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Old 08-11-2004, 07:56 PM   #1
cragwolf
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RAM amount not being reported correctly


I'm still feeling my way around Slackware and Linux having only just installed in the past week. I was reading up on some Linux commands, and came across "free". The output of "free -m" was:

Code:
             total       used       free     shared    buffers     cached
Mem:           883        230        652          0         24        114
-/+ buffers/cache:         91        791
Swap:          486          0        486
But I have 2GB of RAM! And I know it works because that's what Windows reports it as. So why is Linux not correctly reporting (or detecting) my RAM amount, and what can I do to fix this? Don't tell me to recompile the kernel. No, I'm kidding, if that's what it takes, then that's what I'll do .. had to happen sooner or later.
 
Old 08-11-2004, 08:05 PM   #2
Mephisto
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To access more than 1GB of physical RAM you do indeed need to recompile the kernel. I don't remember the config option off the top of my head but it would be under Processor Type and functions. High Memory Support or some such. By default it is likely to be set at off. To access above the 1GB mark you will need to compile it with 4GB.

I am a bit confused as to why it is showing 883MB though. Do you have a built in video?

EDIT: I was close "Processor Type and Features" the "High Memory Support" option.
EDIT2: This is the 2.6 Kernel option. I m not sure if it is in the same place in 2.4 though.

Last edited by Mephisto; 08-11-2004 at 08:09 PM.
 
Old 08-11-2004, 09:05 PM   #3
cragwolf
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Thanks. I'm not sure why 883 MB instead of 1GB either. I don't have built in video; I use an nvidia fx5700 graphics card. I will compile the v2.6 kernel. I will read up on how to do that, but just as a general question, so that I know roughly what to expect: when you recompile your kernel, do you have to subsequently reconfigure things like X, CUPS, broadband connection, and so on?
 
Old 08-11-2004, 09:11 PM   #4
Mephisto
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Quote:
Originally posted by cragwolf
... as a general question, so that I know roughly what to expect: when you recompile your kernel, do you have to subsequently reconfigure things like X, CUPS, broadband connection, and so on?
No the version of the kernel should not make effect userspace software as long as you compile the correct options/modules for your hardware and requirements. I suggest reading the 2.6 kernel guide above, as well as the pertinent parts of the 2.4 guide. Pay particular attention to post 15 in the 2.6 thread when it discusses preventing the "blank screen" on compile. This is a common mistake. Incidentally I checked a 2.4 machine and the high memory option is the same.
 
Old 08-11-2004, 09:18 PM   #5
Mephisto
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Also take your time and be patient. If I don't know the precise specs of my hardware I like to have the output of lspci handy on tty2 while I do the configuation on tty1. Another good hint as to what you need is to look at what modules your current, working, kernel is using and build all the modules that are currently being used (lsmod will give you a list of the currently loaded modules).

The one exception to that rule with 2.6 is you do not need SCSI-IDE for your CD burner.
 
Old 08-11-2004, 10:14 PM   #6
carboncopy
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Quote:
Originally posted by cragwolf
Thanks. I'm not sure why 883 MB instead of 1GB either. I don't have built in video; I use an nvidia fx5700 graphics card. I will compile the v2.6 kernel. I will read up on how to do that, but just as a general question, so that I know roughly what to expect: when you recompile your kernel, do you have to subsequently reconfigure things like X, CUPS, broadband connection, and so on?
NO, you don't have to reconfigure ANYTHING at all.
 
Old 08-12-2004, 06:18 AM   #7
cragwolf
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Thanks again, you're all very helpful. I'm planning on doing the recompile on the weekend.
 
Old 09-21-2004, 03:23 PM   #8
benne
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I got the sam problem, though i got 1 gb of ram , not 2.

I run gentoo linux and a manully compiled 2.6 kernel.. Do i need to active big ram suport for 4 gb to get my 1 gb working?
 
Old 09-21-2004, 04:30 PM   #9
shilo
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The docs say that highmem support is fgor 1-4G RAM, but it is really for 883MB-4G. This is an easy recompile, since you are only gonna change one thing. Read up on kernel compiling and be amazed. When you don't change a bunch of stuff, you don't break stuff. A note is that the Con Kolivas patch moves the highmem lower limit up to 1G, since it is common to have exactly 1G RAM.
 
Old 09-21-2004, 04:54 PM   #10
Skazi
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Looks like a good article on HIGHMEM, but I haven't finished reading it yet:

http://kerneltrap.org/node/view/2450
 
Old 09-21-2004, 08:52 PM   #11
sh1ft
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con kolivas has an easy kernel patch for those with only 1gig who do not want the overhead of high memory support:

for 2.6.8.1

its at the top called 1g_lowmem or some such, also patches available for other kernel versions I think.

EDIT: sorry didn't see shilo had already referred to this...
 
Old 09-21-2004, 09:04 PM   #12
xushi
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Is there a version of that for the 2.4.26 (mitt scsi) kernel?

EDIT: ------------------>

Quote:
Con Kolivas patch moves the highmem lower limit up to 1G, since it is common to have exactly 1G RAM.
Iignore the top remark, im Just a little confused, which would you recommend for a person who has 1Gig of ram, to recompile the kernel and set the ram to 1G-4G, or to patch the kernel increasing the lower limit from ~860M to 1G?

Last edited by xushi; 09-21-2004 at 09:12 PM.
 
Old 09-22-2004, 04:49 AM   #13
benne
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Just recompile it. I did that, a kernel patch may mess you r system up. E.g. I use the gentoo sources and the path may be designen for the vanilla sources, it doesnt say..
 
  


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