What is the performance difference of the Mac mini "Core" using matched or unmatched RAM?

For those who are not already aware, as noted elsewhere in the Mac mini "Core" Q&A, Apple states that "for optimum performance, it is recommended to use two SO-DIMMs (one in each slot) of the same DIMM size (e.g. two 512 MB SO-DIMMs)" with the Intel-based Mac mini systems.

As all of the Mac mini "Core" models are configured by default with dual 256 MB SO-DIMMs, it seems likely that the majority of users who upgrade simply will follow Apple's recommendation and install dual 512 MB or 1.0 GB SO-DIMM RAM modules.

However, there have been several readers curious about the performance difference when using matched or unmatched RAM.

BareFeats posted a great "shootout" comparing the performance of a Mac mini "Core Duo" 1.66 with a matched pair of 1 GB RAM SO-DIMM modules to a Mac mini "Core Duo" 1.66 with an unmatched pair of RAM (with a 256 MB and 1 GB module), as well as a Mac mini G4/1.42 and iMac "Core Duo" 1.83 17".

BareFeats has done a great job as always, and the article should be read in its entirety. Nevertheless, for example, regarding the "real-world" performance difference between the matched and unmatched systems, BareFeats reports that it took 47 seconds to "Render Soft Focus" in iMovie HD with the matched system and 48 seconds with the unmatched system.

In a "BOF Botmatch (10x7)" test in Unreal Tournament 2004, BareFeats reports both systems coughed up a dismal seven FPS (frames per second). In a "1024x768 Medium" test of Doom 3, the matched system eked out thirteen FPS and the unmatched system eleven. Finally, in a "1024x768 Maximum" test of Quake 3, the matched system churned out 86 FPS, whereas the unmatched system 57 FPS, a whopping 29 FPS difference.

As one would expect given those results, the author concludes in a "performance summary" that:

The Intel [Mac] mini ["Core Duo" 1.66] seemed only slightly affected by unmatched memory pairs until we ran Quake 3. In that test, matching memory was 51% faster. We recommend matching memory of either two 512 MB modules or two 1 GB modules. Just booting up the mini and doing nothing else consumes 270 MB, so [the pre-installed] two 256 MB modules just doesn't cut it.

Essentially, the performance difference between using matched or unmatched memory is most notable when performing graphics-intensive tasks. This is to be expected given the video subsystem's reliance on the system RAM. If access to the system RAM is faster, video-related tasks will be faster as well.

Site sponsor Other World Computing soon will release tests comparing the speed of the Mac mini "Core 2 Duo" models using matched and mismatched memory. When these tests are available, this Q&A will be updated.