LinuxQuestions.org
Register a domain and help support LQ
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Distributions > Slackware
User Name
Password
Slackware This Forum is for the discussion of Slackware Linux.

Notices

Reply
 
Search this Thread
Old 05-19-2006, 02:16 PM   #1
masterross
Member
 
Registered: Nov 2005
Distribution: Slack 10.2, CentOS 4.x
Posts: 83

Rep: Reputation: 17
3.6GB RAM instead of 4GB ???


hi there,

just setuped new server and i see that availeble RAM is only 3.6GB instead of 4GB??

any idea why?

thanks
 
Old 05-19-2006, 03:12 PM   #2
Wells
Member
 
Registered: Nov 2004
Location: Florida, USA
Distribution: Debian, Redhat
Posts: 383

Rep: Reputation: 31
Just as a guess, this is going to be an AMD64 system. Take a look in bios for something called "memory hole" and play with that setting. Typically, if you set that to use a hardware mapped memory hole the problem should go away.

Very often this setting will be found somewhere under the northbridge settings of the bios.
 
Old 05-19-2006, 03:28 PM   #3
masterross
Member
 
Registered: Nov 2005
Distribution: Slack 10.2, CentOS 4.x
Posts: 83

Original Poster
Rep: Reputation: 17
actually it's dual Xeon
i'll check in bios

thx
 
Old 05-19-2006, 03:45 PM   #4
Wells
Member
 
Registered: Nov 2004
Location: Florida, USA
Distribution: Debian, Redhat
Posts: 383

Rep: Reputation: 31
So that you know, the reason that this is happening is that x86 architecture pushes the PCI Option ROMs into the space just below the 4gb point in memory. So, when you actually have enough memory to reach the 4gb point, you lose some of that memory because it is being taken up by ROMs instead. Some bios's have the capability to remap the RAM above this point so that you can actually use it.
 
Old 05-20-2006, 04:11 PM   #5
Mircale
LQ Newbie
 
Registered: May 2006
Posts: 1

Rep: Reputation: 0
Quote:
Originally Posted by masterross
hi there,

just setuped new server and i see that availeble RAM is only 3.6GB instead of 4GB??

any idea why?
I had just the same few days ago.
While BIOS POST reported 4 gigs available the kernel uses only 3,5 gigs (just like 4096 - 512 is 3584)
I even thought it's broken memory .

The problem solved after I've enabled support for 64G of memory in the kernel. All 4G were there.

HTH
 
Old 09-03-2008, 02:39 PM   #6
brooky9999
Member
 
Registered: May 2006
Location: Marlow, UK
Distribution: Slackware 12.2
Posts: 232

Rep: Reputation: 30
Hi,

My Slack 12.1 box (running 2.6.25.4) cannot see all 4Gb of RAM. I have enabled High Mem (64Gb) in the kernel and recompiled, but still when I run:

Code:
Free -m
It just says Mem: Total = 2915.

The BIOS sees 4096Mb.

Any thoughts?


Mark.
 
Old 09-03-2008, 02:50 PM   #7
keefaz
Senior Member
 
Registered: Mar 2004
Distribution: Slackware
Posts: 4,454

Rep: Reputation: 96
Are you sure you replaced the old kernel with your new one ?
A way to quick check:
Code:
zcat /proc/config.gz | grep HIGHMEM
 
Old 09-03-2008, 03:02 PM   #8
brooky9999
Member
 
Registered: May 2006
Location: Marlow, UK
Distribution: Slackware 12.2
Posts: 232

Rep: Reputation: 30
Hi Keefaz,

I though I had... but when I grep config.gz, I get both options:

# CONFIG_NOHIGHMEM is not set
# CONFIG_HIGHMEM4G is not set
CONFIG_HIGHMEM64G=y
CONFIG_HIGHMEM=y

Is that correct?


M.
 
Old 09-03-2008, 03:07 PM   #9
keefaz
Senior Member
 
Registered: Mar 2004
Distribution: Slackware
Posts: 4,454

Rep: Reputation: 96
Yes, it is your new kernel (default has not CONFIG_HIGHMEM64G=y IIRC)
 
Old 09-03-2008, 03:10 PM   #10
brooky9999
Member
 
Registered: May 2006
Location: Marlow, UK
Distribution: Slackware 12.2
Posts: 232

Rep: Reputation: 30
Hmmm... exactly. Now I'm stumped :-(

Thanks anyway,


M.
 
Old 09-03-2008, 03:44 PM   #11
keefaz
Senior Member
 
Registered: Mar 2004
Distribution: Slackware
Posts: 4,454

Rep: Reputation: 96
Maybe post infos about your motherboard and processor, by luck another one with the same config may have solved this issue
 
Old 09-04-2008, 08:07 AM   #12
symatic
Member
 
Registered: May 2007
Distribution: Slackware
Posts: 242

Rep: Reputation: 32
Look at this wonderful utilization of ram. Sorry continue on:
Code:
symatic@secular:~$ free -m
             total       used       free     shared    buffers     cached
Mem:          1010        982         27          0        141        498
-/+ buffers/cache:        342        667
Swap:          486          2        483
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
REDHAT 9 SMP and more than 4GB RAM dukeoflinux Linux - Hardware 4 08-22-2007 10:33 PM
Does FC 5 64x support 4GB RAM? NAC Fedora 0 05-10-2006 11:51 PM
utilize 4gb of ram cynick Linux - General 2 04-20-2006 11:42 AM
What if you had 2GB RAM and 4GB HD? AC97Conquerer General 21 03-28-2005 07:21 PM
4GB RAM not showing eddie0uk Linux - Hardware 5 03-12-2005 07:08 AM


All times are GMT -5. The time now is 11:16 PM.

Main Menu
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration