I want my HPZ640 to have 32GB of Ram, what slots do I put it in if I have a single processor? (2x16)

[danialhasZ640]

I need help with which slots to put my HPZ640 16gb ram stick to upgrade from 16gb to 32gb, because I have notiiced that my computer needs more ram because its using about 70-80% when I used CapCut. If anyone has any answers for which slots to install for 2x16gb to have a dual-channel mode, that would be very helpful because I'm not extremely expearienced in my HP Z640 but I tried reading the mannual but I couldn't find anything useful on there.

[DGroves]

this forum has a "SEARCH" feature where you can search for previous posts related to yours and see the answers' using this forums search can provide a useful answer in many cases 

for a single cpu you would install the two 16gb dimms in the two slots furthest from the cpu    

example-  0= 16gb dimm  x= no dimm

 0  x  cpu  x  0  = dual channel 32gb 

0=16gb dimm    x=8gb dimm  CPU  x=8gb dimm  0=16gb dimm = 48gb dual channel

From a previous post on the z640 memory

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if you install the sec cpu riser board then you "MUST" also install the sec cpu into the riser board before the ram slots on the riser board will work

each cpu has it's own specific group of memory slots, note that you cannot mix LR (Load Reduced) ram with normal or ECC ram

https://www.crucial.com/compatible-upgrade-for/hp/hp-z640-workstation

The single processor Z640 has 4 DIMM Slots supporting up to128GB DDR4 ECC Memory.
The dual processor Z640 has 8 DIMM Slots supporting up to 256TB DDR4 Load Reduced ECC Memory.

in regards to memory/dimm banks look at the HP z 640/z620 memory table and you will see that yes you can use different memory modules as long as each bank is comprised of the same 2 memory size dimms

to use DIMMs of different sizes, load them in order of size, starting with largest and finishing

with the smallest (largest in DIMM 1, smallest in last loaded DIMM slot)

https://www.manualslib.com/manual/899901/Hp-Z440-Workstation-Series.html?page=77

The HP Z640 Workstation is a Dual Processor capable system with 4 DIMM slots per CPU.

the dimm slot load order will change depending on if you have the sec cpu riser board installed

There are two memory channels per CPU, meaning Each memory channel manages two DIMM slots

each memory channel should have the same size/speed dimm for the best results but it is possible to have two 32gb dimms in one mem channel and two 64gb dimms in the other memory channel (single cpu config Using LR Dims)

for a dual cpu system you need to duplicate the same ram config again for the second cpu's 4 dimm slots

if you install mismatched ram in the memory channels for either a single or dual cpu config  then the system will either run in single channel mode which will cripple performance or not boot at all and give a memory error

The installed CPUs determine the speed at which the memory runs. If an 1866MHz capable CPU is used in the system, the maximum speed the memory will run at is 1866MHz, regardless of the specified speed of the memory.

ONLY registered and load reduced DDR4 DIMMs are supported. DDR3 DIMMs ARE NOT SUPPORTED.

again please see the HP quickspecs (memory section) for some of the HP approved memory configurations

https://www.dectrader.com/docs/set06/492792/c04400040.html