Upgrading the CPU and Hard Drive of an iMac Aluminum (part 1)


Being an early adopter is good because well, you get to play first. Unfortunately, it also means that your hardware will be obsolete much earlier. Never mind paying premium. Thing is, eventually you will need better hardware and upgrading should keep you up to speed for some time.

Upgrading most non Apple hardware poses no problem as its very easy to just swap parts to keep up with software demands. For apple product though it can be a problem. Historically, apple products have been very difficult to upgrade except for some peripherals as hdd and memory.

This post will show you that “some” apple products will enable you to take upgrading much further. Mind that not all Intel macs are upgradable. Some of them will have BGA processors and are not suited for an upgrade. You can find out if yous has a Micro-FCPGA socket here.

We will be upgrading the CPU and Hard Drive of a mid 2007 iMac Aluminum.

The Rig

The iMac “Core 2 Duo” 2.0 20-Inch (Aluminum) features a 2.0 GHz Intel “Core 2 Duo” processor (T7300), with two independent processor “cores” on a single silicon chip, a 4 MB shared level 2 cache, an 800 MHz system bus, 4 GB of RAM (800 MHz DDR2 SDRAM), a 250 GB (7200 RPM) Serial ATA hard drive, a vertically-mounted slot-loading DVD+R DL “SuperDrive”, ATI Radeon HD 2400 XT graphics acceleration with 128 MB of GDDR3 memory, a built-in iSight video camera, and built-in stereo speakers underneath the 20″ glossy TFT Active Matrix LCD (1680×1050 native)

Choosing the right replacement parts.

– Hard Drive

There is no secret in choosing a replacement HDD. Any SATA model and it will work just fine. This site will help you choose a good one.

The iMac shipped with a Seagate ST3250820ASQ. It is a 7200 rpm drive with 8MB cache and it scores 323 points on Passmark test.
The replacement is a Maxtor STM3750330AS. It is a 7200 rpm drive with 32Mb of cache and it scores 590.

Benchmarks are based on sequential read/write and random read/write. And as stated, no secrets here, just get the biggest, fastest drive you can afford.


The CPU has to be chosen carefully. There are constraints you have to take in account for choosing a correct replacement. Relevant parameters for choosing a replacement CPU are FSB speed, thermal design power and voltage range.

The FSB speed will ensure the replacement CPU will met specifications of the motherboard. Mind that on a mac you just cannot choose any FSB because there is no tweaking, no jumpers and no bios (its actually an EFI, but you wont be able to mess with it). Mine had 800mhz FSB so the processor would have to have the same FSB. If you choose a higher FSB processor, it will be underclocked. And because intel core 2 duo (except Extreme) has locked multipliers, the CPU speed will be underclocked too. So stick to your current FSB.

Thermal design is important too because there is no room for cooler/heatsink hacking. Your new processor will have to use the existing cooling solution. With that in mind you have to make sure your new processor dissipates the same amount of heat as the previews one.

Voltage range is critical. You cannot choose a processor that draws more energy than the previews one, period. Either it will not run smoothly under high loads, lock up or fry your motherboard. Stick to a processor that has close voltage requirements as the previews one.

With all that in mind I’ve chosen to replace the Intel T7300 (SLA45) that shipped with the iMac for a T9500 (SLAQH).

The T9500 is a 2.6Ghz, 6Mb cache and has the same 35W thermal design power. I also requires voltages within the boundaries of the SLA45 and should be a very safe replacement.

Head to Intel processor finder to choose choose your processor.

Part 2 is now avaliable, check it out!