CPU memory vs motherboard memory...?

[WarByrd]

CPU max memory is 128gb, motherboard supports 256gb... i need a clear explanation - does the CPU at 128gb mean that it will only be able to use that much data out of 256gb installed? Or am i missing something?

[Jurrunio]

It just means the CPU isnt verified to recognize over 128GB combined capacity of sticks, and when it doesnt it wont be able to boot. There's still a chance that it would work

[Bombastinator]

27 minutes ago, WarByrd said:

CPU max memory is 128gb, motherboard supports 256gb... i need a clear explanation - does the CPU at 128gb mean that it will only be able to use that much data out of 256gb installed? Or am i missing something?

Motherboard may also take a chip that supports 256gb.  More than one kind of chip fits in a given socket.

[mariushm]

In order to get 256 GB on the motherboard, you have to use big sticks of memory, 64 GB sticks if you have 4 slots.

 

The ram sticks use lots of tiny memory chips to build that capacity, as far as I know the biggest volume produced ram chips are 16 gigabit (2 GB) so to make a 64 GB stick they'd have to use 32 such tiny chips.

Due to the design of ddr4 sticks, these chips are arranged in groups of 8 .. so it's very common to have memory controllers that support 1 group of 8 chips and 2 groups of 8 chips.  This allows ram manufacturers to make sticks using 512 MB  (512 MB x 8  = 4 GB, smallest capacity DDR4 stick), 1 GB and 2 GB tiny chips and multiples of 8 chips to make the sticks.

 

Some processors simply don't support accessing more than 2 groups of 8 sticks, the memory controller inside the cpu isn't designed to support that. Such sticks also put a heavier workload on the controller, making it consume a bit more power (inside the cpu) so even if some processors support it, they may limit themselves to maximum 2 sticks of such ram sticks, or require you to reduce the ram frequency a lot to support 4 sticks otherwise you may get too many ram errors.

as for the motherboard, the concerns are increased power consumption, you have to be able to feed those ram sticks with electricity ... as one tiny chip consumes maybe 0.25w ... it's one thing to have 8-16 chips and a total of 2-3w per stick , and another to have up to 4-5w per stick due to using 32 tiny chips

A budget mobo may have a total power budget of 15-20w for the 4 slots but a higher end board will often support even 50-100w (overkill)

 

[WarByrd]

I am building a workstation tower and have been researching the 2066 socket chip sets, and came across the 10900kf intel processor and noticed it is a dual channel, 128gb memory chip.. and i am putting in 256gb, not wanting to waste money or chips, came to see if that processor is pointless being that it will jot or can not utilize the 256gb 2399 mhz ram.

[Jurrunio]

3 hours ago, WarByrd said:

I am building a workstation tower and have been researching the 2066 socket chip sets, and came across the 10900kf intel processor and noticed it is a dual channel, 128gb memory chip.. and i am putting in 256gb, not wanting to waste money or chips, came to see if that processor is pointless being that it will jot or can not utilize the 256gb 2399 mhz ram.

The only 10900 CPU you can even use (due to socket difference) on X299 is the 10900X, others are on LGA 1200....