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Test Drive: Apple Mac Pro Memory

Jul 13, 2009 12:00 PM, By Jan Ozer

How Much Memory is enough?

Apple sent the original Mac Pro to me with 12GB of RAM (six-2GB), and I was interested to see how upping that configuration to 24GB of RAM (six-4GB) would impact performance. To make a long story short, not much. To add some perspective, I threw in performance stats at 8GB using a four-2GB configuration. That means two 2GB DIMMs in each side of the Mac Pro’s memory tray, with slots 3 and 4 open on both sides.

Apple sells the dual-CPU Mac Pro in the two-2GB-per-processor, 8GB total configuration, with the upgrade to 12GB (six-2GB) only $200 more. Apple doesn’t offer the 24GB configuration, but the 32GB configuration costs $6,100 extra, which I extrapolated down to $4,000 for Table 1 as a rough guess of the price for a 24GB configuration. I know you can buy cheaper memory from other outlets, including Crucial and Trans International, but configurations are priced differently and always changing, so let’s use the Apple numbers for comparison.

Final Cut Pro

I ran multiple tests using multiple programs. Let’s start with Final Cut Pro, which involved a 30-minute wedding ceremony shot and edited by Carrie Cannaday, a shooter/editor of broadcast, wedding, and other event work in southwest Virginia. Cannaday shot in HDV with multiple camcorders, which I rendered to a QuickTime Reference Movie. I then input that file into Apple Compressor and produced an H.264 file for streaming and a DVD-compatible MPEG-2 file. The comparative times are shown in Table 1.

Note that the percentage differences in the 12GB column measure the difference between 8GB and 12GB configuration, while the percentage differences in the 24GB column measure the difference between 12GB and 24GB. Any way you look at it, the performance differences are fairly minor throughout and not always in favor of the higher memory configurations (and yes, where anomalies existed, I tested twice to confirm).

For example, the 12GB configuration was actually slower at H.264 encoding than the 8GB, though not by much. The lack of substantial difference is even more surprising given that the 12GB configuration was theoretically optimal (one DIMM per memory controller channel) while the 8GB wasn’t (one channel open). Still, for $200 extra, the 12GB appears to be worth the price, while the 24GB configuration clearly isn’t for these applications.

Adobe CS4: Real World

The second round of tests involved Adobe Media Encoder and two of my own real-world projects. The first was a 90-minute ballet shot with two HDV camcorders mixed via Adobe Premiere Pro’s multicam feature and rendered to MPEG-2 for an SD DVD. The second and third tests involved a 10-minute single-camera DV shoot produced as an audition for America’s Got Talent. I rendered that file to H.264 and to MPEG-2.

Again, some anomalies, though in the longest and most demanding test, the 12GB configuration was 10 percent faster than the 8GB configuration for only $200. I’d spend the money. I didn’t see any results that even tempted me to go higher than 12GB.

Adobe CS4: Synthetic

I produce mostly in HDV with a smattering of AVCHD, though this latter component is increasing. Beyond my personal choices, I wondered how additional memory impacts working with different HD formats?

To test this, I used a series of multiformat synthetic benchmark tests, one a short project of 2 minutes or less, the other 10 minutes long. The short project involved multiple picture-in-picture effects, including an Adobe After Effects chroma key effect incorporated via Dynamic Link. My goal was to stress system memory and simulate the production of a heavily edited but short project such as a 60-second commercial.

The second round of tests involves 10 minutes of lightly edited source material, including color correction and a logo, but no picture-in-picture or Dynamic Link. This test was designed to assess pure throughput in the typical event-type production such as concerts, ballets, and sporting events. Note that I didn’t run the long test on the Red Digital Cinema footage in all configurations because of time considerations and the fact that if you shoot with a Red camera, you can probably find the extra $200 for the 12GB of RAM. For the record, I rendered all formats to the outputs specified in Table 3.

Again, while the results aren’t striking, I’d spend the $200 extra for the 12GB, and probably wouldn’t opt for the 24GB configuration unless I was working on extremely time-sensitive materials.

Telestream Episode Engine

The final tests involved Telestream Episode Engine, a streaming-media encoder with very efficient multiprocessor use. Here I ran two tests. The first involved encoding a single HD file to nine different streaming formats: a mix of VP6, H.264, and Windows Media output in different resolutions and data rates. The second involved encoding 16 1-minute SD source files to 14 output files in the same three streaming formats, plus MPEG-2.

Again, the time savings associated with the additional RAM wasn’t striking. I checked these results with the Telestream folks, who said that they recommend 1GB of RAM per CPU, and weren’t surprised that the additional RAM beyond 8GB produced negligible benefits. Hey, efficient code is efficient code. Still, if you’re configuring a Mac Pro for heavy-duty batch encoding use with Episode Engine, I’d spend the dough for 12GB, but no more.

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