To many others interested in Adobe product's ability to use 64 bit architecture,
The information below was shared on the Live Picture list. It came from the Adobe web site. The Live Picture list subscribers include many of the leading photographers around the world.
Hope this information is useful.
Aloha, ev
There are essentially two facets of the G5's 64-bit nature:
1. The ability to process 64 bit data items with the non-Altivec instructions. Photoshop almost never needs to process 64 bit data (pixels are either 8 or 16 bits wide). There's essentially nothing to be gained here. The advantage of the Altivec instructions is not that they can process one data item of 128 bits -- they can't. The Altivec instructions are a big win because they allow processing multiple 8 or 16 bit pixels in parallel.
2. The ability to address more than 4G of memory. Right now, Photoshop can only use 2G of memory, no matter how much is on the machine.
This is so for two reasons:
A. Photoshop's memory pointers are all 32 bits. Converting Photoshop (or almost any other existing large program) to address memory with 64 bit pointers instead of 32 bit ones is a major undertaking.
B. OS X cannot give any individual program more than 2G of memory. The kernel doesn't know how to manage this, and none of the toolbox APIs for graphics, I/O, or anything else, can deal with 64 bit memory addresses.
So the answer to "when will Photoshop be able to take advantage of 64 bit processing"?
1. 64 bit math -- not for the forseeable future, since Photoshop doesn't need 64 bit math.
2. 64 bit memory addressing: some time after Apple supports it.
Here is more information to followup on my previous post concerning 64-bit memory usage with Adobe products on the new G5s.
It comes from the same Live Picture list.
I am running a dual G5 with a full 8GB of RAM under Panther (10.3)
MEMORY USAGE of the G5...
Using the "Activity Monitor" in Panther, TOTAL SYSTEM MEMORY AVAILABLE shows 4GB NOT 8GB. It appears that Apple has not yet fully crossed into true 64bit territory. Presently, there appears to be nothing to be gained by installing more than 4GB in a new G5.
MEMORY USAGE of PHOTOSHOP...
Earlier this month, I asked Adobe two questions about RAM usage in the G5.
Q1 - When will PSD be able to use more than 2GB of RAM ?
The answer below is from Marc Pawliger the head of engineering for the Photoshop team:
"No currently shipping version of OS X - neither 10.2.X nor 10.3 - will
allow Photoshop to address more than 2GB. Apple has stated they plan
to have support for > 2GB processes in a future version of OS X. Note
the OS X kernel can access > 2GB - G5 systems currently support up to
8GB installed - but no single user process can access more than 2GB at
a time."
Q2 - Why does PSD in its "Memory & Image Cache" preference only make available 1667MB (not the full 2GB) from which the usage percent can be selected ?
Again Marc Pawliger:
"OS X 10.2.X and 10.3.X will never allow Photoshop to use more than this.
Photoshop needs to reserve some of the maximum 2GB any application can use
for itself."
So the answer, for now at least, is PSD can only use a theoretical maximum of 2GB but in reality can only access a maximum of approx 1667MB.
I should add, however, that the Dual G5 runs PSD (with its special plug-in) so fast and so efficiently that this amount of RAM doesn't seem to matter. Everything including 1200 pixel brushes work in real time.
(Typical file: 12" x 18", full res 300dpi, CMYK, 27 layers, uses 1.2GB of PSD RAM)
As I said in a post earlier this month, PSD is just now catching up to the performance on big files by using massive amounts of horsepower that we enjoyed with LivePicture seven years ago on relatively modest hardware. LP remains an incredible tool.
And yes LP still works perfectly in the classic layer under Panther just as it did under Jaguar.
Bill Martin's Creative Services Consulting/Networking services and support OS 9.x, X 10.x.x Digital Photography, Audio, Video
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