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My 4G RAM Experiment...

H

HO

Senior member
I borrowed 2 DIMMS (Corsair CMX1024-3200C2)
identical to the ones I already have installed. Now I have a total of 4GB of RAM adorning my PC. I Ghosted my clean XP Pro SP2 install onto my HD for a testbed. I added the /3GB switch to the boot.ini file. Windows reports 3.37GB of RAM. Fine.

I loaded up the Photoshop CS2 demo. It reports 1761MB available @ 100% usage. This is the same amount available with only 2GB of RAM installed in the machine, IIRC. I was expecting to see somewhere in the neighborhood of 2600+MB available to Photoshop. CS2 *knows* that it's there, here's a snip from the PS system info:

Physical processor count: 2
Processor speed: 2210 MHz
Built-in memory: 3454 MB
Free memory: 2988 MB
Memory available to Photoshop: 1761 MB
Memory used by Photoshop: 100 %
Image cache levels: 4

Whassup?
__________________
XP Pro
Tyan K8E
Antec P180
X2 4400+
Matrox P650
Atla
 
The program may be limited to that amount. I have 2GB and it says 1762MB available. That may be all that windows will let it have.
 
Just some quick checks:

You have fully updated SP2? (not really likely to be the issue, though)

You get the 3GB option question during boot?

CS2 demo supports the 3GB switch? It's no good telling me that CS does. Does the demo?

Edit: What do you mean by "Windows reports 3.37GB of RAM"? It should report 4GB RAM. Unless you mean 3.37GB available?
RAM is physical memory. It's not "memory" from the applications point of view. So it's got nothing to do with the 3GB switch or the application. (I think you should be able to use the 3GB switch even with 2GB RAM.)
 
Originally posted by: Vee
Just some quick checks:

You have fully updated SP2?

You get the 3GB option question during boot?

CS2 demo supports the 3GB switch? It's no good telling me that CS does. Does the demo?
Click to expand...

I am running SP2. Are there other updates that I need?

I have edited the boot.ini to list XP with the 3G switch as well as without. Other than that, there is no other option question presented...


The CS2 demo is supposedly the full version; my understanding is that it can be liscensed by purchasing a serial number from Adobe. So I assume the answer is yes to the last question. I await your input on the answers to the first two questions.

Thanks.

EDIT: The 3.37 appears in the System properties when right clicking on My Computer and choosing Properties. The BIOS sees all 4G.
 
OK, I think you should get a question during boot if you want to boot with the 3GB switch or standard. Unfortunately I'm on my way out, and in a bit of hurry, so you'll get no further respons from me, for awhile I'm afraid. But for now, I'd say examine the way you added the switch. Maybe it's not entirely correct?
 
Originally posted by: HO
[EDIT: The 3.37 appears in the System properties when right clicking on My Computer and choosing Properties. The BIOS sees all 4G.
Click to expand...

That appears a bit strange. But I have no experience with 4GB PCs.
 
I was told that was not an issue on 64 bit, but i can't confirm till i move my home pc to 64 bit.. i will be trying this weekend..
 
I can just hear them now...
"If you play BF2, 2GB of memory will get by at low res. But if you really want to play well go with 4GB" :laugh:
 
Originally posted by: t3h l337 n3wb
Don't programs in Windows XP have a 2GB limit for memory usage? I think I heard that somewhere.
Click to expand...

Yes, but the "/3GB switch" being referred to above makes it 3GB instead of 2GB. Also, programs that use PAE extensions (mostly things like server-side database software) can address additional memory beyond their 'normal' address space.

With a 64-bit operating system, it should not be a problem; the OS will be able to use practically any amount of RAM (and individual applications will be able to use 4GB or more as well). The virtual addresses that cause problems with accessing the upper parts of the 32-bit memory space are placed in much higher address ranges.
 
Originally posted by: Bozo Galora
there have been at least three threads here recently that hashed all this out
Click to expand...
Specific to Photoshop or just the 4G thing in gereral?

 
i cant even fathom running 4GB of ram just for photo shop. id maybe understand if it was for premier...but i dont know much about editing photos.
 
Originally posted by: NYTRIDR
i cant even fathom running 4GB of ram just for photo shop. id maybe understand if it was for premier...but i dont know much about editing photos.
Click to expand...

I can open 3 normal (for me) layered images and PS will consume all available RAM.

 
Originally posted by: NYTRIDR
i cant even fathom running 4GB of ram just for photo shop. id maybe understand if it was for premier...but i dont know much about editing photos.
Click to expand...
Take an image from a high resolution DSLR (Nikon D2x, Canon 1Ds MkII, or medium format digital back) or a film scan (which has similar effective resolution but typically will be scanned at a much higher DPI), add a few layers and masks, and it's not a hard thing to make 2GB look like child's play.
 
Originally posted by: Vegito
Originally posted by: Vee
Originally posted by: HO
[EDIT: The 3.37 appears in the System properties when right clicking on My Computer and choosing Properties. The BIOS sees all 4G.
Click to expand...

That appears a bit strange. But I have no experience with 4GB PCs.
Click to expand...


Windows will never show 4gb memory

http://pics.bbzzdd.com/users/forcesho/4gb.JPG

on 4gb system, u get low 3's or high 2 with 2 pci express card installed
Click to expand...


Of course. The information in that link is no mystery. I just figured "My computer properties" should recognize that 4GB RAM is installed. But there you go. :-/
 
Lets get the basics straight.

Any Windows32 application is limited to a 2GB virtual space. That is not memory nor RAM. It's the space of numbers available as addresses for the applications executable code and data. As the application asks for memory blocks in this space will be mapped by the OS to a physical location in RAM or in swap area on the hd. Thus any single application can only use less than 2GB memory. The virtual space becomes fragmented so the application runs out of available memory well before 2GB usage.
This is the problem that concerns the /3GB switch. This limits kernel space to 1GB and provides some aware applications with a 3GB virtual space.
It really doesn't have much directly to do with RAM, physical memory. You may need and may use this 3GB switch even if you have only 1Gb or 2GB RAM installed.
AFAIK the switch is only available in XPpro and the 2k server OSes.

BTW, this 2-3GB limit is due to the 32-bit property of the application and OS.

A completely separate issue, Windows is also limited to 4GB physical RAM. This issue is not due to the 32-bit property. It is due to the way Windows translates virtual addresses into physical RAM. You may well use more memory than 4GB but performance will take a huge hit since a good deal of it would be in swap area on hd.
This is the problem that concerns the PAE switch. PAE changes the way Windows translates physical addresses to support up to 64GB physical RAM. How much depends on the version of the server OS and the licence.
PAE can still not give any single application access to more than 2GB memory!
It allows the OS to use more than 4GB RAM to serve the collective memory needs of multiple applications.
AFAIK PAE is incompatible with /3GB.

(For any application to use more than 2-3GB memory under Windows it must abandon the Windows32 program model. It must use the PAE switch and also a memory management API called AWE to do its own custom segmented memory model.)

...And all this tiresome fuss is why we're going 64-bit.
 
HO, I'm sure Adobe would have some instructions/advice on how to apply the /3GB switch for CS. Did you follow those?
 
Vee, thanks for all the info. I found this MS doc that explains the workings of the 3G switch: http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx

Since I couldn't think of anything I hadn't already tried, I rewrote the boot.ini file and now it works--I have 2700MB available to PS @ 100%. Apparently it was user error all along... 🙂

EDIT: even though the 3G switch has technically nothing to do with the amount of installed RAM, the boys and girls at Adobe have done a fine job of letting Photoshop latch on to an extra 1G of RAM when the switch is invoked--as long as 4G of RAM is installed in the machine. Adding the 3G switch *without* the extra RAM does nothing to improve performance... probably has the opposite effect.
 
The improvement factor:

*Time to open 3 images simultaneously for editing (2GB) = 73 seconds
*Time to open the same 3 images simultaneously for editing (4GB) = 35 seconds

Now if I just had a solid state HD for scratch... 🙂
 
Originally posted by: HO
The improvement factor:

*Time to open 3 images simultaneously for editing (2GB) = 73 seconds
*Time to open the same 3 images simultaneously for editing (4GB) = 35 seconds

Now if I just had a solid state HD for scratch... 🙂
Click to expand...

Pls post your boot.ini.
 
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