Question ram compatibility makes me doubt my knowledge

[Pennyscratcher]

Hello.

First thanks for your time and knowledge.

(Sorry for the lenght. Sorry if I break any forum rule).

As to the question to solve my multiple issues well:
¿What exactly is memory compatibility as the rule of thumb to follow for what should work?

(The web is full of explanations that here and there refute each other.
Standardization should be that the type A module goes in the type A socket. Why is the mobo so picky?
The fine print: Is it the CPU FSB clock, the mobo volt current, the density, amount or design of ram chips in the module, maker...)

>User case: To revive old CPUs I bought some ram because I wanted to use virtual Android emulators and open multiple applications:

PC1)
CELERON E3400 CPU 2.6 GH and
MOBO ASUS G41MT-S2 rev 1.3
Currently (many years already) using 2x2 GB DDR 3CORSAIR 1333 RAM sticks. VS2GB1333D3.

PC2)
Core 2 Duo Processor E4500 CPU 2.2 GHZ and
MOBO ASUS P5G41T MLX
Currently (3 years already) using 2x2 GB DDR3 CORSAIR 1600 sticks. XMS3 CMX4GX3M2A1600C9 (9-9-9-24 1.65v VER2.12) Note: 1600!!!!
Homework: Checked both mobos are advertised to run 1333 (O.C.)
(What does "O.C" mean to the manufacturer, because for me everything worked PNP auto mode. I never manually enabled extreme profile, overclocked or adjusted timings).

Both mobos have dead button batterys and hardly could have stored any special BIOS config. that could now be gone.
(When I put down the automatic light circuit breakers down the clock and any setting is forgotten and for the first power-on I have to manually go into bios, load optimal defaults all auto and save and exit ).

I always thought:
- O.S 64 has no 4 GB ram limit like 32 bits had.
- Pin count of DDR3 lets you put any DDR3 module in its socket.
- The amount of RAM you can physically put in a mobo is limited only to the available module sizes of 4, 8, 16, 32 GB and free slots: 2.
- If RAM has more speed (1600 MHZ) than MOBO (1066) it will run to the lowest MHZ speed (1066) and auto adjust.
- If MOBO has 1,5 V it will burn any DDR3L 1,35v low voltage ram. If RAM voltage is 1.65v it might not get enough power and not work at all.

Problem A)
I went ahead and bought KVR16N11/8 2x8GBx1600 modules. Problem its a no go. No image, monitor goes out. Everything spins and after a while it shuts down.
Of course, I opened a box and a sticker seal to test the module, so I hope the store policies will allow me to
exchange them for 2x8x1333MHZ Kingston modules.

The thing is, I'm starting to be afraid that they won't work either. I can't abuse the store's goodwill changing multiple times.

Replacement possibilities announced in the store:
2x DDR3 4Gb 1333MHz PC3-10600 Memory Ram Kingston KVR1333D3N9/4G (going from 4 to 8 GB does not sound like multitasking for me).
2x DDR3 8Gb 1333Mhz Memory RAM PC Kingston PC3-10600 KVR1333D3N9/8G (hopefully i really want 16GB to work).

Aditional tests:
I dug up KVR13N9S8/4 1,5V 2x4GBx1333 modules. No go, same black screen. (Thinking about any 8GB mobo limit).
I dug up KCP3 16ND8/8 1x8GBx1600 module. No go, same black screen. (Testing other model same brand).
I dug up MT8JTF5126 ...... 1x4GBx1600 PC3 12800U-11-11-A1 module. No go, same black screen. (Testing another brand).
After all tests I inserted the modules it first had back and it works ok.

Problem B)
On PC2 I removed the memory modules to get a good look at the model, as the heatsink casing obstructed the view.
Tested some other ram modules in it. Also no go, same black screen.
After all tests I inserted the modules it first had back and they do not work anymore. Black screen.
No burnt smell or whatever. What could have happened...

Aditional tests:
Tried dimmA slot, then dimmB slot, then both modules, always heard the perfect insertion click sound.

Thats it.

PC are living creatures, somedays they go, somedays they dont. Have a nice day.

 

[35below0]

"If RAM has more speed (1600 MHZ) than MOBO (1066) it will run to the lowest MHZ speed (1066) and auto adjust."
It will not. It will use whatever safe speed the controller can use as a fallback. IF the controller is even able to do this. Sometimes it just gives up and the RAM doesn't work. It also may run at 1066, of course but it's not a given.


The motherboard manual might explicitly state what the fallback speeds are, and also what kind of limits there are to using RAM kits in various slots.

The manual, or motherboard memory compatibility list might state which memory kits are guaranteed to work.

...except that would not explain problem B) at all.
You can try clearing CMOS for PC2, see if it restores things.

 

[Pennyscratcher]

Problem A)
I went to the store with the PC1 (MOBO ASUS G41MT-S2 rev 1.3)
I tested there a Kingston 1x8GBx1333 MHZ module that also did NOT work.
However 2x4GBx1333 MHZ of the same model type DID work.

O.S. and processor and G41 chipset have 16 gb tolerance. So there truly is an introduced mobo max memory amount limitation of 8 GB.
I conclude it's a business strategy of product differentiation. (Somehow limit the HW by artificial means).

It's strange that the KVR13N9S8/4 1.5V 2x4GBx1333 modules I had didn't work.
So there is still this unknown RAM chip compatibility to demystify.

Im not very happy with 8 GB but its better than 4 GB so this issue is finished.

Now problem B) is still remaining.
I erased the CMOS for PC2 and it still doesn't work. I know the RAM modules are over spec, but they were working for years. How was this feat achieved ... idk.

I wonder if it will make a difference by not pressing the power supply switch (just turning off the PC's power button where the Mobo keeps a small green diode on) and thus testing the memory modules in a special order.

But now I can simply put the old 2x2 GB DDR 3CORSAIR 1333 RAM memories that are now left over from PC1 and forget about messing with the 2x2 GB DDR3 CORSAIR XMS3 1600MHZ RAM memories that were there before.

Summarizing:
The unknown compatibility of the RAM chip is a case-by-case matter and only by running tests with a wide variety of inputs (difficult for an individual to have) can it be resolved. The overexertion being only reasonable for research purposes.

One thing is clear, with money you can buy the latest fashion and forget about compatibility.


TY. 35below0. (Issues solved)

 

[35below0]

Now problem B) is still remaining.
I erased the CMOS for PC2 and it still doesn't work. I know the RAM modules are over spec, but they were working for years. How was this feat achieved ... idk.

My head is not working at the moment. I am really curious as to why PC2 decided to reject the RAM that was in there for 3 years.

Probably some boring answer.

PC1)
CELERON E3400 CPU 2.6 GH and
MOBO ASUS G41MT-S2 rev 1.3
Currently (many years already) using 2x2 GB DDR 3CORSAIR 1333 RAM sticks. VS2GB1333D3.

There's something wrong here. There is a G41MT-S2 rev 1.3 motherboard, but it's a Gigabyte model, not an ASUS.
Presumably this is a mistake on your part?

The motherboard is a small and cheaper model, indeed limited to 8Gb. The best you could have is 2x4Gb 1333 RAM that the store provided.
Mobo specs - https://www.gigabyte.com/Motherboard/GA-G41MT-S2-rev-13/sp#sp

The PC2 mobo has the same limitation, but the manual kindly includes a memory QVL. So if you like, you can stick a 2x4 1333 kit into it.
The manual is here - https://www.asus.com/us/supportonly/p5g41t-m lx/helpdesk_manual/

Of course, an unlisted 2x2 1600 can work at some lower speed, and should continue to work. I'm baffled as to why your old Corsair stopped.
Do you know if the person who installed it made some comments or some BIOS settings?

Glad i could help in some small way. Wasn't much.