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Old Jan 17, 2009, 09:29 AM   #26
jsteelm
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Theres a flaw with either the Intel chipset or the apple EFI or both. Im guessing the EFI as the Intel chipset exists in other laptops and we have not heard anything on other laptops having this issue.

Anyway, my solution was this:

*****DISCLAIMER: I take no responsibility for voiding RAM warranty or harming the computer by using this program********

Boot into bootcamp (one 800mhz ram stick one 667mhz ram stick) and use this:
http://forums.techpowerup.com/showthread.php?t=20349

Change the CAS to 3ns from 2.5ns to make the RAM 333Mhz (with dual data rate thats 666, oh but thats evil, better round up the .1 to 667)

Make sure to use the "edit change checksum" or something of the like. Just DO NOT WRITE THE DATA WITH INVALID CHECKSUM!!! You only really need to do this with 1 RAM stick as the other one will be throttled down to match the lower speed by the chipset (oh right, it works, go figure its an EFI problem).

Anyway, enjoy this hotfix until Apple fixes their proprietary hardware interface software. If you break your RAM, tough luck, complain at Apple or accept the responsibility that you didn't know what you were doing and broke it.
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Old Jun 15, 2009, 03:30 PM   #27
Strotos
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Yeah I bought some 800MHz that didnt work

Quote:
Originally Posted by CanadaRAM View Post
There is a well-known problem with 800 MHz memory not having properly written SPD values and being incompatible with Penryn Macs. So although theoretically they should clock down to 667, if they are not programmed properly, they won't work. One report is that they do work when installed one at a time with an Apple RAM in the other socket -- because the Apple RAM forces the machine to 667 CL5 timings with its correctly written SPD values. But with only 1 or 2 of the 800s it fails.

A case of false economy -- the 'faster' RAM gives you no speed benefit plus added grief.

MR Guide to Buying RAM

The other issue with MacBooks that is very common: not installing the RAM completely. When you push the RAM into the slot, it goes in about 1 inch and stops. It is not installed yet. You need to get both thumbs on the RAM and push hard, and it goes in another 1/8" or so (2mm for the eurocentric SI crowd. Here in Canada we're informally bimetric as well as legally bilingual. Or maybe that's polymetric. Can't remember)

Anyway, if you don't have dents in your thumbs, you haven't pressed hard enough.

The classic non-inserted RAM symptom is a pulsing white power light and a black LCD screen.
Best advice on The Net I have found so far. I bought 4Gigs of 800MHz Ram for my Black Macbook (2x2Gigs) so as you all know it didn't work . Been trying for awhile to get it to work. I bought it because I thought it would be clocked back to 667 but odvious it wasn't. Just wanted to say thanks for the advice and the explanation as to why it doesnt work. So 3 Gigs it is.
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Old Jun 15, 2009, 04:20 PM   #28
Strotos
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Smile It worked....

Quote:
Originally Posted by jsteelm View Post
Theres a flaw with either the Intel chipset or the apple EFI or both. Im guessing the EFI as the Intel chipset exists in other laptops and we have not heard anything on other laptops having this issue.

Anyway, my solution was this:

*****DISCLAIMER: I take no responsibility for voiding RAM warranty or harming the computer by using this program********

Boot into bootcamp (one 800mhz ram stick one 667mhz ram stick) and use this:
http://forums.techpowerup.com/showthread.php?t=20349

Change the CAS to 3ns from 2.5ns to make the RAM 333Mhz (with dual data rate thats 666, oh but thats evil, better round up the .1 to 667)

Make sure to use the "edit change checksum" or something of the like. Just DO NOT WRITE THE DATA WITH INVALID CHECKSUM!!! You only really need to do this with 1 RAM stick as the other one will be throttled down to match the lower speed by the chipset (oh right, it works, go figure its an EFI problem).

Anyway, enjoy this hotfix until Apple fixes their proprietary hardware interface software. If you break your RAM, tough luck, complain at Apple or accept the responsibility that you didn't know what you were doing and broke it.
Cheers for this, tried it and it worked great. Was a bit worried about doing it but as long as you go to "Edit" and "Fix Checksum" then write the changes back to the ram it will be fine. Great fix, thanks
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Old May 15, 2010, 03:01 PM   #29
Howard Brazee
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Join Date: Oct 2006
Location: Lafayette CO
I just put in 4G in my 3 year old iMac. I turned on my computer and it made a very short noise and stopped. So I decided to try to remove the RAM. Pulling the tab doesn't do anything this time, I can't get the new RAM out. I am on my wife's 4 year old iMac now. I just saw a video that showed I could have two layers of RAM on each side. I didn't notice that on mine. That implies I could use my old 2G with my 4G or with my wife's 2G.

But I've first got to remove my 4G RAM and re-set it and try again.
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Old Dec 7, 2010, 06:57 PM   #30
Ibrajim
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Join Date: Dec 2010
Quote:
Originally Posted by jsteelm View Post
Theres a flaw with either the Intel chipset or the apple EFI or both. Im guessing the EFI as the Intel chipset exists in other laptops and we have not heard anything on other laptops having this issue.

Anyway, my solution was this:

*****DISCLAIMER: I take no responsibility for voiding RAM warranty or harming the computer by using this program********

Boot into bootcamp (one 800mhz ram stick one 667mhz ram stick) and use this:
http://forums.techpowerup.com/showthread.php?t=20349

Change the CAS to 3ns from 2.5ns to make the RAM 333Mhz (with dual data rate thats 666, oh but thats evil, better round up the .1 to 667)

Make sure to use the "edit change checksum" or something of the like. Just DO NOT WRITE THE DATA WITH INVALID CHECKSUM!!! You only really need to do this with 1 RAM stick as the other one will be throttled down to match the lower speed by the chipset (oh right, it works, go figure its an EFI problem).

Anyway, enjoy this hotfix until Apple fixes their proprietary hardware interface software. If you break your RAM, tough luck, complain at Apple or accept the responsibility that you didn't know what you were doing and broke it.
Can I do that using parallels desktop instead of bootcamp?
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Old Dec 8, 2010, 09:01 AM   #31
RedTomato
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This thread is over 2 years old.

Any information in here is outdated. You're better off making a new thread.
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Old Feb 2, 2013, 07:39 AM   #32
Gablud
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Join Date: Feb 2013
CanadaRAM! Thanks greatly that you wrote about sore thumbs and symptoms as black screen an flashing light when "Pro black screen after RAM change" That comment saved me a visit to the workshop and a regretful customer who tried to modify his old mac Pushing the RAM harder in place, I did, and its now working perfect! The sun has returned to me and this little Swedish town where I live. My kids happy too! Again many many thanks to you from my heart!!!! Now my kids back on minecraft and its coffee time for myself *sigh* )
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