other manufacturers. These work fine, also for booting, in two other test computers. There is no indication that these modules are faulty and the Acer also works fine with them, it just won't boot if they are the only RAM present. Can anyone explain what is going on here?
     
  2. cliffordcooley

    cliffordcooley TS Guardian Fighter Posts: 8,548   +2,894

    What is the speed rating of the modules? Your machine may be finicky and require a specific frequency ratings.

    According to the following link your machine requires DDR2 667 (PC2-5300).

    http://www.memorystock.com/ram/AcerE946GZRAM.html
     
  3. Rikkitic

    Rikkitic TS Rookie Topic Starter

    Thanks for the reply. The memory is all the same speed. Both the 1 and 2 gb modules are 667, as are the 512kb ones from Acer. Like I said, the machine works with them fine, but if it doesn't also see the original 512 mb module, it freezes on the splash screen. No beep, it just stops.
     
  4. cliffordcooley

    cliffordcooley TS Guardian Fighter Posts: 8,548   +2,894

    Hmm, gotta admit, I'd be grasping at straws since they are the same frequency. Does the Bios voltage match that of the new modules?
     
  5. Rikkitic

    Rikkitic TS Rookie Topic Starter

    Yeah, it's all 1.8v. I said it was mysterious. I have two 2 gb modules that have been working perfectly in another machine for years. I took one to test with. I also have a single 1 gb second-hand module I bought. Finally, there are 4 Kingston KTH-XW4300 1 gb modules I just bought used. One of those was bad but everything else has tested out fine in other computers. They all work in the Acer, except for booting. I just ran Memtest 86 on the currently installed modules and they come back clean. Everything is all hunky-dory, except none of the damned modules will boot the Acer. I'm stuck with the 512kb module I have for that, and if it stops working, so does the computer. It also takes up half the available slots. There has to be some kind of answer to this. Anyway, thanks for trying and if you think of anything else I will be grateful to hear it.
     
  6. Cycloid Torus

    Cycloid Torus TS Evangelist Posts: 1,655   +308

  7. Cycloid Torus

    Cycloid Torus TS Evangelist Posts: 1,655   +308

  8. Rikkitic

    Rikkitic TS Rookie Topic Starter

    Thanks for the links. This is getting over my head. I know something about hardware but I'm no expert. I figured any DDR2 memory that met the voltage, frequency and size specs would work. What other requirements are there? If I knew what to look for I could look for it locally. The Acer does work with my other memory modules as long as I have the one stick of Acer RAM in one of the slots. Otherwise it freezes on start-up. I haven't encountered this before and would like to learn more if anyone knows.
     
  9. Rikkitic

    Rikkitic TS Rookie Topic Starter

    I finally know what was going on. Someone on another forum explained it to me. I had just never encountered it before.

    Faster RAM will work at slower frequencies but it has to adjust on start-up. Sometimes this doesn't happen fast enough and the computer will fail to start. The one stick of RAM I had that worked, was 533 Mhz. That doesn't have to adjust because it is already the right speed. I thought some of the others I was trying also were, but when I went back and checked, that was not the case. They were all 667. This computer will work with faster RAM, but it will only start if it sees at least one 533 Mhz module. I bought some 533 Mhz RAM on-line to test this and it did indeed work. Mystery solved.

    The other mystery is why the two 'identical' machines behave differently, since the other one doesn't seem to have this sensitivity to the speed of the RAM, but I think I will let that one go. I'm just glad to have an answer to this.
     
  10. Cycloid Torus

    Cycloid Torus TS Evangelist Posts: 1,655   +308

    Yah, that kind of thing. Years ago I got messed up with some 1 MB sticks - one used 128kb chips and the other used 256kb chips - same voltage, same frequency - who knew?!?
     

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