should RAM total amount be on power of 2?

[HingedEmu2]

hi,
i asked myself many times if the total RAM amount in computer should be in power of two- 2,4,8,16... like a singel ram device.

i didnt find answer.
ill be glad if you will be able to answer me and explain.

HingedEmu2.

 

[ericloewe]

Not really.

However, most systems work best in dual or quad channel mode, which tends to mean identical memory modules. Since they only come in powers of 2, you'll end up with a power of 2 amount.

Triple channel is somewhat different, but can still be expressed as 3*2^x.

Just make sure you're using a kit (2, 3 or 4 modules) and you'll be fine.

 

[imagoon]

The power of 2 rule is from the JEDEC / SPD standards. This is only per module and in theory there is no reason why 11GB of RAM would not work since the computer addresses each module of RAM.

It is currently based on the SPD value for the sizes of the RAM modules on the memory card where they follow a rule like:

00h = 256mbit
01h = 512mbit
02h = 1024mbit

 

[_Rick_]

On my first 386 there were 1664kB of RAM installed.
So even back then, there was no problem with non-power-of-two setups.

On the other hand, there's rarely a (computing) reason not to install memory in powers of two.

 

[lehtv]

If running dual channel, you can still have 2x2GB+2x1GB = 6GB, or 2x4GB+2x1GB = 10GB, or 2x4GB+2x2GB = 12GB, etc.

 

[BurnItDwn]

I run 1024 + 256 +128 for 1408MB on an old server I have at home. It came with 128MB years and years ago, and I've added more over the years to meet my needs. I'm at the point now where I'd like to add another GB, but at this point, the machine is so old that it's probably time to simply replace it with a new one...

 

[imagoon]

The OP never came back but I think he meant a single device like a RAM module. I doubt there would ever be a reason make 1408MB RAM modules or anything. I do know on a per module basis, DDR3 requires base 2 because of the standard for the SPD data. In the future "12GB" modules might be ok though.

 

[dave_the_nerd]

:ulls DIMM from desktop for 5GB of RAM, just to confuse tech support::

 

[Insert_Nickname]

If running dual channel, you can still have 2x2GB+2x1GB = 6GB, or 2x4GB+2x1GB = 10GB, or 2x4GB+2x2GB = 12GB, etc.

Yes, its possible but you will end op with a "faster" and "slower" half of the RAM. Only the lowest capacity is mapped for dual-channel operation... :whiste:

That assumes you run a 128bit interface, if you run a single 64bit channel, no problem... though you can run into problems with more then two DIMMs per channel...

 

[BurnItDwn]

The OP never came back but I think he meant a single device like a RAM module. I doubt there would ever be a reason make 1408MB RAM modules or anything. I do know on a per module basis, DDR3 requires base 2 because of the standard for the SPD data. In the future "12GB" modules might be ok though.

Yea, probably ... 1408 is a bizarre amount of ram, only reason why I mentioned it

Sad thing is, because it's DDR1 Buffered ECC, it costs more for a 1GB module than some 8GB modules of DDr3