Still missing my MacPro memory

G

geordisjd

Member
Months ago, I had to "adjust" my MacPro memory in the terminal because Parallels was incompatible with 4GB. Now, it still "sees" only 3 GB. I entered sudo nvram boot-args="" in the terminal and restarted, but it didn't work. How do I regain my lost memory?
 
Keep in mind that any application under OS X is probably only going to be able to access 3GB or so, because OS X on the Intel systems is not fully 64-bit. I may not be right on that, but I read somewhere that unless the OS is 64-bit, apps can only truly access 3GB. This is why Photoshop can only use up to 3GB (although they have a work-around where it used memory above that for scratch functions).
 
Do you mean I shouldn't worry about finding my lost GB and anybody with more than 3GB is wasting money on extra memory?
 
geordisjd said:
Do you mean I shouldn't worry about finding my lost GB and anybody with more than 3GB is wasting money on extra memory?
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I'm saying that right now, until we have 64-bit OS X (Intel-based), that apps aren't going to be able to address more than 3GB, and even then the apps have to be written to do so.

If you go into the Adobe forums, and look into the Photoshop CS3 forum, one of the Adobe developers explained the problems with 64-bit/non 64-bit and 3GB barriers and applications. At this time, Adobe isn't going to go 64-bit, and so Photoshop is still only going to adress 3GB (they have some pseudo-work around to use extra memory as a scratch disk). The decision seemed to be partially they didn't see the majority of users having more than 3GB - 4GB of memory, and partially because Apple didn't have a 64-bit version of Intel-based Tiger/Leopard available.

If you have more than 3GB of memory, go into Photoshop and try to give it more - you can't:



I don't understand all of the mumbo-jumbo behind the limitations, and I'm only bringing up Photoshop because that's a problem I ran into - on my Mac that I am going to be using Photoshop CS3 on, I have 8GB. I'm not bothered by it, but it caught my eye.

Somebody pointed me to this ADC entry on 64-bit Mac OS X (this was about PowerPC G5s):
Tiger features a redesigned kernel and updated system software math libraries specifically for the 64-bit PowerPC G5 processor. The updated kernel delivers the most substantial benefits of 64-bit computing by breaking through the 4GB physical memory limit.
Click to expand...
 
To follow up, you may find this interesting:

Adobe forum thread
Adobe forum thread #2

Some quotes from those threads:

"The 3Gig limit is imposed by the OS. Photoshop does ask the OS to use any other available RAM as a disk cache, which speeds up operations when you exceed the available RAM."

"The maximum addressable RAM is unchanged from CS2 - ~3GB on Mac, 2GB on XP, 3GB with the /3GB switch, ~4GB on XP/Vista x64. If the system has more than 4GB of RAM, we turn on caching on scratch read/writes, which lets the OS use the rest of that RAM for caching our I/O. The
effectiveness on that depends on the OS."

"...we saw no significant performance gains in experiments that we ran to see if being a 64-bit native application would help. The scheme of turning on scratch disk caching when we detect over 4GB of RAM in the system is quite effective, and the loss of performance due to having to move around bigger structures (since pointers are bigger, etc., etc.) offset other performance gains. Note that the different OSes use the extra memory in the system in slightly different ways.

"As for the Macintosh Intel systems, allowed application memory space is the same - approximately 3GB for a 32bit process as for a PPC system."
Click to expand...
 
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