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(Updated with content from: What exactly is the cause of RAM incompatibility?)

I have changed memory modules in computers since 1992, but this is a puzzle I have not managed to crack: Why does a NT2GC64B8HCONS-BE work in a Lenovo T410, but these will not:

  • KVR16S11S8/4
  • KTL-TP3CS/4G
  • HMT451S6AFR8A-PB

When I boot the machine, it very shortly crashes after boot. The machine is known to support 2x4GB RAM, and all 4 tested modules are known good (they work in other systems flawlessly).

I thought it might be a voltage problem, but:

  • NT2GC64B8HCONS-BE: 1.5V
  • KVR16S11S8/4: 1.5V
  • KTL-TP3CS/4G: 1.5V
  • HMT451S6AFR8A-PB: 1.35V

So that is not the problem. Also 1.35V should be backwards compatible according to this thread.

https://superuser.com/a/1252970/41337 is a pretty good resource, but it does not go into what features are backwards compatible and which features are not. E.g. RAM frequency will be negotiated to be the highest supported by both computer and RAM according to https://www.crucial.com/usa/en/support-memory-speeds-compatability It also does not cover how to tell what density a given DIMM has and how to tell if this is supported by the computer.

But the answer is decent template for the known features so far of NT2GC64B8HCONS-BE:

  • Memory technology: DDR3
  • CAS latency: ? (Isn't this part of timings below?)
  • Voltage: 1.5V (1.35V is backwards compatible)
  • Timings: ?
  • RAM frequency: Backwards compatible (1600 MHz RAM will work with 1066 MHz controllers and vice versa)
  • RAM density: This https://panoramacircle.com/2018/08/07/high-density-vs-low-density-ram-why-it-crashes-some-computers/ shows exactly the same behaviour on exactly the same machine. So this leads me to believe RAM density could be the issue. The HMT451S6AFR8A-PB has 8 chips and says 1Rx8, while NT2GC64B8HCONS-BE has 16 chips and says 2Rx8.

And T410:

  • RAM controller: Supports 4G DIMMs
  • Chipset technology: ?

What feature does NT2GC64B8HCONS-BE have, that the other three don’t? And how can I tell if other 4G modules will be compatible?

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    I don't think that this is the right stackexchange page to ask. The answer will most likely bases on physics, electrical engineering (behavior of capacitors, ...) and mathematics (probability of some effects and their impact) - and it won't be easy to understand... – Robert Nov 5 '19 at 19:35
  • To me — based on a superficial scanning of specs — this seems like you are trying to place 1600MHz RAM in a machine that can only handle 1066MHz. – JakeGould Nov 5 '19 at 19:39
  • @JakeGould According to my experience and crucial.com/usa/en/support-memory-speeds-compatability "Memory is designed to be backward compatible within its generation, so generally speaking, you can safely add faster memory to a computer that was designed to run slower memory." – Ole Tange Nov 5 '19 at 22:48
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    @Ramhound But the goal is NOT to have faster memory. The goal is to have MORE memory (the modules I have just happen to be faster). The question is not about performance, but about compatibility. – Ole Tange Nov 5 '19 at 23:28
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    You need to post the CPU-Z "memory" results for each stick of memory. – cybernard Nov 6 '19 at 1:02
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Here are readout from CPU-Z.

Actual memory timings [Actual timings

memory ratings

Above is an example of timings on memory if the timings are incompatible the chip will not work together. By compatible the slowest(highest) timing for each category wins.

For example pretend you have memory chips with the following CL 18,19,20, and 21 now all chips have to be run at CL 21. Ditto for all the other settings. Also note some bios actually have dozens of timings for RAM, so if those values also have to be checked.

  • In my case there is only one DIMM in the system. Do we have actual documented examples (not just in theory) where the timing caused a system to reject the only DIMM in the system? – Ole Tange Nov 6 '19 at 8:31
  • I have had cases where I put a stick of say 1800 memory in for testing and had to manually adjust the bios for this. Then took that out and put in 1000, and because the bios didn't have auto detect it went hay wire. I forgot to set the timings back to the slower values. Any time the values are too far from what the BIOS expects there will be memory corruption, even with 1 stick of memory. – cybernard Nov 6 '19 at 12:50

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