Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Installed memory ≠ usable size?
Special Forums Hardware Filesystems, Disks and Memory Installed memory ≠ usable size? Post 302333051 by CRGreathouse on Friday 10th of July 2009 04:40:07 PM
Old 07-10-2009
Quote:
Originally Posted by otheus
It seems like you don't have a real problem, and that you were asking a theoretical question -- like fact-checking GeekSqaud personnel.
I'm currently eating all of my memory and would like to get the last half-gig. What's more, I'd like to know if I'd be able to double the memory further (buying 4x2GB, since my current setup is full at 4x1GB). So no, it's not theoretical.

Quote:
Originally Posted by otheus
Do you or do you know what's eating your top in .5 GB of memory?
I don't understand why we don't understand each other on this point. I have a 64-bit processor and a 64-bit operating system; I should have no trouble addressing 128 GB. Video memory only reduces currently-available memory if you've used up your addressing limit. So when I had 2 GB and was uncontroversially below my addressing limit, I could see all 2 GB (precisely 2048 MB). Video mapping did not reduce the memory at all.

But now 512 MB are not showing up. The possibilities, as I see them:
1. The OS can only address 32 bits, so only 3.5 GB can be used.
2. The processor can only address 32 bits, so only 3.5 GB can be used.
3. The motherboard can only address 32 bits, so only 3.5 GB can be used.
4. The BIOS is misconfigured to address only 32 bits, so only 3.5 GB can be used.
5. The BIOS is misconfigured in some other way that causes only 3.5 GB to show up.
6. The RAM is bad in some bizarre way that causes only 3.5 GB to be usable.
7. 4 GB are available, but for some reason the tools I'm using (ps, gnome-system-monitor, the BIOS) only see 3.3 to 3.5 GB.
8. Something else is wrong.

#1 and #2 clearly don't apply to me: the OS is 64-bit and the processor, a Phenom II, is also 64-bit. I don't think that #4 is possible. I've looked through the BIOS settings pretty carefully and didn't see anything, but I concede that #5 is possible. #6 and #7 seem absurd. #8 is always a possibility.

What do you think?

Quote:
Originally Posted by otheus
Can you check if it's the video?
I know of no way to do this.

Quote:
Originally Posted by otheus
A 32-bit processor can natively and directly address 4 GB of memory. Since the 8086 architecture allowed for a "segment" address combined with an actual memory pointer, the x86 architecture theoretically maintains the ability to address more memory than this.
As I have an x86_64 (aka AMD64) processor rather than the classic x86, I don't think this is particularly relevant. Of course the microarchitecture is similar, but I don't think there's any disagreement as to the chip's ability to work with more than (say) 8 GB of memory.

Quote:
Originally Posted by otheus
I doubt it hard to believe that a 64-bit chip would be able to address more memory.
I don't follow...?
 

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

How to get amount of memory installed.

Hi! I'm not a UNIX fanatic but I like using it for the Oracle database since it's not stable in the Windows NT environment (what is?). Problem: Is there any command to show me the amount of installed physical-memory in the machine? Is there some other way to show the processes which uses... (4 Replies)
Discussion started by: elgholm
4 Replies

2. UNIX for Dummies Questions & Answers

Size of Installed RAM ?

Is it possible from the command line, or by looking at one of the log files to find out the amount of RAM installed on my SCO Unix 5.05 Server? I also need to find out H/Disk size and Processor speed but I think i'll do a search of the forums for those ones. Thanks RamblasPro (2 Replies)
Discussion started by: RamblasPro
2 Replies

3. UNIX for Advanced & Expert Users

memory size under AIX

Hi, how to know size of physical memory under AIX ? Many thanks. PS : man -k memory man : 0703-310 Fichier man introuvable. uname -a AIX server1 1 5 005202DF4C00 (3 Replies)
Discussion started by: big123456
3 Replies

4. Shell Programming and Scripting

User perl to get memory installed in a machine

I currently have a statistics gathering script i run on my Linux servers. One of the stat i gather is total memory in the machine. The script is all perl with the exception of gathering the memory for that i use the following command: $ram = (`cat /proc/meminfo | grep "MemTotal" | awk... (1 Reply)
Discussion started by: insania
1 Replies

5. UNIX for Advanced & Expert Users

Out of Memory error when free memory size is large

I was running a program and it stopped and showed "Out of Memory!". at that time, the RAM used by this process is around 4G and the free memory size of the machine is around 30G. Does anybody know what maybe the reason? this program is written with Perl. the OS of the machine is Solaris U8. And I... (1 Reply)
Discussion started by: lilili07
1 Replies

6. Solaris

Memory or CPU size

Is there a command or file I can look at that tells me how much real memory a machine has? A little background. In my shop we run a bunch of java programs, sometimes some of these jobs have config definitions that call for 2G. I would like to know how many I can run before I exhaust rescources. Any... (12 Replies)
Discussion started by: Harleyrci
12 Replies

7. UNIX for Dummies Questions & Answers

Getting file size from memory

i want to avoid writing to a file on the disk. i'd like to do this in memory. i have a situation where i'm running cat file.txt | head -l 2024 > /tmp/data.txt now, i check the size of the data.txt by doing a "du -sh /tmp/data.txt how can i get the size of "head -l 2024" WITHOUT having to... (2 Replies)
Discussion started by: SkySmart
2 Replies

8. Solaris

T5220 How to determine physical memory installed?

Hi, looking to upgrade memory on a pair of T5220's from 32GB to 64GB. Cannot determine current DIMM size and slots used. i.e. not sure if Qty 16 x 2GB or Qty 8 x 4GB. If there are no empty slots, i need to go with higher density DIMMs and retire exsisting the 2GB prtdiag follows. #... (3 Replies)
Discussion started by: edrew
3 Replies

9. Programming

Size of memory used by a program

Hello, Here is a portion of my code: a=(int *) malloc(dim*dim*sizeof(int)); b=(int *) malloc(dim*dim*sizeof(int)); c=(int *) malloc(dim*dim*sizeof(int)); for(i=0;i<dim;i++) for(j=0;j<dim;j++) c= rand(); for(i=0;i<dim;i++) for(j=0;j<dim;j++) b=rand(); ... (6 Replies)
Discussion started by: chercheur111
6 Replies

10. AIX

Installed Memory 32GB but shows only 16GB

Hello facing this problem in VIOS installed memory shows 32GB Installed system memory: 32 GB (32768 MB) Configurable system memory: 16 GB (16384 MB) Current memory available: 2.23 GB (2288 MB) Pending memory available: 2.23 GB (2288 MB) Reserved firmware memory: 560 MB ... (8 Replies)
Discussion started by: filosophizer
8 Replies
All times are GMT -4. The time now is 02:54 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy