CS vs V7 test times for varying amounts of free RAM

Discussion in 'Photoshop Tutorials' started by Bill Hilton, Nov 9, 2003.

  1. Bill Hilton

    Bill Hilton Guest

    I posted in a different thread about my concerns regarding how much RAM CS
    devours when you open a file. Specifically, compared to V7 a 111 MB file
    starts with 262 MB scratch space in V7 but 720 MB in CS (in a box with 1205 MB
    assigned to Photoshop). I thought this would prove to be a real problem for
    speed, especially for people with smaller amounts of RAM since they'd be
    working off the scratch disk after a couple of moves.

    I ran some tests on large files (film scans from 113 MB to 555 MB) and posted
    the results on the "CS vs V7 -- test times for large files" thread. CS was
    still faster than V7 in those tests.

    For this thread I used a much smaller file, a typical 6 Mpix digital camera
    tiff of 18 MB, and I varied the amount of RAM available from 1,205 MB down to
    the minimum amount implied by the 192 MB figure on the box, ie, 96 MB. I ran a
    simple action that does 5 ops (levels, curves, hue/sat, resize to print at 300
    ppi, USM at 150/1.5/2).

    The results were very interesting and suggest that CS has a much more
    sophisticated memory management scheme than V7 does. Basically if you have a
    LOT of RAM it will scarf up a big chunk upon opening the file, but if you have
    a lot less RAM it will scale down accordingly, which is much smarter than what
    V7 did.

    Bottom line, CS is faster even with relatively small amounts of RAM because
    it's smart enough to scale back the memory requirements. So the concerns I
    expressed in the earlier threads are not a problem. Nice job, designers.

    Here's the test data that led me to that conclusion.

    On this machine I have 1.5 GB of RAM with 86% assigned to Photoshop, so 1205 MB
    available in the Preferences box. I decided to check for systems with 1.5 and
    1 GB and 768, 512, 384, 256 and 192 MB of total RAM, using the Photoshop
    default value of 50% for each one (or as close as I could get), so ended up
    checking speed with amounts of RAM varying from 96 - 1205 MB assigned to
    Photoshop (I couldn't set exact numbers since my min increment was 14 MB, so I
    picked the closest value for available RAM).

    The two most important things I found were 1) at all memory sizes CS was faster
    and 2) V7 needed the same amount of RAM for opening the file in every case (146
    MB) but the CS allocation was dynamic, lessening as the amount of memory
    dropped. Specifically, with 1205 MB free CS took 601 MB when loading the 18 MB
    file (hence my original concern), but with only 98 MB of memory free CS dropped
    the allocation to only 68 MB, less than half what V7 needs. So my main concern
    about CS being a memory hog and needing to work off disk early in the flow
    wasn't valid for systems with smaller amounts of RAM.

    Here's the actual data (I hope it formats OK, it's from an Excel spreadsheet).
    As you can see with plenty of RAM CS runs this simple action in 5 seconds, V7
    in 13 seconds. Dropping the amount of RAM to 256 MB starts to slow things down
    as the program needs to go to disk to complete the tasks (the final scratch
    size for V7 was 388 MB for all sizes, for CS it varied from 891 for the most
    memory to 310 MB for the smallest memory).

    V 7 CS V7 / CS

    Memory (MB) time/secs time/secs
    ------------------- ---------------- -------------

    96 (98) 62 49 127%
    128 (140) 43 30 143%
    192 (196) 32 19 168%
    256 (252) 26 14 186%
    384 (378) 13 5 260%
    512 (518) 13 5 260%
    750 (756) 13 5 260%
    1205 13 5 260%

    My conclusion after all these tests here and on larger files is that CS is
    faster across the board and has a more sophisticated memory management scheme
    that does indeed eat up a lot of RAM *if you have it* but obviously knows how
    to use this RAM for higher performance.

    That's *my* last test for awhile :)

    Bill Hilton, Nov 9, 2003
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