Run your Mac up to 40 times faster, increase SSD lifetime with a RAM Disk

“Once upon a time (specifically, for about a year between buying my first laptop in 2006 and the Internet’s October, 1997 arrival in my neck of the (literal) woods) I ran the PowerBook 5300 about 95% on a RAM disk,” Charles Moore reports for TechnologyTell.

“Aside from the benefit of near silent computing, the advantages of using a RAM disk were speed and longer battery runtime. Whatever the PowerBook 5300′s virtues (it did have some), speed wasn’t one of them, so every little bit helped,” Moore reports. “The processor—in that case a 100 MHz Power PC 603e—could reference RAM a lot faster than the 4,200 RPM HDD, and used less battery juice doing it. However, once the Internet arrived here in October, 1997, RAM disk running was pretty much over, at least for everyday computing, and interest in RAM disks began to fade. Apple dropped the Mac OS RAM DIsk creation option from OS X.”

“However, Swiss developer Power APP has just announced the release of RamDisk for Mac [US$8.99], a new utility that the company claims can speed up a Mac by factors of up to 40x, as well as increasing the lifetime of your MacBook’s Solid State Disk,” Moore reports. “As in days of yore, RamDisk creates a virtual drive using the Mac’s RAM, and, of course, today’s Macs give you a lot more RAM to work with. The virtual RamDisk drive can be treated like any drive on the Mac; files and data can be stored, and applications can be installed and run off that drive (although note well that until created data is saved to a physical volume it remains in a perishable state, and will be lost in the event of a power cutoff or unrecoverable crash). ”

Read more in the full article here.

MacDailyNews Note: OS X users can create RAM Disks via the Terminal app for free.

Open Applications > Utilities > Terminal and enter the following command:

diskutil erasevolume HFS+ ‘RAM Disk’ `hdiutil attach -nomount ram://xxxxxxx`

Replace the “x” characters above with the number that represents the desired size for your desired RAM Disk. The size of the disk is based on the number of 512-byte sectors. So, to create a 4 GB RAM Disk in OS X, replace the xxxxxxx’s in the Terminal command above with 8388608 which is the result of (4 * 1024³)/512.

Run the command and you’ll have a 4GB Ram Disk (or whatever size you desire/can afford out of your system’s RAM) mounted on your desktop.

Run apps via RAM and watch them fly! (Or, when you want to show just how fast your Mac is via something like Geekbench, you restart your Mac, create a Ram disk, and run Geekbench off RAM.)

To remove the RAM Disk, just eject it via the Finder as with any other disk.

[UPDATE: 2:40pm EDT: Fixed the formula above.]


  1. Except for very few special use cases, RAM disks are absolutely useless in good virtual memory systems like OS X. RAM disks were just a way to make manual use of the RAM when the OS itself was too stupid to do that on its own.

  2. I used to have a Macintosh quadra av, it had embed audio and video capture, but it was impossible to capture full frame (640×480) full 30fps even with the SCSI drives in that Mac. So I used RAM disk to create a fast disk to capture and then pass it to the hard drive.
    Men, RAM disk was wonderful and I’m glad it’s back. Of course I won’t need it to capture video any more but as a cache for the hard drive will be wonderful.
    Another app from those times was “RAM DOUBLER” from
    Conectrix, there was a PC version also but never worked as fast and smooth as the Mac version. Microsoft later brought that company, which by the way, created the Virtual PC for the Mac ( there was also “soft windows for Mac” but from another company) and Microsoft shut it down and keep the virtual PC software up to today.

    1. I used to have a Quadra 840AV (actually still have it). That thing was so friggin’ awesome at the time. I had mine loaded up to the max with 128MB of RAM (that was at a time when most Macs had 4MB). I remember talking about my Mac and when mentioning the RAM, people would say, “no, that’s you hard drive, how much RAM do you have?” To which I’d respond saying 128MB was my RAM, my hard drive was 2GB internal and 2GB external.

      The funny part about using that Mac was that there was considerable startup time. It needed to do a RAM check to power up, and then the drives themselves had to warm up before they could be used at full speed.

      I’d use Premiere with a huge scratch disk in RAM and when pretty much anything crashed (which it did often), that could set you back hours. That, and backing up nightly to DAT.

      Those were the days.

      1. Ah yes the good ole days- I had a quadra 800 with a 250 MB HD and I think I paid 50$ per meg of RAM to add an extra 8MB for total of 16. It was about a 3000$ computer with 15″ monitor! I remember RAM doubler, Norton utilities and of course Marathon (now on my iPad)…

  3. I don’t see the point of this. I installed 16GB of RAM in my Mac mini for a reason… and that was to allow me to run a lot of apps at the same time, and also use Parallels Desktop very heavily. I bought my MacBook Pro w/retina display with 16GB of RAM for the same reason. The last thing I want to do is hand over a significant amount of that RAM to a RAM disk. No matter how fast an SSD is, whether it’s one of the fancy new PCIe based SSDs, or one connected via SATA, applications will not run any faster than they’re designed to run. A RAM disk will not change that.

    1. For the most part, it’s hard to find a good use for a RAM disk, but it is possible to significantly speed up an app. Pretty much any app that does any disk thrashing will speed up the faster that disk is. Just as an SSD is faster than an HDD, RAM is even faster.

      While a properly written app shouldn’t disk thrash when RAM is available, for a variety of reasons, some do. Those that do will speed up as long as the RAM isn’t being fully consumed by the RAM disk such that virtual memory becomes the bottle neck.

      Additionally, RAM disks allow one to manually decide what will be placed in RAM versus being read/written from SSD or HDD. Essentially for reliability, you don’t want data existing only in RAM, but writing to SSD or HDD may slow down the process. If you’re willing to forgo reliability, you can gain speed in some situations by writing to a RAM disk, and there can be ways to work around the reliability issue.

      Again, this isn’t for everybody and not for all apps and situations, but there are some situations where this could speed things up.

  4. Awesome. Was just looking into setting this up a couple months ago. I decided that to use a RAM Disk effectively, I would need to mount a new RAM Disk and copy my frequently used Apps to it every boot, sym link it with with the Applications and Library folders to use it seamlessly, and back it up back to the hard disk before shutting down. Every piece of it can be done with technology built OS X – but putting it all together well requires a lot of scripting. Was surprised to find no one had made a Mac App to make this kind of setup easy. Judging from this article, the people at Power APP have heard my silent pleas and built the App I was looking for.

  5. That formula seems overly complicated. Just do it the following way:

    diskutil erasevolume HFS+ ‘RAM Disk’ `hdiutil attach -nomount ram://$(expr 512 \* 2048)`

    The first value after “expr” being the desired disk size in MB.

    1. I had to change your expression to:

      diskutil erasevolume HFS+ “RAM Disk” `hdiutil attach -nomount ram://$(expr 2048 \* 2048)`

      (note the double quotes around the name of the disk)

  6. Oh, for heaven’s sake. Just open a terminal window, and run:

    diskutil erasevolume HFS+ “ramdisk” `hdiutil attach -nomount ram://8388608`


  7. RAM disks were popular back in the digital stone age because the “disk” commonly used back then was a floppy.
    Floppies make punch cards seem fast. 😉

    1. How well I remember swapping floppies – until I bought my first hard drive, a Photon 40 for $700. It had a whopping 40Mb of storage. ($700, 40Mb – no typos in the previous lines.) A real bargain at the time.

      1. I can confirm; no typo there. The 40MB Jasmine SCSI hard drive I bought in 1988 for my Fat Mac cost $1500. It wasn’t an expense: with the freelance translation work it enabled me to do, it paid for itself in mere months…

Reader Feedback

This site uses Akismet to reduce spam. Learn how your comment data is processed.