I am looking into getting a new Macbook Pro (hopefully they'll have late 2013 models). I currently use my early 2011 Macbook for iOS app programming and light graphic design work with Pixelmator. I can't remember when, but I think when I upgraded to Mountain Lion all programs now take a little longer (too long, imo) to launch.

For future reference, I was wondering what affects app launch times the most? Is it the processor, RAM or hard drive/SSD? Right now my Macbook's got 2.4Ghz Core 2 Duo, 8GB DDR3 and a 250GB hard drive.

4 Answers 4


Until the software is loaded in to the RAM it is your Hard drive that is the bottleneck.

So using SSD you will gain some speed, but make sure you keep 20% free space on the disk.

Once the software is in your RAM it is the combination of the processor (CPU) and the RAM, assuming you have sufficient RAM so not to have to share it with SSD.

After that it is the software it self that slows things down by bad design, bad drivers, or needing lots of other cross functional activity (other programs) to operate.

You can find the details of shut down and start up in your Console


  • Do you have a reference for the "keep 20% free space" claim? That seems rather arbitrary.
    – Dan J
    Jul 26, 2013 at 16:27
  • 1
    There is a good rule of thumb, and actual data report on that anandtech.com/show/6489/playing-with-op saying that a minimum of 10% is required, 15% recommended and 20% almost optimal for access speed.
    – Ruskes
    Jul 26, 2013 at 17:17

The hard drive is the only one that noticeably slows down app launching.

With RAM, there's no noticeable difference unless you already have many programs open and running.

With CPUs you'll only have one core involved in opening an app, so the differences are tiny even if you're making a large improvement.

The payoff with large amounts of RAM and faster CPUs come after the app is open, but mostly that payoff is only seen when you're multitasking or working with large media files.

  • Just between the hard drive performance and the RAM performance, there is an often forgotten factor impacting the time to load an application: the performance of the OS (I/O cache, drivers: read…). This is exactly what is describing the OP.
    – dan
    Jul 26, 2013 at 23:25

SSD/HD speed will impact boot times of apps the most.

  • FWIW, I can launch Photoshop in Jul 26, 2013 at 15:30

I had a MBP with 8 Gig RAM and conventional HD. After replacing the RAM to 16 I had a minor (if at all) improvement it time lag when opening an application. I then replaced the HDD with a SSD and the time lag almost disappeared. So the speed of going to disk to going to RAM seems to be a major issue, and the benefits of a SSD (i.e. a much faster disk) are by a mile the greatest improvement in application loading times. I did not try to overclock the CPU, but I doubt it would have made a major impact, or any impact comparable of moving to SSD.

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