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View Full Version : Memory in pshop....allocation and cache and spec..?



daveseeley
03-07-2005, 08:52 AM
Checked the pshop tutorial and didn't see this...haven't had time to do the pshop testing that Boots was kind enough to send. Just bought another 2 gb of ram to add to my 2.5. I got four 512mb dims from OWC for my 2.5 dual g5. The description I ordered from said they were cas 3.0, but they say cas 2.5 on the modules. Is this a significant downgrade switch?

My system prefs see all four and a half gigs of memory, but when I open photoshop (7 not CS) prefs, the available ram shows as only 1693mb...so that's what photoshop shows as the 100% allocation. Is that the max that shows from the 2gb 32 bit allowance?...or is something not right? I have osx mail, safari and system preferences open, but I'd think that the additional 2.5gb of ram would cover those.

I'm currently using 4 levels of cache....I do big ass images that always exceed ram. What cache level should I use?

Thanks

Dave

daveseeley
03-07-2005, 01:12 PM
Another forum tells me that 2.5 cas is about speed of ram and is an upgrade from 3.0.....though there is some question about whether or not 2.5 will want to live happily together with 3.0 modules.

rwm
03-07-2005, 08:07 PM
Take a look at some of these links. http://www.macgurus.com/forums/showthread.php?t=19546 There are many other factors in determing 'good' RAM it's not just the than CAS.

It is probably best to have matching RAM or at least have them all test "good specs" the same?. But having 2 or more quality sticks of RAM that are a touch different might not play good especially under heavy loads (And sounds like you need/use LOTS of stable RAM) - the different clock cycles, bus speeds, other speeds involved mix get all confused. Like me now. :D - someone other them me would have to explain the technical issues. It's in that link some where. Plus I know really know nada about the G5's.

If you have it try it and if it crashes/won't play good - buy some quality RAM from Gurus. http://www.macgurus.com/productpages/ram/mgram.php

Boots
03-08-2005, 08:05 AM
Hi Dave,
If you look in the "Memory" subsection of System Profiler, you will see each of your individual RAM sticks listed.

Assuming all the installed RAM is properly seen by the system-

On my rig, under "Speed" (of memory), in System Profiler, any CL2.5 RAM is "PC3200U-25330", and any CL3 RAM is "PC3200U-30330".
I'm not sure what the "U" stands for...

The CL2.5 RAM returns slightly faster results in PshopTest; anywhere from .4 seconds to 1.0 seconds faster.

For awhile, I had a mixed installation of 2GB of 30330 and 2GB of 25330. I was having some stability problem with the occaisional kernel panic- once every 3-4 weeks, but I was not able to determine if this was a RAM problem or not.

Now, I have 4GB of entirely 25330 RAM, and time will tell if this has eliminated that occaisional panic problem.

With 4 or more GB of installed RAM in a G5, Photoshop will 'report' anywhere from roughly 1700MB to almost 1840MB of "Available RAM" in "Memory Usage" in the "Memory & Image Cache" preference panel. The figure varies according to how many other applications are running, running background processes, and startup items.

Photoshop can address a maximum of 2048MB of physical RAM currently, but when it 'reports' "Available RAM", it always subtracts what it thinks is the required minimal amount of RAM from 2048MB in order to sustain the operating system. Hence the lower tahn 2GB figure of "Available RAM".

Depending on your hard drive and scratch disk config and setup, setting the "Maximum Used by Photoshop" slider to a percentage higher than 70%, may either increase or decrease the speed of operations. It is a powerful setting, and can over-ride the operating system's normal way of allocating RAM. So you really have to test to determine what's best for your particular setup....
"Starving" the system of available RAM by allocating more than 70% to Photoshop usually slows down the speed of file saves and opening files. But it can increase the overall speed of Photoshop operations; it can become kind of a 'trade-off' situation, which is where the test routine really comes in handy- so you're not just guessing.

An "Image Cache" setting of 8 is better when working large files; it speeds up opening files and other operations a bit also.

daveseeley
03-08-2005, 09:05 AM
Hi Dave,
If you look in the "Memory" subsection of System Profiler, you will see each of your individual RAM sticks listed.

Assuming all the installed RAM is properly seen by the system-

On my rig, under "Speed" (of memory), in System Profiler, any CL2.5 RAM is "PC3200U-25330", and any CL3 RAM is "PC3200U-30330".
I'm not sure what the "U" stands for...

My original apple ram is PC3200U-30330. I have two additional 1gb sticks which show as PC3200U-30440, and all the new CL2.5 sticks show as PC3200U-25330.


For awhile, I had a mixed installation of 2GB of 30330 and 2GB of 25330. I was having some stability problem with the occaisional kernel panic- once every 3-4 weeks, but I was not able to determine if this was a RAM problem or not.

I don't think I've ever had a kernel panic....though I don't know how to ID it. Certainly had perpetual spinning beachballs, and just having an app disapear. Also the finder frozen. I'll look out for new issues with the mixed ram.

Now, I have 4GB of entirely 25330 RAM, and time will tell if this has eliminated that occaisional panic problem.

Let me know!

With 4 or more GB of installed RAM in a G5, Photoshop will 'report' anywhere from roughly 1700MB to almost 1840MB of "Available RAM" in "Memory Usage" in the "Memory & Image Cache" preference panel. The figure varies according to how many other applications are running, running background processes, and startup items.

So far I'm max at 1703mb with safari and mail running.

Depending on your hard drive and scratch disk config and setup, setting the "Maximum Used by Photoshop" slider to a percentage higher than 70%, may either increase or decrease the speed of operations. It is a powerful setting, and can over-ride the operating system's normal way of allocating RAM. So you really have to test to determine what's best for your particular setup....
"Starving" the system of available RAM by allocating more than 70% to Photoshop usually slows down the speed of file saves and opening files. But it can increase the overall speed of Photoshop operations; it can become kind of a 'trade-off' situation, which is where the test routine really comes in handy- so you're not just guessing.

...but wasn't the point of adding ram to make sure the operating system isn't starved as a result of PS? Also, I thought you told me that 100% allocation was better for ps7. Is that not so?


An "Image Cache" setting of 8 is better when working large files; it speeds up opening files and other operations a bit also.

I'll try 8....

Thanks again. I hope to do some ps testing soon.

Boots
03-08-2005, 09:30 AM
I'm no longer sure that a 100% allocation is best with Photoshop. In my testing, I've certainly found it is not necessarily appropriate with PSCS. At the time I originally tested Photoshop 7, I could find no particular configuration of hard drives or RAM where there was a negative affect to allocating 100%- other than slightly slower file open and file save operations, yet overall speed was increased- if you've got enough RAM on-board...and if you've got a really fast scratch disk, it makes up for those slower saves resulting from the 100% allocation.

I've found that it's really the same with PSCS but whether to choose 100% or less or no more than 70% or less than that even, depends on the speed of your scratch disk, and how much total memory is installed.

Your Photoshop speed will increase with your change from 2.5GB installed to 4.5GB installed RAM. File open and saves will be faster, and filters will be slightly faster. All because the OS has more to work with and Photoshop can be given a larger rather than smaller allocation.

TZ
03-08-2005, 09:36 AM
G5 Memory References (http://www.macgurus.com/forums/showpost.php?p=69530&postcount=15)

G5 General References (http://www.macgurus.com/forums/showthread.php?t=19541) - specs, CIP, Developer Notes...