Maximum RAM supported by MacOS Sierra?

There is a hard-limit, OS X before was 96GB of PHYSICAL MEMORY. However, as nbritton mentions, there are macs capable of registering more than 96GB.

I have this same question too.

What is the actual maximum that Mac OS Sierra allows? (Physical memory here folks, if you say unlimited you don't know what you're talking about or understand the question properly.)

As a 64 bit OS, it can, as Allan Eckert already noted, theoretically address 256 terabytes of memory with current Intel chip set.

The limit, as is the same with all computers, is how much RAM the overall hardware design allows access to.

In defense I've read this too. 96B of physical RAM will be "seen" in the last three or four iterations of OS X 64 bit on a system with 128GB RAM

but if you are running Win7 pro on that same Mac by booting directly a version of windows that will address it will "see" 128GB RAM

my understanding is this is a hardware limit, not a software one.

Just for giggles, I did a quick calculation. If you could actually build a computer that could hold the full theoretical 256 TB limit a 64 OS could access and using 128GB sticks of RAM to fill it, you'd need 7,812,500,000 of 'em. So assume your computer would be the size of a grocery store filled top to bottom and side to side with memory boards.

How did you calculate your final figure? Four RAM sticks of 256 Gigabytes of RAM on each stick will give you one Terabyte of RAM. Hence, 256 Terabytes of RAM would need 4 x 256 of the same RAM sticks, thus 1024 sticks, ie just two dozen more than a thousand sticks each of 256 GB of RAM. If you had rows of ten sticks by ten sticks, then the array would need to be ten levels high. A sizeable box, but hardly a whole grocery store.

And you are right! Somewhere in there, I figured far too many zeros to divide into, or not enough for the divisor.

So 1024 of the 256 GB sticks, or 2048 of the 128 GB variety.

But the issue remains the same. It's how many sticks the system/main board is designed to hold, and what the memory controller can access.

Module size and maximum memory depends on which system you have.

For upgrades, see > https://eshop.macsales.com/shop/memory/Mac-Pro-Memory

Addtionally see the special notes, because some configurations can not be mixed with other modules including the factory supplied modules.

It is the hardware that limited the maximum memory and not the OS X or macOS.

see > What is the maximum memory limit in El Capitan?

nbritton wrote:

Did they bump up the maximum memory (RAM) limit for MacOS Sierra? Last I knew it was capped at 128GB. In Lion the limit was 96GB and in Mavericks it was raised to 128GB. I'm wondering if the limit was raised again in Yosemite, El Capitan, or Sierra.

Such low limits have never existed. OS X has always had a maximum addressable memory limit of about 18 EB (approximately 18,000,000,000 GB).

That makes no difference to the operating system, which is the essence of your question. Hardware differences are a function of the Mac's hardware, and that is a different question.

FWIW, it's at least 128GBs because there are users running Mac Pros with Sierra with 128GBs of RAM.

As far as some arbitrary limit imposed by Sierra, I have no idea.

Theoretical limit for Mac with current Intel chip set is 256 terabytes of memory.

Allan Eckert wrote:

Theoretical limit for Mac with current Intel chip set is 256 terabytes of memory.

Which will need a field full of slots.