iMac does not boot (RAM upgrade) - Solid Light, black monitor

[cannonskate]

iMac intel core duo...

My computer had 1GB of RAM, so I just bought a 2GB RAM card. When I installed both cards together i can hear the hard drive start up and then nothing, no boot up, just a black screen and the "sleep" light is just solid. I know both cards are fine because I tested each by themselves and they both started up and worked well, its only when they are both in at the same time does it do this. also both slots work because i tested both of them! I tried to do the PRAM reset and it doesnt work, and I tried to do it with one card in and then reset and then shutdown and install the 2nd card and still nothing. Please give me some advice, i am soooo frustrated!!
Thanks!

 

[Watabou]

make sure the ram is properly seated and then try and give it a shot.

 

[cannonskate]

It is definetly seated properly, I have been trying for hours!

Right on Watabou, OBAMA IS THE MAN!

 

[Watabou]

Hmm ok. Doesn't seem like it's the iMac problem. Maybe you could try calling the store where you bought your RAM and ask them if you received the correct RAM for your paticular iMac.

And I love Obama!

 

[cannonskate]

but the thing is that both of the RAM cards work, right now i am using the one i bought, 2GB, and its great, but they only work individually, not together.

ITS SOOOO WEIRD!

 

[Cave Man]

You cannot put 4 gigs in a Core Duo iMac (or Mini, MacBook or MacBook Pro for that matter). It is based on the Calistoga chipset, not the Santa Rosa. Two gigs is its maximum.

 

[Watabou]

Ah yeah. I forgot you said yours was a Core Duo iMac. Yeah you can only put 2 Gigs of RAM since the chipset is only 32-bit and cannot support more RAM.

 

[Cave Man]

Actually, it could take 3 gigs (32 bit addressing) except that Apple, in its infinite wisdom, firmware-restricted their version of Calistoga's memory controller to 2 gigs.

 

[cannonskate]

im not putting in 4, i am putting in 3Gigs (1GB card+2GB card)....is there any way to unrestrict the firm-ware for the memory controller???

Thanks guys, seriously I really appreciate the help because I am not very knowledgeable when it comes to computers...

 

[Cave Man]

Nope, no one has determined how to patch the EFI on the Calistogas. You are stuck at 2x1 gig sticks. Any more and your iMac will not get past the memory check at power-up.

 

[cannonskate]

THOSE BASTARDS!!!!!

Well, thank you again Cave Man and Watabou!

 

[kennethkearns]

mine too

I have gone through exactly the same process as you! iMac will boot with 3 gb but not four. I have a 24 in core 2 duo 2.4 ghz model. Purchased in Feb 2008. According to this http://support.apple.com/kb/HT1423 it should take 4 gb!

Anyone know anything that could help? It is definitely seated properly and I have tried every combo of chips to see if one was bad and it is not.

Please Help!

 

[GilesM]

Well, I do not know the answer to your problem, but I can confirm that I am running an iMac purchased in November 2007, with 4GB with no problems.

 

[Cave Man]

I have gone through exactly the same process as you!

Your problem is different. You have a Santa Rosa iMac, not Calistoga.

iMac will boot with 3 gb but not four. I have a 24 in core 2 duo 2.4 ghz model. Purchased in Feb 2008.

Sounds like you have bad RAM or incorrect RAM. That iMac should take up to 6 gb.

 

[kennethkearns]

I get that my model is different, but this is the closest I have found to my issue.

the RAM cant be bad because each of the 2 GB modules work when couple with one of the original 1 GB modules (in either bay no less.) They just do not work together.

 

[erstwhilepo]

Could the issue be that he/she is running 2GB in one slot and 1GB in the other? I know on the MacBook, having an odd number of ram is not good for the system and may create problems.

 

[keatonprice]

I get that my model is different, but this is the closest I have found to my issue.

the RAM cant be bad because each of the 2 GB modules work when couple with one of the original 1 GB modules (in either bay no less.) They just do not work together.

Did you ever find a solution? I'm having the same problem with my 2008 2.4GHz MacBook. I bought 2x2GB sticks and either one will work in either bay as long as it is paired with one of the old 1GB sticks (Sys Profiler recognizes 3GB shared). But I cannot get the machine to boot up with 2x2GB sticks.

 

[Cave Man]

Your new RAM chips are incompatible, most likely because of too high of frequency. When you pair it with an OEM chip, the OEM chip forces your new chips down to the proper frequency, thus they work. You need to return your RAM chips and buy a pair that are specific for your model, such as from Other World Computing.