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HP Recommended

Regarding model LJ449AV  HP Z420 workstation.

I know the memory should be DDR3 UDIMM unbuffered ECC (mine 12800 1600MHz)

Is the correct voltage 1.35 or 1.5 volts?

one memory stick is marked (others not checked) The  first "K" i.e.MT9"K" signifies 1.35v

2GB 1RX8 PC3L-12800E11-13-D1
SER NO 9N141400ALO
PART NO 662608-571

by checking on websites I find this is 1.35 volts (all other HP requirements met) BUT has the correct part been fitted before I purchased this PC? if I knew the HP part number I could work this out for myself but I cannot find that out on the HP site.


Is there a way to find the correct volt by checking in the BIOS?


I know the memory stick is by Micron


Thanks in advance


HP Recommended

Hi, David:


The HP Quickspecs indicate the supported memory is DDR3 (1.5V).


ManualsLib - Makes it easy to find manuals online! (speyfy.com)


The parts list for your PC's product number indicates the memory is DDR3 (1.5).


HP PartSurfer


But here's the nice thing about DDR3L-1.35V memory...


In order to meet the DDR3 memory standard, DDR3L memory has to be able to run at both 1.5V and 1.35V.


DDR3 (1.5V) memory does not run at 1.35V.


So, it is a win-win situation if you install DDR3L memory in a PC that requires DDR3 1.5V memory.


That is why the 1.35V ECC memory is working in your PC.

HP Recommended


Your pointer to ManualsLib was perfect I just searched for "Z420", the memory loading schedule in the spec showed that the present memory was all mixed up and configuration not supported. The PC was fitted with both 2GB and 4GB sticks together. (6 sticks total, whilst no configuration uses 6 sticks and no configuration mixes different sizes of memory stick [only 2gb or only 4GB or only 8GB allowed i.e. no mixing])

The PC system information showed



the case DIMM 'slot loading' diagram indicated 'loading slot 5' and 'loading slot 7' were unused.

is this a good move?is this a good move? 

The PC is WORKING and all memory is of correct type PC3L and thus acceptable voltage, would it be a good idea to move one of the 4GB sticks from 'slot load order 8' to 'slot load order 5' to make the best of a poor job by balancing each side? I can't afford to throw any memory away!

Or do you have another suggestion using my available memory?

Best regards


HP Recommended

Hi, David:


That's quite a matrix there.


After reviewing the matrix and looking at your proposed suggestion to balance out the memory, it appears that the 242--242 configuration would work, since slots 7 and 8 get populated last according to the way I read it.


My HP and Dell business desktop PC's only have four memory slots, so it is pretty easy to place the memory correctly which is installing the same capacity of memory by skipping slots.


For example:  If I had 2 x 2 GB chips and 2 x 4 GB chips, I would be installing them 4242 or 2424, not 4422 or 2244


Naturally, it is easy when you have memory chips having all the same capacity.


The nice thing is usually if you place the memory in such a manner that the PC doesn't like it, the PC will beep 5 times at you when you turn it on.





HP Recommended

Hi Paul,


Paul with your help (about voltages and ManualLib) I eventually got to the correct HP Manual and I can now advise my final memory layout and why.

The HPZ420 using E5-1650 processor has 8 memory slots and using the recommended stick load order puts the sticks in the DIMM positions in this order DIMM number 1,8,3,6,2,7,4,5 (means put 1st stick in DIMM slot position 1, 2nd stick in DIMM slot position 8 etc etc, the board DIMM slots are numbered DIMM1-DIMM8).


The HPZ420 Manual recommends using up to 8GB sticks preferably all the same size.

BUT IF DIFFERENT SIZED STICKS then load the biggest first progressing down to smallest.


So when I look at the final position of my DIMMS (using my final stick sizes (I just purchased two 8Gb) = 8,8,4,4,2,2,2,2 GB)


I see DIMM slot number as marked on board 1,2,3,4,5,6,7,8

DIMM size are placed like this____________8,2,4,2,2,4,2,8 GB


So I now have 32GB of DIMM fitted and tested using the "userbenchmark" site which shows the memory has good performance.


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