It's also worth noting that the smaller drives were wildly erratic in their write times. Occasionally they would spike to the speeds found in the larger capacity drives, and other times they dropped way below the average. On the other hand, the larger capacity drives were highly consistent in their read and write speeds throughout our testing.
4. Keeping lots of free space on your startup drive will improve your Mac's performance.'
Our tests on a late 2012 27-inch iMac with 2.9GHz quad-core Core i5 processor, 8GB of RAM and a 7200-rpm 1TB hard drive showed some serious performance degradation as the drive filled up. The two tests that showed the biggest change in performance were in our 6GB files and folders copy test and unzipping a 6GB compressed file. Our baseline tests, with the disk about 5 percent full, showed the iMac taking 93 seconds in the copy test and 84 seconds in the unzip test. When we filled the drive to 50 percent of its capacity, the results slowed down by 4.3 percent on the copy test and just under 8 percent on the unzip test. Filling the drive to 80 percent capacity, the baseline results were more than 11 percent faster than the almost-full iMac in the copy test and 17.6 percent faster in the unzip test. Pushing it even further, we ran the tests again at 97 percent of capacity. This time the baseline results were nearly 21 percent faster in the copy test and almost 35 percent faster on the unzip test.
With SSDs, it was a different story. Only at the 97 percent full capacity did we see any difference in our SSD results. The baseline result for SSD in the MacBook Pro was 35 percent faster, but only in the unzip test.
5. Adding RAM always improves performance.'
The lab has done quite a bit of testing on this subject over the years; our most recent coverage was last May with Mountain Lion and older versions of apps. This time out, we took a mid 2012 15-inch MacBook Pro with quad-core 2.3GHz Core i7 processor and a 512GB hard drive and ran it with 4, 8, and 16GB of RAM on loan from Crucial.
The tasks in our Photoshop tests showed the greatest benefit of increased RAM. Using our standard Speedmark 9 action script with a 100MB test file, the 8GB setup was about 14 percent faster than the 4GB configuration. Upping the RAM to 16GB shaved another couple of seconds off of the time and was 15.5 percent faster than the 4GB baseline configuration. We ran a more intensive test, one that uses more hardware acelerated tasks, and found an even greater benefit using increased RAM. In this test, the 4GB configuration took almost exactly 10 minutes to complete, upgrading the RAM to 8GB brought down the time to 7 minutes 18 seconds, and the 16GB configuration finished the test in just under five minutes.
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