4 JEDEC RAM vs a 3 JEDEC + 1XMP...which is better?

Question

I have upgraded my RAM, but dont understand the difference between the CPU-Z specs. My PC came with 8GB of PC3-12800. I upgraded to 32GB, but I am curious whether my new RAM is as good/better?

The spec sheet for the original RAM states that it has CL=11 timings, while the new RAM I purchased is marketed as CL=9.

As far as I know, the motherboard I have (Dell Lynx x87 I think) does not have the ability to enable XMP (Or at least I cant find this in the BIOS.

SO my question is: Is my new RAM better than my old? AND Should I replace the OLD and go up to 32GB or should I keep the OLD and just add 1 pair of Dimms to go up to 24GB?

The following are the CPU-Z specs for each of the 2 different modules. I do not know the difference between a 4 JEDEC module and a 3 JEDEC + 1 XMP module.

Original RAM:

New RAM:

Answer 1

Your old memory is half the size. But otherwise, it's better because it can run at the same frequency and timings as your new memory but at a lower voltage. Lower voltages mean less heat and increased reliability.

It can be quite awkward to run memory modules that are specified for different voltages. You will either have to overvoltage your older memory modules (possibly frying them or reducing their lifespan) or underclock all your memory modules to run them at a compromise voltage.

Answer 2

Is my new RAM better than my old?

Your new memory will run at an identical frequency as your old memory.

Should I replace the OLD and go up to 32GB or should I keep the OLD and just add 1 8GB module to go up to 24GB?

If you want 32GB of memory then you should use the new memory. If you want only 24GB then you should use the old memory and a single stick of the new memory. While I don't expect any problems configurations like that could pose a problem.

Please take a look at this table to understand the SPD contents for DDR3 modules. You should then look at this table for information on how XMP extends the JEDEC standard.

I upgraded to 32GB, but I am curious whether my new RAM is as good/better?

They are both JEDEC modules so they are identical from that perspective. The 8GB modules support the XMP JEDEC extension on systems that support XMP which it sounds like your system does not so it basically just ignores that extra bytes per the documentation I provided.

A similar, Intel-developed JEDEC SPD extension for DDR3 SDRAM DIMMs. This uses bytes 176–255, which are unallocated by JEDEC, to encode higher-performance memory timings.

So your system does not even look at those bytes. So they are identical except for the default voltage. If you have confirmed the 1.5 v modules will work in your system, and it will POST, you can use either module and your system will treat them identically because they run at identical frequencies.

Sources:

Extreme Memory Profile (XMP)

Serial presence detect (SPD)

DDR3 - SPD Contents

Answer 3

XMP is Intel proprietary extension to JEDEC memory timing data. The XMP data typically contains timing data that may work with the chip (XMP is officially overclocking so it's not guaranteed to work) and JEDEC data contains the data that is guaranteed to work.

Other manufacturers (e.g. AMD motherboards) may be able to read XMP data, too, but they cannot call it XMP because XMP is trademark owned by Intel. AMD trademark of the same thing is called EXPO.

When you mix RAM sticks, the BIOS will try to find common settings because many motherboards do not support running different RAM slots with different timings or voltages.

The examples you have, both share common timing 800 MHz 11-11-11-28 but your old sticks want 1.35 V and new sticks request 1.50 V so there is no shared voltage that both sticks can use.

Depending on the BIOS implementation, mixing the RAM chips may end up either not booting at all, or running both sticks with either 1.35 V or 1.50 V. If the BIOS chooses to boot with 1.35 V for both RAM slots, you'll run the new sticks with 0.15 V undervolting and the new RAM may be unstable (that is, the data stored on the sticks may be randomly modified if you're unlucky). Another option is to run both sticks at 1.50 V which is 0.15 V overvolting (about 111% of the specified voltage for the old RAM) which probably works but may shorten the lifetime of the old RAM due increased temperature during operation.

In either case, running system with two RAM sticks with different capacity will end up disabling dual channel memory access which will cut bandwidth of the RAM to half. This obviously cuts the performance of RAM bandwith limited applications in half, too. Depending on software you're running, this may or may not be important for you. Note that if you're using CPU integrated graphics, the performance of the GPU will be cut in half, too, for most purposes.

Note that not all Intel motherboards support XMP data and the BIOS may prevent setting RAM timings manually. In that case, the XMP timings are never used and the system will run with JEDEC timings (typically sacrificing at least 10% of the potential performance). Also note that some manufacturers (e.g. ASUS) will also overvolt the CPU without asking for confirmation if you enable XMP for RAM. Typically you have to tweak the BIOS settings quite a bit if you want to use XMP timings for the RAM without overclocking or overvolting the CPU.

If you can apply manual timing, using 800 MHz 11-11-11-28 and 1.40 V is probably okay for this specific example but I wouldn't run the system with such a configuration because dual channel memory access is that important for performance.