Upgrading my early-2009 iMac with Open Core Legacy Patcher

[CLOD-HOPPER]

Hello, experts. I'm not sure that this is the correct forum in which to ask my question (since I am asking a question about doing something with a machine that has not been in use for some years, and which has El Capitan installed on it). The machine on which this message is being typed is a different one, and is slightly more up-to-date (it runs High Sierra). The other machine cannot go beyond El Capitan.

Essentially, my question is about using Open Core Legacy Patcher on the first-mentioned machine, so as to be able to install Big Sur or later on it. I must make it very clear that technical understanding is something that I do not possess, so for me, going into Legacy Patcher matters is akin to a six-year-old having to walk into a jungle — it scares me to death. Yet, if my early-2009, 24-inch iMac could be made to run with a slightly more modern OS, it would solve a huge problem.

What I need to know is which version of Open Core Legacy patcher to use for the above task? The latest version (1.4.3) seems to be ok, but when I scroll down the earlier versions, version 1.0.0 seems OK too (it mentions 2009 iMacs, whereas version 1.4.3 does not), and I don't know which I ought to use.

Will some kind (and tech-savvy soul) tell me which version to download and use?
With thanks in hopeful anticipation,
C.H.

 

[sdfox7]

Each version of OpenCore introduces compatibility and functionality fixes. I wouldn't recommend using an older version than the current one.

That said, I wouldn't recommend going past Monterey on a machine that old. The Early 2009 iMac maxes out at 8GB RAM and Ventura and Sonoma use more resources than Monterey. If you stuck an SSD and 8GB RAM into that machine it should run pretty well.

No modern OS is going to run well on spinning rust HDD, so I'd highly recommend the SSD.

Download and build macOS Installers​

 

[CLOD-HOPPER]

Each version of OpenCore introduces compatibility and functionality fixes. I wouldn't recommend using an older version than the current one.

That said, I wouldn't recommend going past Monterey on a machine that old. The Early 2009 iMac maxes out at 8GB RAM and Ventura and Sonoma use more resources than Monterey. If you stuck an SSD and 8GB RAM into that machine it should run pretty well.

No modern OS is going to run well on spinning rust HDD, so I'd highly recommend the SSD.

Download and build macOS Installers​

sdfox7, you have provided information that has been useful already! I intended to install Big Sur, but you seem to think that Monterey would be OK, so I shall download that, instead. Yes, I had intended to upgrade the Ram to 8GB (it has four, I think, as it is). Also (all being well), I shall have an SSD drive installed as you recommend. I am very appreciative of your comments, and I thank you very much indeed.

This may be pushing my luck (perhaps it really ought to be a new thread), but I shall ask, just in case you would be willing to help further. When it was bought new from Apple, this 2009 iMac had a fault that Apple knew about (a "known issue"), but I did not know about it, and I failed to take advantage of Apple's policy of putting it right at no cost to the user. The fault was that, around the edges of the screen, there was a creeping blackness, which, with time, encroached ever more. Of course, when I started to use the iMac, there was no black edge to the screen — it appeared over months of use. However, from the Web, I found out, not how to cure it permanently, but to clean this blackness (temporarily).

Now, when I have the SSD and the extra RAM installed (at a Mac-repair shop), I should like to have this screen problem addressed, also. The difficulty is that I feel fairly sure that what would be offered would not be a repair of this screen but a replacement (with a used one, inevitably, considering the age of the machine). I am not at all keen on that prospect, because my mid-2010 iMac (the one on which I am typing, now) had a failed screen replaced (with a used one), about two years ago, and the guarantee was only for about three or four months. In such a case, to have memory upgraded on the 2009 machine, and a SSD installed, would be an expensive gamble, because a previously-used screen might fail in a few months, and all those expensive upgrades lost.

So, with all that background, my question is this: would it be realistic to ask the shop to repair the self-same screen? I mean, it may only need some simple component to be replaced, to make it almost like new (that old iMac has only seen about 18 months use).

The reason why I am asking you this question, sdfox7 (instead of asking the owner of the Mac-repair shop), is that I find it very difficult to converse with him on the telephone (he has a very heavy foreign accent), and I am not physically mobile enough to go to the shop, which is several miles away.

Please do your best to answer my question, if you can. Thanks again!
C.H.

 

[sdfox7]

sdfox7, you have provided information that has been useful already! I intended to install Big Sur, but you seem to think that Monterey would be OK, so I shall download that, instead. Yes, I had intended to upgrade the Ram to 8GB (it has four, I think, as it is). Also (all being well), I shall have an SSD drive installed as you recommend. I am very appreciative of your comments, and I thank you very much indeed.

This may be pushing my luck (perhaps it really ought to be a new thread), but I shall ask, just in case you would be willing to help further. When it was bought new from Apple, this 2009 iMac had a fault that Apple knew about (a "known issue"), but I did not know about it, and I failed to take advantage of Apple's policy of putting it right at no cost to the user. The fault was that, around the edges of the screen, there was a creeping blackness, which, with time, encroached ever more. Of course, when I started to use the iMac, there was no black edge to the screen — it appeared over months of use. However, from the Web, I found out, not how to cure it permanently, but to clean this blackness (temporarily).

Now, when I have the SSD and the extra RAM installed (at a Mac-repair shop), I should like to have this screen problem addressed, also. The difficulty is that I feel fairly sure that what would be offered would not be a repair of this screen but a replacement (with a used one, inevitably, considering the age of the machine). I am not at all keen on that prospect, because my mid-2010 iMac (the one on which I am typing, now) had a failed screen replaced (with a used one), about two years ago, and the guarantee was only for about three or four months. In such a case, to have memory upgraded on the 2009 machine, and a SSD installed, would be an expensive gamble, because a previously-used screen might fail in a few months, and all those expensive upgrades lost.

So, with all that background, my question is this: would it be realistic to ask the shop to repair the self-same screen? I mean, it may only need some simple component to be replaced, to make it almost like new (that old iMac has only seen about 18 months use).

The reason why I am asking you this question, sdfox7 (instead of asking the owner of the Mac-repair shop), is that I find it very difficult to converse with him on the telephone (he has a very heavy foreign accent), and I am not physically mobile enough to go to the shop, which is several miles away.

Please do your best to answer my question, if you can. Thanks again!
C.H.

You have to weigh the cost of upgrading a machine with a known flaw vs another machine.

2009-2010 iMacs aren't that expensive in this day and age so it might be better to identify/buy another machine not affected by the flaw--this would probably offset the cost of a new screen install. Plus, could a new screen fail, AGAIN?

We are also talking about a 15 year old machine that could fail at any time for any reason.

You could find one inexpensively locally, even a late 2015 iMac from MacOfAllTrades with 8GB/256GB SSD for just $199.

https://www.macofalltrades.com/apple-imac-21-5-inch-1-6ghz-core-i5-late-2015/

 

[CLOD-HOPPER]

You have to weigh the cost of upgrading a machine with a known flaw vs another machine.

2009-2010 iMacs aren't that expensive in this day and age so it might be better to identify/buy another machine not affected by the flaw--this would probably offset the cost of a new screen install. Plus, could a new screen fail, AGAIN?

We are also talking about a 15 year old machine that could fail at any time for any reason.

You could find one inexpensively locally, even a late 2015 iMac from MacOfAllTrades with 8GB/256GB SSD for just $199.

https://www.macofalltrades.com/apple-imac-21-5-inch-1-6ghz-core-i5-late-2015/

sdfox7: What you said in your last reply makes sense. Previously, I should never have considered buying a used machine, but economics rules, doesn't it? The uncertain life of a pre-owned machine balances, at the very least, with the expenses that would be involved in boosting my old machine (even if it has had only a couple of years' actual use).

I shall need, then, to look at what may be on offer on the British market, and with luck, may find something entirely suitable for updating with Open Core.

Believe me, you have been most helpful in all that you have posted, and it's all greatly appreciated! Thanks, once again.
C.H.

 

[CLOD-HOPPER]

sdfox7: What you said in your last reply makes sense. Previously, I should never have considered buying a used machine, but economics rules, doesn't it? The uncertain life of a pre-owned machine balances, at the very least, with the expenses that would be involved in boosting my old machine (even if it has had only a couple of years' actual use).

I shall need, then, to look at what may be on offer on the British market, and with luck, may find something entirely suitable for updating with Open Core.

Believe me, you have been most helpful in all that you have posted, and it's all greatly appreciated! Thanks, once again.
C.H.

sdfox7, I am back again with questions about Open Core Legacy Patcher (use of). If you feel that you are being hounded, don't bother to reply. However, I should be most appreciative of any replies you might offer.

I looked for a relatively inexpensive machine on the British market, but could not find one (they seem to be much more expensive in the UK, than they are in the USA). So, I feel forced, after all, to update my late 2009 iMac, and hope for the best. However, before spending money on an SSD and extra RAM, I thought it would be wise to find out whether I am able to use OCLP successfully. With it, I downloaded Monterey and I made a USB installer. I am under the impression that OCLP does not have any part in creating this installer, and that it is just an ordinary installer, such as one would use to install native operating systems (as I have done many times in the past). Is that correct?

Well, having made the installer (on the 2009 iMac), I then clicked on the button in OCLP 1.4.3 that says: BUILD AND INSTALL OPEN CORE. In the settings, I chose 9,1, which seems to be the setting for this 2009 iMac. I then clicked the button to run this build, and a notice appeared, telling me the location of the build. At this point, I believed (perhaps mistakenly) that all that was needed then, was to install Monterey. However, when I was selecting a blank, Mac OSX Journaled GUID partition (there are three spare partitions) on which to install Monterey, a message appeared above every partition that I tried, saying that Monterey could not be installed on that partition. The build seems to be a failure! On the other hand, it may be a result of ignorance on my part.

Could you tell me what is being done wrongly, or not being done that ought to be done? Is it the fact of attempting to install on a spinning platter, instead of an SSD, or should the installer flash drive have first been modified via OCLP, before using Terminal to create the installer?

I should love to simply be able to install Monterey (whether it runs well or not), just to verify that I can do it correctly. If, eventually, it did install, I should then be able to think about having the SSD and extra RAM installed.

With thanks in hopeful anticipation of your further patience,
C.H.

 

[CLOD-HOPPER]

You have to weigh the cost of upgrading a machine with a known flaw vs another machine.

2009-2010 iMacs aren't that expensive in this day and age so it might be better to identify/buy another machine not affected by the flaw--this would probably offset the cost of a new screen install. Plus, could a new screen fail, AGAIN?

We are also talking about a 15 year old machine that could fail at any time for any reason.

You could find one inexpensively locally, even a late 2015 iMac from MacOfAllTrades with 8GB/256GB SSD for just $199.

https://www.macofalltrades.com/apple-imac-21-5-inch-1-6ghz-core-i5-late-2015/

It turned out that I felt compelled to upgrade my existing early-2009 24-inch iMac. In spite of the difficulties this involved for a not-very-clever Mac user, this has been done, and Monterey seems to run OK, though it is very slow. One final question remains, you experts, and it is this: I understand that Open Core Legacy Patcher injects stuff into the memory of a machine. Now, in order to get it to run at a reasonable speed, I need to get rid of the two 2GB RAM modules that are installed and which (seemingly) received the injection of data etc. from OCLP, and insert two 4-GB modules. Will this nullify all the hard work that this installation process has demanded?

With thanks in advance, for any informed comments,
C.H,

 

[Roverlen]

I have successfully upgraded my early 2009 iMAC 3.0Ghz to Sonoma 14.6.1 and the OpenCore Patcher has been updated to 2.0.2. Everything runs great with no problems. The new OpenCore autoupdates with your permission.
However, now I would like to upgrade RAM to 2x8Gb memory cards that are designated GSTD38G1600 8Gb DDR3 1600 running at 1333Mhz. unfortunately when replacing the cards I get the dreaded three beeps. I tried just one at a time and still beeps. I believe and I have read that before you alter your iMAC using OpenCore, you must do the RAM (hardware first). As a consequence I am stuck with these two new modules until I can find an answer from GitHub.
I tried this on a Mid 2010 MacBook Pro running High Sierra and no OpenCore installed as yet. Same problem until I left one original Crucial 4Gb card in and filled the second slot with the 'Gigastone 8gb 1600 card'. I was successful and the MacBook Pro runs with 4 + 8 totalling 12Gb of RAM.
Still looking for an answer on how to do the same with the early 2009 iMac with Sonoma already installed.

If you find and answer to my problem of running with Sonoma and installing the RAM without having to revert to El Capitan and then installing OpenCore again.

At least you know that upgrading is possible for the iMac using 1333Mhz card versus original 1067Mhz.

Let me know how you make out. I'm busy with Terminal commands and Homebrew looking for a solution to override boot process.

Regards, Roverlen

 

[Roverlen]

Hello, experts. I'm not sure that this is the correct forum in which to ask my question (since I am asking a question about doing something with a machine that has not been in use for some years, and which has El Capitan installed on it). The machine on which this message is being typed is a different one, and is slightly more up-to-date (it runs High Sierra). The other machine cannot go beyond El Capitan.

Essentially, my question is about using Open Core Legacy Patcher on the first-mentioned machine, so as to be able to install Big Sur or later on it. I must make it very clear that technical understanding is something that I do not possess, so for me, going into Legacy Patcher matters is akin to a six-year-old having to walk into a jungle — it scares me to death. Yet, if my early-2009, 24-inch iMac could be made to run with a slightly more modern OS, it would solve a huge problem.

What I need to know is which version of Open Core Legacy patcher to use for the above task? The latest version (1.4.3) seems to be ok, but when I scroll down the earlier versions, version 1.0.0 seems OK too (it mentions 2009 iMacs, whereas version 1.4.3 does not), and I don't know which I ought to use.

Will some kind (and tech-savvy soul) tell me which version to download and use?
With thanks in hopeful anticipation,
C.H.

I have successfully upgraded my early 2009 iMAC 3.0Ghz to Sonoma 14.6.1 and the OpenCore Patcher has been updated to 2.0.2. Everything runs great with no problems. The new OpenCore autoupdates with your permission.
However, now I would like to upgrade RAM to 2x8Gb memory cards that are designated GSTD38G1600 8Gb DDR3 1600 running at 1333Mhz. unfortunately when replacing the cards I get the dreaded three beeps. I tried just one at a time and still beeps. I believe and I have read that before you alter your iMAC using OpenCore, you must do the RAM (hardware first). As a consequence I am stuck with these two new modules until I can find an answer from GitHub.
I tried this on a Mid 2010 MacBook Pro running High Sierra and no OpenCore installed as yet. Same problem until I left one original Crucial 4Gb card in and filled the second slot with the 'Gigastone 8gb 1600 card'. I was successful and the MacBook Pro runs with 4 + 8 totalling 12Gb of RAM.
Still looking for an answer on how to do the same with the early 2009 iMac with Sonoma already installed.

If you find and answer to my problem of running with Sonoma and installing the RAM without having to revert to El Capitan and then installing OpenCore again.

At least you know that upgrading is possible for the iMac using 1333Mhz card versus original 1067Mhz.

Let me know how you make out. I'm busy with Terminal commands and Homebrew looking for a solution to override boot process.

Regards, Roverlen

 

[CLOD-HOPPER]

I have successfully upgraded my early 2009 iMAC 3.0Ghz to Sonoma 14.6.1 and the OpenCore Patcher has been updated to 2.0.2. Everything runs great with no problems. The new OpenCore autoupdates with your permission.
However, now I would like to upgrade RAM to 2x8Gb memory cards that are designated GSTD38G1600 8Gb DDR3 1600 running at 1333Mhz. unfortunately when replacing the cards I get the dreaded three beeps. I tried just one at a time and still beeps. I believe and I have read that before you alter your iMAC using OpenCore, you must do the RAM (hardware first). As a consequence I am stuck with these two new modules until I can find an answer from GitHub.
I tried this on a Mid 2010 MacBook Pro running High Sierra and no OpenCore installed as yet. Same problem until I left one original Crucial 4Gb card in and filled the second slot with the 'Gigastone 8gb 1600 card'. I was successful and the MacBook Pro runs with 4 + 8 totalling 12Gb of RAM.
Still looking for an answer on how to do the same with the early 2009 iMac with Sonoma already installed.

If you find and answer to my problem of running with Sonoma and installing the RAM without having to revert to El Capitan and then installing OpenCore again.

At least you know that upgrading is possible for the iMac using 1333Mhz card versus original 1067Mhz.

Let me know how you make out. I'm busy with Terminal commands and Homebrew looking for a solution to override boot process.

Regards, Roverlen

Roverlen, seeing that no one has responded, I should like to offer my two-pennyworth (it might not even be worth that, but to me, it seems logical). As you may know from this thread, I have installed, against all the perceive odds, Monterey on a 2009 iMac, and it works fine. You say you have a problem with the memory modules, which ought to have been upgraded before installing. As I understand things, O.C.L.P. installs something into the memory, rather than the main drive. If your problem were my problem, I would see a need to wipe that drive (and any other associated partition (look in Disk Utility for extra stuff) clean, and re-install Sonoma onto an empty drive (or partition), after changing/updating the memory modules (while the machine is switched off, of course). If, in suggesting this, I am showing how green I am, please accept my apologies. However, I hope this will help.
C.H.

 

[Roverlen]

Clod-Hopper:

Thank you for the reply. If I understand you correctly, you're suggesting loading Sonoma back onto a clean SSD or partition AFTER upgrading the RAM.
I assume that this is supposed to detect the newer RAM on install. Hopefully this is true.
In the mean time I will spend a few days looking for a remedial way of accepting the new RAM by Terminal commands or some Algorithm from 'Homebrew'.
As for your suggestion which sounds plausible, I was under the impression that El Capitan would have to be installed to recognize the RAM. I may be wrong in this theory.
The other possibility is to clear the NVRAM from memory but I'm not sure of the consequences of doing that. The iMac is working great with all updates and I would hate to mess that up.
Regards, Roverlen

 

[CLOD-HOPPER]

Clod-Hopper:

Thank you for the reply. If I understand you correctly, you're suggesting loading Sonoma back onto a clean SSD or partition AFTER upgrading the RAM.
I assume that this is supposed to detect the newer RAM on install. Hopefully this is true.
In the mean time I will spend a few days looking for a remedial way of accepting the new RAM by Terminal commands or some Algorithm from 'Homebrew'.
As for your suggestion which sounds plausible, I was under the impression that El Capitan would have to be installed to recognize the RAM. I may be wrong in this theory.
The other possibility is to clear the NVRAM from memory but I'm not sure of the consequences of doing that. The iMac is working great with all updates and I would hate to mess that up.
Regards, Roverlen

Roverlen, I am not very tech-savvy, but the only reason that there is a need for any other MacOS to be installed is that there needs to be somewhere to lodge the OCLP app, ready for use. (I am assuming that an installer for Sonama has already been made and is on a flash drive, ready to boot up with.) Could you not split the drive you are wanting to install Sonoma onto, into two partitions? On one, you could install an old, compatible OS, with the OCLP app stored ready on it, and install Sonoma onto the other partition.
I don't recall reading any remark from you about the drive you are wanting to install Sonoma onto. I suppose that, at a pinch, it could be installed on a spinning platter HD, but it would be much, much more at home on a SSD. Whatever you, I wish you the best of luck.
C.H.

 

[Roverlen]

Roverlen, I am not very tech-savvy, but the only reason that there is a need for any other MacOS to be installed is that there needs to be somewhere to lodge the OCLP app, ready for use. (I am assuming that an installer for Sonama has already been made and is on a flash drive, ready to boot up with.) Could you not split the drive you are wanting to install Sonoma onto, into two partitions? On one, you could install an old, compatible OS, with the OCLP app stored ready on it, and install Sonoma onto the other partition.
I don't recall reading any remark from you about the drive you are wanting to install Sonoma onto. I suppose that, at a pinch, it could be installed on a spinning platter HD, but it would be much, much more at home on a SSD. Whatever you, I wish you the best of luck.
C.H.

Clod-Hopper;

Thanks for the response. I already have a SSD installed about 2 years ago using OCLP for Monterey. Updates as I indicated before are always available and it requires your permission to install. My USB drive for installing was Monterey so not very useful based on Sonoma. It was unfortunate that I didn't read about the RAM business prior to updating the OSX.
It appears now that I may have to revert back to El Capitan then install. I would rather like trying the clearing of the MVRAM first to see is that helps. I just need someone to indicate if this helps and allows me to install the new RAM and then reboot. If no one has a response , I'll just give it a try and hope that my assumption is correct.

Thanks for taking the time to respond with possibilities.


Roverlen

(If you know anything of LandRovers, then you'll know I'm a sucker for technical things).

 

[DeltaMac]

You really don't need an older boot system to have some random newer MacOS system with OCLP on the same Mac.
One reason to install that older system(maybe the newest system that will run on your Mac natively), would be for a reinstall to make sure that your Mac has the latest firmware update (which would be upgraded automatically as part of a system install. You would not need to keep that older version, unless you would need to boot into that older system, maybe because you need to run some older software that won't run on the primary system where you need the OCLP support. But, sometimes you just want to have an older system, just so you have it, if needed. I have a 2008 iMac (iMac 8,1) which has 3 boot systems, each on its own partition: Leopard 10.5.8 (Oldest supported system); El Capitan 10.11.6 (newest supported system), and now Sequoia 15.1 (OCLP), all running with the most RAM it will support, which is 6GB. There's no way to make it recognize more than that - it is a hardware limitation of the CPU and the chipset used, and is not a software limitation in any way. (Sequoia doesn't like that small amount of RAM, and it's an experimental setup for me (mostly just for fun), and I dont use it for any kind of production use, just for fun. Not a big deal as long as I keep my expectations low

 

[Roverlen]

You really don't need an older boot system to have some random newer MacOS system with OCLP on the same Mac.
One reason to install that older system(maybe the newest system that will run on your Mac natively), would be for a reinstall to make sure that your Mac has the latest firmware update (which would be upgraded automatically as part of a system install. You would not need to keep that older version, unless you would need to boot into that older system, maybe because you need to run some older software that won't run on the primary system where you need the OCLP support. But, sometimes you just want to have an older system, just so you have it, if needed. I have a 2008 iMac (iMac 8,1) which has 3 boot systems, each on its own partition: Leopard 10.5.8 (Oldest supported system); El Capitan 10.11.6 (newest supported system), and now Sequoia 15.1 (OCLP), all running with the most RAM it will support, which is 6GB. There's no way to make it recognize more than that - it is a hardware limitation of the CPU and the chipset used, and is not a software limitation in any way. (Sequoia doesn't like that small amount of RAM, and it's an experimental setup for me (mostly just for fun), and I dont use it for any kind of production use, just for fun. Not a big deal as long as I keep my expectations low

DeltaMac:

I don't have an older system or boot on the SSD as I assume. Certainly not interested in old software that won't run on APFS format. In fact any App that was antiquated was greyed out and simply not available under the latest OSX Sonoma.
The Computer is strictly for average use and not work related. Mail, Word Document, etc.
The specifications of this iMac is a maximum of 8Gb in two slots. I was under the impression if prior to OCLP and updated the RAM to 16Gb as suggested by others on GitHub, this would prevent paging or Swap Drive usage. This anomaly adds up write called TBW on SSD and shortens its life and for this reason I wanted to increase RAM to prevent this occurrence.
What I'm looking for is some way of having the OSX or NVRAM recognizing the new modules without three beeps.
That is the reason I am looking for some way around installing El Capitan to allow RAM module to be recognized. That is by Terminal command possibly clearing NVRAM. Not sure if that is the way to. I was under the impression that now Sonoma is installed the boot system is newer as well but not recognizing the RAM cards. Correct me if I'm wrong.
Roverlen

 

[DeltaMac]

Unfortunately, you can't assume that upgrading one Mac (your 2010 MacBookPro) to 16 GB, somehow enables a completely different Mac (your early 2009 iMac) to also be capable of that upgrade to 16GB. This is absolutely not a software issue, but is simply how the hardware recognizes, and uses, RAM. If you want to do a reset when upgrading your RAM: double check that the RAM that you want to use is compatible with your Mac. Your Early 2009 iMac accepts PC3-8500 (1066 MHz) DDR3 SO-DIMM. Maximum in each of the two slots is 4GB. That capacity, again, is not related to the software that you boot to, but is a hardware limitation. (You can't go to 8GB sticks, limit is 4GB x 2. The ONLY way to go to more is to replace with a newer iMac. Late 2009 is a different generation, the Late 2009 iMac 27-inch can go to 32 GB (8GB in each of 4 slots), but the Early 2008 should not be expected to work with 8GBx2. 4GB x 2 is final.
Finally, the 3 beeps when you try 8GB sticks means that the memory is, maybe, passing POST (so accepted by the hardware) but the software is refusing to boot from that RAM for some reason. If you are sure it is correct specification RAM, try reseating the same RAM, and try to boot again. If you still get the 3 beeps, try only one RAM stick, in one slot, then try again in the other slot. Try that RAM in a different Mac that you know should work with that RAM.
Finally, try a different set of the RAM that you know is compatible with your Mac.
Try the NVRAM reset, known as a PRAM reset on older Macs, but is the same function: Shut your iMac off, then restart, while holding Option-Command-P-R. You should hear a boot chime sound. Keep holding the same 4 keys until you hear the boot chime 2 more times, then release the keys. The NVRAM reset will un-set the choice for boot drive, so you will hold the Option key to get the boot picker screen. Choose your boot drive on that screen. Go in to the settings, then the Startup Disk pane, to select the boot disk that you will use as the default for your system.

One more thing... You have a 15 year old Mac. Boot issues can sometimes be caused by a low, or dead battery, and occasionally will cause very strange issues. It's probably a good idea to replace a possibly-original battery. That battery can easily be replaced after removing the front bezel. It's a button battery, specifically a BR-2032. Replacing THAT will also force a full hardware reset when you next boot.
I actually would love to be proven wrong about the 8GB RAM sticks, but some Macs simply don't accept the possibility.

 

[Roverlen]

Unfortunately, you can't assume that upgrading one Mac (your 2010 MacBookPro) to 16 GB, somehow enables a completely different Mac (your early 2009 iMac) to also be capable of that upgrade to 16GB. This is absolutely not a software issue, but is simply how the hardware recognizes, and uses, RAM. If you want to do a reset when upgrading your RAM: double check that the RAM that you want to use is compatible with your Mac. Your Early 2009 iMac accepts PC3-8500 (1066 MHz) DDR3 SO-DIMM. Maximum in each of the two slots is 4GB. That capacity, again, is not related to the software that you boot to, but is a hardware limitation. (You can't go to 8GB sticks, limit is 4GB x 2. The ONLY way to go to more is to replace with a newer iMac. Late 2009 is a different generation, the Late 2009 iMac 27-inch can go to 32 GB (8GB in each of 4 slots), but the Early 2008 should not be expected to work with 8GBx2. 4GB x 2 is final.
Finally, the 3 beeps when you try 8GB sticks means that the memory is, maybe, passing POST (so accepted by the hardware) but the software is refusing to boot from that RAM for some reason. If you are sure it is correct specification RAM, try reseating the same RAM, and try to boot again. If you still get the 3 beeps, try only one RAM stick, in one slot, then try again in the other slot. Try that RAM in a different Mac that you know should work with that RAM.
Finally, try a different set of the RAM that you know is compatible with your Mac.
Try the NVRAM reset, known as a PRAM reset on older Macs, but is the same function: Shut your iMac off, then restart, while holding Option-Command-P-R. You should hear a boot chime sound. Keep holding the same 4 keys until you hear the boot chime 2 more times, then release the keys. The NVRAM reset will un-set the choice for boot drive, so you will hold the Option key to get the boot picker screen. Choose your boot drive on that screen. Go in to the settings, then the Startup Disk pane, to select the boot disk that you will use as the default for your system.

One more thing... You have a 15 year old Mac. Boot issues can sometimes be caused by a low, or dead battery, and occasionally will cause very strange issues. It's probably a good idea to replace a possibly-original battery. That battery can easily be replaced after removing the front bezel. It's a button battery, specifically a BR-2032. Replacing THAT will also force a full hardware reset when you next boot.
I actually would love to be proven wrong about the 8GB RAM sticks, but some Macs simply don't accept the possibility.

DeltaMac:

Thanks for the advice. I'll give your suggestions a try.
You are correct about my specifications for the early 2009 24" iMac. I was aware that it was DDR3 1066Mhz but an article on the Internet said that the Ram could be upgraded to 16 Gb by using DDR3 1600 (1333Mhz) 8 Gb cards of 204 PIN. This is what I purchased and used on the mid 2010 MacBook Pro and it worked with the Original 4 Gb card plus the new 8Gb card of the same specifications.
Since that worked there , I assumed the iMac would behave the same. Hence, the three beeps. I tried similar arrangement like the MacBook Pro and no luck. The only thing I didn't try was just using the new 8Gb card by itself. You may be correct in that the hardware is the refusal point and not software.
So I will try your suggestions as indicated in the last half of the reply.
Keep your fingers crossed, hopefully the article on the Web is correct and you can exceed Apple's memory maximum as long as you keep the same DDR3 specs and 1333Mhz.
As for the button battery, I don't recall seeing on inside. I have had this unit apart a few times upgrading and if it was evident I would have replaced it. I'll check the Apples specs one more time.
I take it that there is no Terminal or Linux command to alter sys profiler settings to accomplish the same thing.
Roverlen


Roverlen

 

[DeltaMac]

Your battery is in the location highlighted in this screenshot...

Again, it is a BR2032

 

[Roverlen]

Your battery is in the location highlighted in this screenshot... View attachment 2441955
Again, it is a BR2032

Well, no success on alternating installation of RAM cards as suggested, Next step button cell.