three beeps after installing faster ram

friend upgraded to 16GB ram and gave me his 2 x 4GB PC3-12800S sticks to put into my imac 2.66 core 2 duo with 2 x 2GB PC3-8500 sticks. I removed my 4GB and installed the 8GB. Seated very well (well as far as I can tell anyway)

Three beeps after power on.

reinstalled the old ram and runs fine.

is this ram not compatible with my old imac?

Simple ~ wrong memory.

Macs are very fussy about memory and must have low density modules, not cheaper high density PC shop modules. Go to OWC and/or Crucial ~ Mac specialists for your memory needs. The 2008/09/10 2.66GHz iMac, last of the 2.66, use PC3-8500 modules.


http://eshop.macsales.com/shop/memory/iMac/DDR3_2009

Don't let friends do anything to your Mac if they ain't specialists. Especially PC folk who LOVE to tinker inside Macs.

so just to be clear. The 8GB was ram that came out of my friend's mac.

Mac's can't use faster memory than what it originally had? (I'm a recent toe dipper in the mac pond)

redeeps said:

so just to be clear. The 8GB was ram that came out of my friend's mac.

Mac's can't use faster memory than what it originally had? (I'm a recent toe dipper in the mac pond)

Click to expand...

Same answer as Harry mentioned...wrong ram. The three beeps is a specific alert for wrong or bad ram installed.

- Nick

redeeps said:

so just to be clear. The 8GB was ram that came out of my friend's mac.

Mac's can't use faster memory than what it originally had? (I'm a recent toe dipper in the mac pond)

Click to expand...

Just to be clear: it's nothing to do with being faster and everything to do with being DIFFERENT RAM. With rare exceptions, no Mac can use RAM that's different than the ones it shipped with (other than changes in capacity, of course).

And to make another point.... The latest Windows machines likewise can not use memory other than what the machine was designed for. So it isn't just Macs that are "fussy".

redeeps said:

Mac's can't use __faster__ memory than what it originally had? (I'm a recent toe dipper in the mac pond)

Click to expand...

Not to beat a dead horse...

The speed of memory that any computer can use is dependent on the memory bus and memory controller on the motherboard. You can't just put faster-spec memory in and expect things to be faster.

(On the other hand, "most" memory of the correct type but faster spec will be backward-compatible - ie, work at the slower speed of the memory bus. So, must be something other than just speed spec.)