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John T. F.
John T. F., Mac Druid
Category: Mac
Satisfied Customers: 2942
Experience:  20+ years in the computer/Mac industry
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What can I do to make my old iMac run faster?

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What can I do to make my old iMac run faster?
Hello! My name isXXXXX will work diligently to provide accurate advice and information.

Can you tell me what version of OS X you are currently running?

Click the Apple Logo in the menubar at the top of the screen

Select "About This Mac"

In the window that opens, look for the "Version" information. Please let me know what it says.

Then, repeatedly click on the word "Version" until it says "Serial Number" and please provide that number, as well.

Customer: replied 2 years ago.

Version 10.5.8


Thanks, Tom.

I show that this is a PowerPC based iMac from 2003 and was a custom order in some way. On that same screen, can you tell me the amount of memory and processor it lists?

Customer: replied 2 years ago.

Memory - 1 GB

1 CPU - 1.25 GHz

Thanks again.

Due to the age and processor in the iMac, you are actually running the latest version of software for this unit.

Beyond that your options are limited but the biggest difference in performance could be gained by upgrading the memory. Officially this unit only supports 1GB, which you already have but in reality it supports 2GB. The memory installation in this unit is slightly odd, however. There is one user serviceable slot and one that is normally only accessible by professionals.

Given you currently have 1GB, you likely have 512MB in each slot. You can verify this by clicking "more info" on the About This mac screen and looking under "Memory".

Replacing the user-accessible 512MB with a 1GB module should give you marked improvement in how applications run, particularly when more than one are running at once.

The memory for this model is rather inexpensive and can be had for around $30 from reputable sellers. I would recommend Other World Computing. They are my "go to" place for misc upgrade parts when it comes to Apple computers.

Installation is fairly easy as there is a removable plate on the very bottom of the iMac that, once removed, provides immediate access to the memory slot in the system.

If you still have concerns, please do not negatively rate my answer, simply reply back before rating. I'll be more than happy to work with you further. Hopefully, this info will answer your question. When you are satisfied, please give my answers a positive rating. You are judging my personal service only (not this website or your issue) and high ratings assure I remain in good standing.

Thanks and good luck,

John T. F. and other Mac Specialists are ready to help you
Customer: replied 2 years ago.

Thanks for the advice. But don't I need to replace the factory-installed RAM to match, otherwise it does not work?


In this case, no. The Factory installed memory is on the other side of the motherboard and not only is it difficult to access but it doesn't use the same kind of memory (It uses SDRAM technology). You *do* have to replace it if you want to reach the full maximum of 2GB but otherwise the user-installable RAM is an easy-to-access SO-DIMM that can be upgraded independently.

Customer: replied 2 years ago.

So, since I can only replace the 512 MB user-installable card, and I'll end up with 512 MB in one slot and 1 GB in the other, what is the effective memory capacity after installation?

You would go from 1GB to 1.5GB of memory, so you wind up with an extra 512MB than you had previously.

John T. F. and other Mac Specialists are ready to help you
Customer: replied 2 years ago.

If I wanted the full 2GB upgrade, I could replace the SDRAM on the motherboard (I have worked inside computers before and have a pretty good idea what I am doing - including making sure I am properly grounded to avoid ESD effects), but I suppose that replacing the SO-DIMM would be a good start just to see what effect it has. Maybe it would be enough of a boost to avoid opening up the computer.

It should make a measurable difference depending on how many apps you run at any one time.

However, if you are comfortable working inside of computers then it's not a terrible job to replace the "internal" SDRAM, too.

There is a service manual available that provides more info on gaining access:

Customer: replied 2 years ago.

Thanks! This is a very useful manual. Where should I get the thermal paste? I assume it will need to be replaced.

I have used "Arctic Silver" brand in the past. I don't see it on the OWC website but Amazon has it listed:

It's fairly decent as it doesn't run, etc, as it gets hot.

Customer: replied 2 years ago.

Is replacing the paste necessary if the existing paste appears to be in good condition?
Also, the manual you pointed me to is for the 15-inch and 17-inch iMacs. I have the 20-inch G4-1.25 GHz iMac. Is it still applicable?

You won't necessarily have to replace it, though the iMac is rather old at this point, so if it still looks good then it should be fine. If it's dried out then it should be replaced, however.

I couldn't readily provide a link for the 20" model but it should be fairly close. There may be an extra screw, etc... but any differences will be quite obvious.

John T. F. and other Mac Specialists are ready to help you
Howdy, Tom!

I'm just following up with you to see how everything is going. If you need further assistance on this issue, please let me know.

Also, feel free to request me again at any time when you come back to ask another Apple-related question.

I can be reached directly via the following page: