[SOLVED] Are my two 4GB Hynix RAM sticks near identical?

[Frooby]

I recently bought these two DIMM sticks - second hand - from the same supplier, assuming they'd be a near matched pair.

One is PC3-12800U-11-12-B1 and the other is PC3-12800U-11-11-B1. What difference is signified by the 11 and 12, please?!

Thanks.

(And please don't groan too loudly at what must be a simple Q... :-( )

 

[Darkbreeze]

Groan.

Ok, just kidding.

No, they are not even remotely similar. Even if they were the same part number but came from different production runs, they might not be.


Well, here's my typical canned response to those types of issues, and while it IS sort of generic, it really is true.

Anytime you plan to use more than one module, for dual, triple or quad channel operation, is is ALWAYS a good idea to buy them in a matched, tested set that is already known to work together. Even buying IDENTICAL part numbers is no guarantee that any two modules will work together because there are so many variables involved. Usually there is some room for compatibility differences, but a LOT of the time, more and more as time goes on and systems become more specifically finicky to differences in hardware, there is not.

Modules with the part number XXXX this week might use different memory chips, from a different chip supplier, with different numbers of chips or not even having the same number of sides containing chips, then the same XXXX part number that came from a different batch of chips next month. That means they may or may not work together in multiple channel configurations, or at all.

In some cases, even modules that came off the exact same production run but were not tested to be compatible with each other before they were packaged up and sent out, ie, bought separately NOT in the same package together, might not be compatible. I've seen this MANY times where somebody buys two packages of the same module, rather than one package with two modules in it, and they would not work together although each module worked fine individually. It is NOT uncommon. It is also NOT in every case.

Sometimes you can slap two totally different modules in together that are not even the same speed, voltage or latency and they will simply work. Often though this is not the case. It is ALWAYS a crap shoot unless you buy them together and even THEN sometimes it still happens, but a LOT less frequently than when bought separately. For examples of this you can check out this thread here where I provide specific examples of how modules that are even the same model and part number, are hugely different.


http://www.tomshardware.com/answers/id-3610013/amd-ram-compatibility.html#20562100

 

[Frooby]

Thanks Darkbreeze.

I do understand the idea of 'matched pairs' - sticks made from the same batch of chips, etc - and how this is clearly desirable for maximising performance and reliable operation.

This isn't essential for me on my PC which is used for general domestic stuff and surfing, but it's what I'd obviously aim for given the choice (which is what I'd hoped for in this case...)

My two sticks are clearly not 'matched', and that I can live with as long as they work. However, I was wondering just how 'unmatched' they were to each other by reference to these label numbers.

They are both 1600Hz and all that gubbins, I believe. Are they 'badly' different?! What do these numbers refer to?

Thanks.

 

[Darkbreeze]

Those numbers you posted are specifications, not model numbers. You'd need to get the actual model numbers to really try to determine anything concrete. Either model or part number. Those numbers are neither.

 

[Frooby]

Those numbers you posted are specifications, not model numbers. You'd need to get the actual model numbers to really try to determine anything concrete. Either model or part number. Those numbers are neither.

Both have HMT351U6CFR8C-PB NO AA and after this one has 1309 and t'other 1237.

I know they are not 'matched', but are they effectively the same spec? Ie - if they work, then presumably they'll work 'fine'?!

A bit concerned by Darkbreeze's "No, they are not even remotely similar."

In my basic computing world, whenever I've upgraded RAM in a PC, I'd buy a similarly spec'd stick (RAM size and speed, that sort of stuff) and stick it in the spare slot. It has always 'worked'.

Cheers.

 

[Darkbreeze]

No they are not remotely similar is in terms of "these are not the same sticks because they are not tested together". As I said, it matters not whether they have identical part numbers or are from an entirely different manufacturer. If they are not matched and tested sticks, verified from the manufacturer for compatibility, then they could have just as much chance of working together whether they are two totally different speeds and brands with different timings as they do with same part number but from different production runs.

To clarify further, my statement does not, in any way, mean that they cannot work together, but also equally important is the fact that no matter how similar they might SEEM on paper, it's still no guarantee AT ALL that they will play nice together. I've seen people order five or six different sticks trying to get any one of them, that are identical part numbers, to work together with one random DIMM they purchased originally sometime previously. And then I've seen people stick DIMMs that are hundreds of Mhz apart in terms of advertised speed and wildly different timings, together, and have them run easily with no problems at all, albeit at the speed of the slower stick.

On your sticks, the PB, or an H9 or RD are the identifying digits that determine different parts.

https://www.skhynix.com/eolproducts.view.do?pronm=DDR3+SDRAM&srnm=HMT351U6CFR8C&rk=20&rc=module


So those sticks, if they both carry the PB designation are both 1600mhz with 11-11-11 timings according to the information on the manufacturers product page I linked to above.

If the information YOU are seeing, indicating some form of 11-12-12 or 11-11-12 timing on the other set, is probably not enough OF ITSELF to cause incompatibility. The motherboard will simply try to run both at the higher 12 timing OR you can manually configure the timings so that both sticks carry the 11-11-11 timing and then run Memtest86 to ensure they are working correctly together and have no problems with those timings. Probably an auto setting or enabling XMP will work fine.

 

[Frooby]

Thanks. I get what you are saying, and I appreciate the detail you have gone in to.

Cheers.