2009MP: 6GB Vs 8GB; triple Vs dual channels: PS4 tests

Discussion in 'Mac Pro' started by Loa, Jun 30, 2009.

  1. Loa
    macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #1
    Hello,

    I ran some tests on my 2009 Quad Nehalem to try and determine what was up with the triple Vs dual memory "brouhaha".

    I posted the results as a new thread because I think it will be useful information for a lot of quad owners, but it was originally going to be a reply to this thread: http://forums.macrumors.com/showthread.php?t=735845

    Here we go. Tesselator suggested 3 tests that could show the differences in speed between triple and dual channel bandwidth.

    So I did them, 10 times each. I could have gone on, but the results were very very stable after the first 2 attempts.

    Set-up: a 40Mpx, 16bit image (8000*5000). First test it was simply filled white; second test: black; and third test a black to white gradient. I added a fourth test, using a real (photo) 12Mpx RAW image from my Nikon D300.

    I created (took a while!) an action with 350 repetitions of "duplicate layer" and "delete layer", followed by a red fill to let me know the action was done. The same action was used in all four tests.

    The computer was restarted before each of the four tests, which may explain the irregularities on the first 1-2 attempts. Nothing else but PS4 was launched.

    The results are interesting:

    [​IMG]

    We can clearly see that the simple white and black fills show a speed difference of around 10%.

    We can also clearly see that this difference disappears when a more complex image is used. The use of more complex images represents a much more realistical use of PS.

    _________________________________________

    To make things even more realistic, I also tested RetouchActions's speed test on my own 12Mpx image. I use nearly all of the operations of that action on a daily basis, so it's a lot more representative of the work I do on PS.

    Here are the results:

    [​IMG]

    The results are clear: 11% increase in performance using 8GB of ram (Vs 6GB) when working on a 12Mpx image.

    Added info: number of page-outs after running the 10 test series (after about 45 minutes of intense PS work):
    -17K when using 6GB (1.7K page-out avg).
    -10K when using 8GB (1K page-out avg).

    For me the results are definitive: unless I plan on working only with full black or full white images (not even black and white!), having 8GB is better, even when working on smallish 12Mpx files. I imagine the differences would have been even greater using bigger file sizes of actual complex images.

    _______________________________________

    What would now be interesting: someone with a 2009MP Octo doing the same tests at 12GB and 16GB.

    I'm waiting for reasons why my tests were not good! :-D

    Loa
     
  2. macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #2
    Good work.

    But you were getting pageouts during the tests? If so that would seem to nullify all your efforts.
    I have 12GB RAM and I have to try real hard and do crazy shirt to get any to happen at all.
     
  3. macrumors 604

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #3
    Could this be due to the 4 Gig RAM limit on CS4?

    Or is that limit imaginary?
     
  4. Loa
    thread starter macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #4
    Yes and no: it shows that even if PS has to use a HDD as scratch, you're still a winner by having 8GB.

    Also, most quad users won't be willing to pay the very steep price for 12GB of ram.

    And finally, if a 12Mpx image forces some pageouts on a 8GB system, let alone a 6GB, any thought that a 6GB would be faster in PS is ridiculous. In other words: if 8GB is not enough to handle a 12Mpx image in PS, a 6GB system won't be able to handle any useful or practical size of an image at all.

    Now as I said, I'd be very curious to see, on a 2009 octo, how a 12GB (three 2GB chips on each CPU) Vs 16GB (four 2GB chips on each CPU) would turn out. Maybe that much ram would prevent page-outs.

    But in the end, if you use PS a lot on a quad 2009, 8GB is better than 6GB.

    Loa
     
  5. Loa
    thread starter macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #5
    The limit is actually 3GB, but anything over that will be used (handled by the OS) before PS is forced to the hard drive as scratch disk.

    So having lots of ram is very useful even if PS4 cannot use more than 3GB itself: Mac OS X handles the extra ram to give PS4 maximal perfomance.

    As it's been said in other threads: it's always better to use extra ram, regardless of its speed, instead of going to your HDD with anything extra that PS4 might need.

    Loa
     
  6. macrumors regular

    Joined:
    Nov 23, 2008
    #6
    how wel does your quad & 8gig ram handles a 1 too 3 gig file in PS? can you try one? :)


    i'm working with largeformat scans here and really getting stuck with my imac 24" & 4gig ram
    (working with a 8000 * 10000 px image)


    want a MP now.. but can't pick one: quad with 8gig ram or octo 2,26 with 12gig ram

    my mind is going crazy.. or more ram or more cpu speed :confused:
     
  7. macrumors member

    Shawny D

    Joined:
    May 13, 2009
    #7
    Hahaha, I saw "PS4" and actually thought you meant "PlayStation 4" for all of 2 seconds. :p

    As you were.
     
  8. macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #8
    I don't think this is correct. But maybe you could explain it to me (us).

    AFAIK Adobe hasn't told us how it works or how it's supposed to work.
    So without extensive testing which I'll assume no one has ever done
    and published, everyone is just guessing at how it works.

    I had envisioned two separate systems of what we might commonly
    refer to as VM. One was the scratch file PS uses after the 3GB limit.
    I had assumed it would ALWAYS go to the drive after the 3GB was
    used up and also that it was 3GB per image document. Then the
    second system that the OS handles as you put it, is the Undos,
    History States, and Cache Levels which may not all fit into RAM
    - especially with multiple documents opened and being worked on.

    Since the later are parts of the application environment the OS can
    deal with those. This would also seem to imply that one must tune
    the PS settings for the amount of RAM they have
    . The former 3GB
    limit, is a hard-wired limit so to speak and when it's used up would
    imply the PS has no other choice but to go to disk - the OS can't
    magically extend this limit.

    All of this seems to be supported by my testing so far. Could you clarify?


    A few interesting observational "facts" I've discovered about PS CS3/4:
    • I can edit in PS for days with 14 ~ 24 MPx images and never see any
      significant pageouts - always far less than 1MB total. I have 12GB RAM.

    • When PS writes to it's scratch disk no pageout activity is recorded.

    • PS itself is slower than any scratch disk you're likely use. PS's peak
      usage of the scratch drive is about 40 MB/s Write and 28 MB/s read.
      It's average is MUCH less - about 7 MB/s write and 3 MB/s read.
      This is due to PS's display code and not the storage device I/O speed.
      I have a 2006 MP octad 2.66 with a 7300GT card.

    • In typical use PS never EVER uses it's scratch disk. You have to do
      something crazy to get it to happen. You have to create a single
      document larger than 3GB.


    .
     
  9. Loa
    thread starter macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #9
    Well I won't be able to explain it to you at an architectural or procedural level, but I'll do it on a pragmatic level: when dealing with a complex image (not a simple fill), a number of different and complex layers and a varied series of operations on those layers, PS4 works faster with 8GB than with 6GB. (As my graph shows.)

    Others have done the same tests, including your very best friend Diglloyd. ;-)

    So if the OS is not preventing disk usage by "directing" all that over-3GB data to excess ram, how can we explain that performance increase?

    I understand your 4 facts, but we still need to explain the significant performance gain from going from 6GB to 8GB, using a 12Mpx image.

    Loa
     
  10. Loa
    thread starter macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #10
    I'm willing to try it, but you'll have to be more specific than "handle". What operations do you usually use, and would you want me to time how long it takes? (Also, do you use 8, 16 or 32 bits images?)

    Well as it stand right now, PS4 is not programmed to handle a lot of cores. There's a very good chance, though, that PS5 (coming out when???) will.

    Loa
     
  11. macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #11
    Huh? No, no. You're misunderstanding the question. I already understand the performance gains. You were getting pageouts. That blows the entire test for me. But that's not my question. You said:

    "The limit is actually 3GB, but anything over that will be used (handled by
    the OS) before PS is forced to the hard drive as scratch disk.
    "

    This doesn't jive with what I think I know and it sounded like you might know more - so I thought I would ask. Again to be clear, my question isn't about your tests but rather memory management and PS. :)
     
  12. macrumors regular

    Joined:
    Nov 23, 2008
    #12
    oh notting fancy really
    this is my workflow:
    PS&Bridge are open, sometimes flexcolor too
    i start with a 460mb 16bit tiff
    normaly i copy my background layer once
    some selections copyed to a new layer ( lets say 3 selections of about 20% of the image and 1 selection of 40% of the image)
    and the usual fine tuning adjustment layers (one color balance, 3 curves with a mask and 1 curve for the whole image)


    so at the final stages my filee is about 2-3 gig

    my imac just gets it hard when i pull those final 2 or 3 adjustment layers or when i need to adjust a certain area of my image


    you see it's just normal postprocessing (not batching automatic filters :p) and was wondering is those new MP kept up with it.
    it's not really timing how much sec it takes to save a file but wether it keeps working smooth with a 2 gig tiff



    however, if i read the above.. the problem should be the big file size + 3gb memory cap?!?!?
     
  13. Loa
    thread starter macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #13
    No: I understood perfectly. I even said I couldn't give you a "technical" answer. Verifying the PS4 performance of a quad under triple or dual channel (6GB or 8GB) was my only intention.

    As for the pageouts: I already explained why it's really not a problem, but also that it further validates the 8GB choice over the 6GB on a quad. If a "smallish" 12Mpx file forces page-outs with 8GB, there is no way to justify going to 6GB for PS4 on a quad. Period.

    My knowledge is purely pragmatic: I've seen it, even tested it. My only explanation is purely logical. I'll spell it out more clearly:
    -PS4 cannot handle more than 3GB of ram.
    -Adding more ram beyond that limit increases PS4's performance.
    -Thus: something is using that extra memory to "help" PS4.

    I can't imagine that "something" being anything else than the OS.

    I too would like to know exactly why, with full details. But I'm a lot more interested in real-world results than explanations, so I'm not going to be the one that's going to google info until I get a complete picture!

    However you or someone else might explain it, adding more ram (even at the cost of triple memory channel) means more performance in PS4. If it's not done by the OS preventing scratch/VM usage, I don't know how it could be done.

    I'm also very curious to see someone with a 2009MP octo doing equivalent tests with triple/dual memory channels. Maybe those tests would shed more light on PS4's memory management.

    Loa
     
  14. Loa
    thread starter macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #14
    Interesting results. I created the file by blowing up one of my images to your dimensions, then adding the layers and adjustment layers. Initial 16bit TIFF file size 460MB; final file size: 2.66GB.

    Everything went "silky smooth": all masks I added to the adjustment layers were instantaneous, no delays or slow downs. No delay while adjusting the adjustment layers either. Using brushes or dodge/burn tools was as fast as usual.

    Then I thought about using the smear tool on the background layer. Lol. Not a good idea. Don't try it on your iMac! I used a 2500px soft (gradient) round brush size and pulled a large smear. That was X minutes ago: it's not done yet. hahaha (see P.S.)

    All my 8 cores (4 cores with 2 "hyper"threads means 8 core % on your menu bar) are running between 30% to 50%. I'm not sure more cores would help, but maybe someone else can answer that.

    Interesting part: during all those operations, I didn't get a single page-out despite the huge file size.

    All in all, using the operations you stated, I didn't see anything different than usual: everything was instant.

    So unless you want to SMEAR, a 2.66 quad with 8GB of ram will serve you well.

    Loa

    P.S. I force quit PS after 15 minutes of this smear not completing... I could see the smear itself, but it would not stop working. :)
     
  15. macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #15
    OK.

    Hehehe, Pageouts are always a problem. For me this would justify 12GB instead of 6 or 8. Probably
    8 isn't going to make enough of a difference over 6 - only eliminate your ability to capitalize on triple
    channel RAM accesses.


    OK. But let's be clear about one thing for this explanation. PS can't use more than 3GB for an image
    ever. It immediately hits the scratch disk as soon as the image + layers hit over 3GB. Until we get PS 12
    (PS 11 is still 32Bit) this will remain true unfortunately. :(


    Me too. I wanna know. I wanna hear it from Adobe. I want the explanation because with that knowledge
    I can get the best "real-world results" possible. :)
     
  16. Loa
    thread starter macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #16
    While page-outs are a problem for performance, they're not a problem for my test. They not a problem precisely because going for 12GB is not an option. 8GB = 150$, 12GB = 500$.

    I agree.

    I haven't checked myself.

    But, the fact remains that more ram helps PS4, even beyond 3GB. Thus the OS has to help with memory management. Deduction at work!

    Which was my point to begin with.

    Not sure you need it for performance: it's not like we have a lot of options! We already know that 8GB is better than anything smaller. All we need now is a rich guy with 10-12-14-16GB of ram in a quad, running the same tests! Then we'll know when (if?) the performance gains peak.

    Practical knowledge can sometimes be just as good as theoretical knowledge. Sometimes even better, especially when talking about complex systems like computers. If I had done nothing but read tech specs on the way Nehalem handles RAM, I would have gotten 6GB, not knowing that it would have slowed me down by 10% in PS4 (over the 8GB, oh-so-slow dual channel)...

    Loa
     
  17. macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #17
    True, true. But I think we have too many options. That's why I want Adobe's explanation.

    We have up to 1000 possible History States, 8 levels of Cache, From 90 to 3072 MB of document space, OpenGL offloading (somehow??), The Bigger Blocks plug-in, and then the (probably outdated or moot) Adobe policy to partition for the scratch area. UG! Hy head hurts just thinking of that list. I've gone insane (as you can probably tell!) trying to figure out the best combination of them.


    PS: 12GB is only "not an option" if the user is stuck on a 2009 quad system. Apple blew chunks on this one IMO. The chipset on the 09's can support many MANY more DIMMs than that! I think it was up to 144 GB. :D
     
  18. macrumors 6502a

    Joined:
    Aug 31, 2004
    #18
    We could do 12GB in dual and triple channel on a 8 core 2009 MP with 8 memory slots. 6 2GB in triple channel mode and then 4 2GB and 4 1GB which should give 12gb in dual channel mode.

    I do have a 2009 8 core MP and I do have 8 2GB DIMMS and of course the 6 1GB's that came with it. So I could get 12GB in both dual and triple channel modes. I just don't own or have PS4 to do these tests (nor am I familiar with PS4, or any photoshop really). I guess I could probably download a demo, but not knowing the software would make it hard.
     
  19. macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #19
    Yeah. It might be fun tho! But for the original discussion PS was only one case in point. Tests could run on anything really. Here's the original thread: http://forums.macrumors.com/showthread.php?t=735845


    I wanted Apple to offer '09 Mac Pros that configured more like this:

    [​IMG]

    :D
     
  20. Loa
    thread starter macrumors 65816

    Loa

    Joined:
    May 5, 2003
    Location:
    Québec
    #20
    Ya, it would probably be hard... Do you know anyone around you that is familiar with PS4??


    Hehe, hackintosh it!

    Loa
     
  21. macrumors G4

    Joined:
    May 6, 2008
    #21
    Dell? :eek: :p
     
  22. macrumors 601

    Tesselator

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    Japan
  23. macrumors G4

    Joined:
    May 6, 2008
    #23
  24. macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #24
    Oh, you were saying "Dell?" as a possibility not asking if that WAS a Dell board.... (?).

    Yeah... True. Dell workstations and servers are nice. Their home PCs are total crap. The span of between 3 and 8 years ago their prices were pretty good too. This year I've seen some people showing that Dell is now as or more ridiculous than Apple tho - and that's baaaad. :(

    So I think if I want a system with 18 RAM slots and dual procs I'm going to have to hit the parts shops. I don't feel like paying Dell $5000 extra to assemble and test it for me. ;)


    Here's the post that goes with that slide-show BTW: http://www.anandtech.com/weblog/showpost.aspx?i=481
     
  25. macrumors 6502

    Joined:
    Jan 16, 2008
    Location:
    near Cambridge
    #25
    It is not a Dell board. Dell attach the second processor via a daughter board which also has the associated RAM slots (on the T7500 and T5500 at least). They, like Apple, like to have a bit of proprietaryness (if there is such a word).
    Unless it is a Dell server - I don't know what they have in them.

    Dell's dual processor machines are expensive, cheaper than Apple but still expensive versus building one yourself but they do negotiate on price and when they eventually hit Dell Outlet with 35% discount they will be almost cheap.
     

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