11", 2 GB + Thunderbolt Display: enough RAM?

Discussion in 'MacBook Air' started by Roman2K~, Dec 3, 2011.

  1. Roman2K~, Dec 3, 2011
    Last edited: Dec 4, 2011

    macrumors 6502a

    I'm contemplating coupling a base 11" i5, only 2 GB of RAM, with a Thunderbolt Display.

    Since the iGPU uses the main memory, how much of the 2 GB is going to be consumed to drive a 2560x1440 display?

    I know it's going to be smooth, but I'm wondering how much RAM would be left to work with before swapping occurs. Especially considering this is normal usage for me (currently on a 4 GB MBA):


    (790 MB wired, a.k.a. non-freeable!)
  2. macrumors 6502

    Swapping will occur but it isn't noticeable at all with the SSD, I have the 2gb of ram model and bI have yet to experience any slowdowns what so ever, I have used it on a 1920x1080 display and it is wonderful. The MBA isn't my only Mac though as I have a MacBook with 5 Gigs of ram , but I use the MBA 90% of the time with no problems as of yet.

    If you really need 4GB of ram go get 4gb of ram, for me as a Student , the base MacBook Air was the most I could afford, and I LOVE it.
  3. macrumors 6502a

    You make a very compelling point about the quick swapping thanks to the SSD.

    I just forced my current MBA into swapping and it's amazingly seamless. I got up to 4.5 GB of swap, lots of page ins / outs, and though it was slower, it was definitely bearable. Almost like all was happening in memory.

    Not even remotely as frustrating as my previous experiences of swapping over HDDs (I've been scarred for life by the first Intel iMac and its 512 MB of memory :rolleyes:).

    Thanks for sharing your experience!
  4. macrumors 6502a

    I guess I'll be able to comment on the matter in two weeks. Both the 11" i5 and TBD are ordered :cool:.
  5. macrumors 65816

    You're dropping $2000 with the idea of using a MacBook Air with a ThunderBolt Display. It amazes me why you won't spend an extra $200 to get the 4GB RAM and instead create a thread asking if you can get by?

    Isn't it worth spending the extra 10% for peace of mind? Particularly when you're asking a non-power notebook to drive 2560 x 1440 pixels?
  6. macrumors 65816


    Agreed. Get 4GB.
  7. macrumors 6502a

    I would agree 100% but I'm getting the cheapest 11" while waiting for the Ivy Bridge line-up. The TBD is a long term investment, the MBA is not (except if 2 GB proves enough and the new line-up turns out disappointing).

    From personal experience, cheaper models have greater resale value proportionally to their original price. At least in France. And I got a fine deal on an open box so I should lose close to nothing comes sell time :D.
  8. macrumors 65816

    Completely understand now. ;)

    As I was reading the OP, I'm thinking "What is wrong with this guy and why isn't anyone recommending 4GB!?!?!?!?!"
  9. macrumors 6502a

    Haha :D. I knew the OP would seem weird without detailing the context but I wanted to focus on the 2 GB vs. 2560x1440.
  10. macrumors 6502a


    You're French and you speak English? Never seen that before. :)
  11. macrumors 68020


    I was going to agree with everyone else but you do make a point. Base models usually sell for more relatively to their original price. I personally wouldn't "wait" for Ivy Bridge though, Sandy Bridge is pretty fast already. I doubt it will be as noticeable as the C2D->SB transition.
  12. macrumors 6502a

    Yep :). Love your signature!

    I'm more concerned about battery life (clock cycle efficiency, power management) than CPU performance. Even an i5 1.6 GHz is going to be plenty (for me) for years, but I expect IB to improve battery life by 20-30%.
  13. macrumors 65816

    The one thing you might want to look out for is if the $999 is the "true" base model. Because I consider the $1200 11" as the base model due to the 128GB and 4GB RAM. In other words, when Ivy Bridge hits, would people quickly dismiss the 64GB and 2GB RAM driving the market and prices down for that model?
  14. Roman2K~, Dec 3, 2011
    Last edited: Dec 3, 2011

    macrumors 6502a

    "Technical" people like us think that. I can only speak for France, but from what I've seen, lots of people (the Joes, or Jeans for that matter ;)) don't think about MacBook Airs in terms of specs. As silly as it sounds, they look at whether a given MBA is latest or last generation, its condition and the size of the screen. The sad truth is they aren't fair about specs like base vs. higher end model (like 1.6/2/64 vs 1.6/4/128), upgrades (BTO like i7) or remaining warranty. I'm currently experiencing this first hand with my late 2010 13" ultimate.
  15. macrumors 6502a

    Today, I received my Thunderbolt Display. What a fine chunk of metal. Almost worth its price once seen and felt in person.

    Good news, the little 2 GB MBA can drive it perfectly fine. Moving windows, animations, Chrome and Safari scrolling, upscaled 1080p, all in parallel, all smooth.

    Example RAM usage while connected to the TBD, playing MP3s via iTunes over Wi-Fi, 720p video paused in VLC in separate space, a few Chrome tabs, one Safari tab, and copying files over Wi-Fi using rsync:


  16. macrumors 68030


    glad you like it..enjoy :)
    Pics of the desk+ display +air maybe?
  17. macrumors Pentium


    Let's see, how much RAM will this use...

    3686400 pixels, at 4 bytes per pixel...

    of course we want double buffered output...

    29,491,200 bytes or just shy of 30 MB for frame buffer memory. Considering the GPU already consumes either 128 MB or 256 MB by default, you have plenty left over for the internal display and heck, a 2nd TB display if you want.

    Really, guys, sweating displaying a desktop is so 1998. My 1996 Matrox Millenium II could push out 1600x1200, and it had 4 MB of WRAM. We're in 2011, displaying a desktop at native resolution is nothing to our hardware today, any hardware.
  18. macrumors regular

    Get the 4GB of ram and wait for a deal if the money is too much. You'll regret it if you don't.
  19. macrumors 6502a


    Get 4GB of RAM
  20. Roman2K~, Dec 14, 2011
    Last edited: Dec 14, 2011

    macrumors 6502a

    I enjoy it very much indeed. Clamshell mode works flawlessly so far. In absolute silence :).

    My current setup is nothing to write home about. Work in progress from leftovers, ghetto style :D. I've taken 2 pictures:


    Thanks for your suggestions, but I was set on (and got) the 2 GB no matter what. It's a matter of resale value ;). And as it turns out, it's enough for me.

    Thanks for having taken the time to do this math. I'm not sure that's all there is to it though.

    I don't know how it works in depth, but I imagine that with the 30 MB of framebuffer, you've got just enough for buffering an image or two to send to the display. If the rendering is being done by the CPU, it's fine.

    In modern OSes, most of the window rendering and animations is done by the GPU. This requires allocating additional memory for the GPU to access and compute from (in addition to the final frame).

    I get your point, but in the case of the HD 3000, there's no dedicated GPU memory, so it borrows from the main memory. My concern was about the 2 GB of main memory minus the share of the GPU.
  21. macrumors 6502

    Glad you have had a similar experience as me with the 2gb, I have yet to experience a slowdown , like a regular HDD laptop would experience. It is very impressive.
  22. macrumors Pentium


    Yep, all there is to a frame buffer. That's how you calculate memory requirements for displaying a desktop resolution. You do know why we don't do it anymore right ? Because frankly it hasn't been required in a quite a long time.

    30 MB is a double buffered, 32 RGBA space. Enough for the displayed image sent to the monitor and the background image that will be the next frame, your working space.

    Compositing is what you're talking about. Yes, it does use buffers on the GPU (in this case, main system RAM) in a modern compositing engine. But again, your GPU has way more memory than the 30 MB required. In fact, looking up the actual specs, the minimum it'll use is 256 MB :

    So you're already losing this memory anyhow. However, you can still do accelerated desktop rendering without using the GPU RAM. The GPU simply processes the pixels before writing them directly to the framebuffer, using the back buffer as its working space. This is how the Matrox Millenium II could achieve 2D accelerated Windows/image rendering on 4 MB WRAM for 1600x1200 resolution.

    Again, you're sweating the little stuff... ;)

    Well, it already "borrows" 256 MB. Might as well put it to good use. ;)

    This is also the reason why you shouldn't bother with clamshell mode. I leave my Air open and toss things like iTunes or Chrome on the internal display while working on my external. Extra pixels are always welcomed and don't even make the thing break a sweat. Why bother to leave them dark ?
  23. macrumors 6502a


    You don't want to be swapping to SSD all the time though. You'll be burning through the program/erase cycles of the NAND chips much more quickly that way.

    On the other hand, this form factor SSD is becoming cheaper now so by the time the drive goes bad they can probably be had for a decent price.

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