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Old 07-16-2003, 06:15 PM   #1
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memory > 1GB

I have a RedHat 7.2 running 2.4.18-17.7.x. The box had 1GB of memory. I added another 512MB memory and the bios recognized the ram but linux does not. What do I need to do to get linux to recognize this additional memory?

Old 07-16-2003, 06:52 PM   #2
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Welcome to,

In the kernel configuration, "Processor type and features"->"high memory" must be enabled.

Last edited by zmedico; 07-16-2003 at 06:57 PM.
Old 07-17-2003, 02:05 AM   #3
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Hi zmedico also thank you.
I've never tried kernel configuration, would you direct a little how to access to it? Thank you
Old 07-17-2003, 06:54 AM   #4
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Old 07-17-2003, 07:39 AM   #5
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There are some instructions for compiling the kernel in /usr/src/linux/README. Usually it's something like this:

cd /usr/src/linux
make xconfig
# edit Makefile (you can add a EXTRAVERSION indentifier)
make dep
make bzImage
make modules
make modules_install
# copy your kernel and set up boot loader
Old 07-21-2003, 06:27 PM   #6
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HIGHMEM kernel won't boot

I have never built any kernels, so I started by building a kernel which I could successfully boot. Then I turned on HIGHMEM in this kernel:

diff .config-custom .config
< # CONFIG_NOHIGHMEM is not set
> # CONFIG_HIGHMEM4G is not set

Now I have an unbootable kernel. It finds the 1.5GB ram, but it fails before initrd is run. Any ideas? I am trying to enable HIGHMEM without the HIGHMEM4G and seeing if that makes a difference. I really need this extra ram for EDA/CAD tools.

Thanks for your help.

Loading lnx-2418-177xHM......................
Linux version 2.4.18-17.7.x.HM (root@mux) (gcc version 2.96 20000731 (Red Hat Li
nux 7.1 2.96-98)) #7 Mon Jul 21 14:45:25 PDT 2003
BIOS-provided physical RAM map:
BIOS-e820: 0000000000000000 - 00000000000a0000 (usable)
BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 000000005fff0000 (usable)
BIOS-e820: 000000005fff0000 - 000000005fff3000 (ACPI NVS)
BIOS-e820: 000000005fff3000 - 0000000060000000 (ACPI data)
BIOS-e820: 00000000ffb00000 - 0000000100000000 (reserved)
639MB HIGHMEM available.
896MB LOWMEM available.
On node 0 totalpages: 393200
zone(0): 4096 pages.
zone(1): 225280 pages.
zone(2): 163824 pages.
Kernel command line: auto BOOT_IMAGE=lnx-2418-177xHM ro root=302 BOOT_FILE=/boot
/bzImage-2.4.18-17.7.x.HM console=ttyS0,9600 console=tty1
Initializing CPU#0
Detected 2399.756 MHz processor.
Console: colour VGA+ 80x25
Calibrating delay loop... 4784.12 BogoMIPS
Memory: 1543924k/1572800k available (1141k kernel code, 24268k reserved, 947k da
ta, 116k init, 655296k highmem)
Dentry cache hash table entries: 262144 (order: 9, 2097152 bytes)
Inode cache hash table entries: 131072 (order: 8, 1048576 bytes)
Mount cache hash table entries: 32768 (order: 6, 262144 bytes)
Buffer cache hash table entries: 131072 (order: 7, 524288 bytes)
Page-cache hash table entries: 524288 (order: 9, 2097152 bytes)
CPU: L1 I cache: 0K, L1 D cache: 8K
CPU: L2 cache: 512K
Intel machine check architecture supported.
Intel machine check reporting enabled on CPU#0.
CPU: Intel(R) Pentium(R) 4 CPU 2.40GHz stepping 04
Enabling fast FPU save and restore... done.
Enabling unmasked SIMD FPU exception support... done.
Checking 'hlt' instruction... OK.
Checking for popad bug... OK.
POSIX conformance testing by UNIFIX
mtrr: v1.40 (20010327) Richard Gooch (
mtrr: detected mtrr type: Intel
PCI: PCI BIOS revision 2.10 entry at 0xfb360, last bus=2
PCI: Using configuration type 1
PCI: Probing PCI hardware
Transparent bridge - Intel Corp. 82801BA/CA/DB PCI Bridge
PCI: Using IRQ router PIIX [8086/2440] at 00:1f.0
isapnp: Scanning for PnP cards...
isapnp: No Plug & Play device found
Linux NET4.0 for Linux 2.4
Based upon Swansea University Computer Society NET3.039
Initializing RT netlink socket
apm: BIOS version 1.2 Flags 0x07 (Driver version 1.16)
Starting kswapd
allocated 64 pages and 64 bhs reserved for the highmem bounces
VFS: Diskquotas version dquot_6.5.0 initialized
Detected PS/2 Mouse Port.
pty: 512 Unix98 ptys configured
Serial driver version 5.05c (2001-07-08) with MANY_PORTS MULTIPORT SHARE_IRQ SER
ttyS0 at 0x03f8 (irq = 4) is a 16550A
ttyS1 at 0x02f8 (irq = 3) is a 16550A
Real Time Clock Driver v1.10e
block: 1024 slots per queue, batch=256
Uniform Multi-Platform E-IDE driver Revision: 6.31
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
PIIX4: IDE controller on PCI bus 00 dev f9
PIIX4: chipset revision 5
PIIX4: not 100% native mode: will probe irqs later
ide0: BM-DMA at 0xf000-0xf007, BIOS settings: hdaMA, hdbio
ide1: BM-DMA at 0xf008-0xf00f, BIOS settings: hdcMA, hddio
hda: IC35L080AVVA07-0, ATA DISK drive
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
ide1 at 0x170-0x177,0x376 on irq 15
blk: queue c035ef24, I/O limit 4095Mb (mask 0xffffffff)
blk: queue c035ef24, I/O limit 4095Mb (mask 0xffffffff)
hda: 160836480 sectors (82348 MB) w/1863KiB Cache, CHS=10011/255/63, UDMA(100)
ide-floppy driver 0.99.newide
Partition check:
hda: hda1 hda2
Floppy drive(s): fd0 is 1.44M
FDC 0 is a post-1991 82077
NET4: Frame Diverter 0.46
RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize
ide-floppy driver 0.99.newide
md: md driver 0.90.0 MAX_MD_DEVS=256, MD_SB_DISKS=27
md: Autodetecting RAID arrays.
md: autorun ...
md: ... autorun DONE.
NET4: Linux TCP/IP 1.0 for NET4.0
IP Protocols: ICMP, UDP, TCP, IGMP
IP: routing cache hash table of 16384 buckets, 128Kbytes
TCP: Hash tables configured (established 262144 bind 65536)
Linux IP multicast router 0.06 plus PIM-SM
NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
RAMDISK: Compressed image found at block 0
Freeing initrd memory: 115k freed
VFS: Mounted root (ext2 filesystem).
VFS: Mounted root (ext2 filesystem) readonly.
Trying to move old root to /initrd ... okay
Freeing unused kernel memory: 116k freed
Old 07-21-2003, 09:41 PM   #7
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I hope you made a boot disk. You may need it to do the steps below.

You forget one more step. You need to make a ram disk image of your compiled kernel.

Type mkinitrd new_module_directory new_image_file

Then redo your boot loader configuration file to include your ramdisk file for the re-compiled kernel. Its best to have your orginal in the boot loader with your re-compiled kernel. After your re-compile kernel works perfectly, you can remove the orginal kernel from the boot loader. Also you may need to specify the size of ram disk if you used the kernel defaults. The kernel sometimes defaults to 4 megabytes. You can specify it by including
append = "ramdisk_size = size_of_ramdisk_in_bytes" for lilo. You can also type ramdisk_size = size_of_ramdisk_in_bytes at the boot loader menu. You can try 32000 or higher.

A summary of can be found:
Old 07-21-2003, 10:52 PM   #8
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here is a post i made with a step by step and with an explanation for every step...i couldn't seem to make it much more easier than this, so maybe this may help you out.
the second link that electro gave you is basically just as easy, so i think you can get what you want done with either or
Old 07-22-2003, 05:25 PM   #9
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memory > 1GB (kernel build)

I think my mistake was using the redhat kernel packages to build a kernel. It is impossible to generate their kernel with what they supply. I downloaded tha latest stable kernel, 2.4.21, from and it was trivial to build a working kernel. I added hi mem support and that works too. I am a happy camper and so are my engineers.

Thanks for your help!
Old 07-22-2003, 11:14 PM   #10
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memory > 1GB? Man, I want his box.

Trade ya.
Old 07-22-2003, 11:19 PM   #11
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K like I said im new to linux...and all this reading about configuring the kernel?? that is bloody scary...


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