BIOS detects 4 GB RAM, but kernel does not

Hello,

On a dual core Pentium 4 EM64T machine (Intel Desktop Board D915GAV), we used four 1GB RAM (DDR 400) modules. The BIOS (EV91510A.86A.0444) detected all the four 1 GB modules, but once the OS is booted, only ~3.1GB is available for usage (from dmesg: "Memory: 3210516k-3267772k available"; see below). The kernel used is version 2.6.9-22.ELsmp coming with 'CentOS release 4.2 Final'. The four RAM modules have been tested OK with the 'memtest'.

Using "mem=4096m" while booting the kernel also did not help. Searched through the old messages and it looks like in most of the cases enabling some memory-hole related option in BIOS is suggested, but in this case probably the BIOS is fine. Not sure if some kernel configuration option is missing or if someother version of the kernel needs to be used.

This being a 64 bit machine, we expected memory-remap to be happening. Is there a way in which ~900 MB of RAM can be made usable? Any pointers will be of great help.

Please let me know if more information is needed than the following transcripts (-proc-iomem and dmesg):

$ moreproc-iomem 00000000-0009fbff : System RAM 0009fc00-0009ffff : reserved 000a0000-000bffff : Video RAM area 000c0000-000c7fff : Video ROM 000f0000-000fffff : System ROM 00100000-c772fbff : System RAM 00100000-0030754e : Kernel code 0030754f-0044680d : Kernel data c772fc00-c772ffff : ACPI Non-volatile Storage c7730000-c773ffff : ACPI Tables c7740000-c77effff : ACPI Non-volatile Storage c77f0000-c77fffff : reserved cfb00000-cfbfffff : PCI Bus #05 cfc00000-cfcfffff : PCI Bus #04 cfd00000-cfdfffff : PCI Bus #03 cfe00000-cfefffff : PCI Bus #02 cff00000-cfffffff : PCI Bus #01 d0000000-dfffffff : 0000:00:02.0 e0000000-efffffff : reserved fed13000-fed19fff : reserved fed1c000-fed9ffff : reserved ff43bc00-ff43bfff : 0000:00:1d.7 ff43bc00-ff43bfff : ehcihcd ff43c000-ff43ffff : 0000:00:1b.0 ff43c000-ff43ffff : ICH HD audio ff440000-ff47ffff : 0000:00:02.0 ff480000-ff4fffff : 0000:00:02.0 ff500000-ff500fff : 0000:06:08.0 ff500000-ff500fff : e100 ff600000-ff6fffff : PCI Bus #05 ff700000-ff7fffff : PCI Bus #04 ff800000-ff8fffff : PCI Bus #03 ff900000-ff9fffff : PCI Bus #02 ffa00000-ffafffff : PCI Bus #01

$ dmesg Bootdata ok (command line is ro root=LABEL=-1 mem=4096m rhgb quiet) 3.4.4 20050721 (Red Hat 3.4.4-2)) #1 SMP Sat Oct 8 21:32:36 BST 2005 BIOS-provided physical RAM map: BIOS-e820: 0000000000000000 - 000000000009fc00 (usable) BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved) BIOS-e820: 00000000000e6000 - 0000000000100000 (reserved) BIOS-e820: 0000000000100000 - 00000000c772fc00 (usable) BIOS-e820: 00000000c772fc00 - 00000000c7730000 (ACPI NVS) BIOS-e820: 00000000c7730000 - 00000000c7740000 (ACPI data) BIOS-e820: 00000000c7740000 - 00000000c77f0000 (ACPI NVS) BIOS-e820: 00000000c77f0000 - 00000000c7800000 (reserved) BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved) BIOS-e820: 00000000fed13000 - 00000000fed1a000 (reserved) BIOS-e820: 00000000fed1c000 - 00000000feda0000 (reserved) 0x00000000000f4eb0 0x00000000c7730000 0x00000000c7730200 0x00000000c7730390 0x00000000c7730400 0x00000000c7736020 0x00000000c77360c0 0x00000000c77360f4 0x0000000000000000 No NUMA configuration found Faking a node at 0000000000000000-00000000c772f000 Bootmem setup node 0 0000000000000000-00000000c772f000 No mptable found. On node 0 totalpages: 8168 plus 143 DMA zone: 4096 pages, LIFO batch:1 Normal zone: 812847 pages, LIFO batch:16 HighMem zone: 0 pages, LIFO batch:1 DMI 2.3 present. ACPI: PM-Timer IO Port: 0x408 ACPI: Local APIC address 0xfee00000 ACPI: LAPIC (acpiid0x01 lapicid0x00 enabled) Processor #0 15:4 APIC version 16 ACPI: LAPIC (acpiid0x02 lapicid0x01 enabled) Processor #1 15:4 APIC version 16 ACPI: LAPICNMI (acpiid0x01 dfl dfl lint0x1) ACPI: LAPICNMI (acpiid0x02 dfl dfl lint0x1) Setting APIC routing to flat ACPI: IOAPIC (id0x02 address0xfec00000 gsibase0) IOAPIC0: apicid 2, version 32, address 0xfec00000, GSI 0-23 ACPI: INTSRCOVR (bus 0 busirq 0 globalirq 2 dfl dfl) ACPI: INTSRCOVR (bus 0 busirq 9 globalirq 9 high level) ACPI: IRQ0 used by override. ACPI: IRQ2 used by override. ACPI: IRQ9 used by override. Using ACPI (MADT) for SMP configuration information Checking aperture... Built 1 zonelists Kernel command line: ro root=LABEL=-1 mem=4096m rhgb quiet console=tty0 Initializing CPU#0 PID hash table entries: 4096 (order: 12, 131072 bytes) time.c: Using 3.579545 MHz PM timer. time.c: Detected 3000.257 MHz processor. Console: colour VGA+ 80x25 Dentry cache hash table entries: 524288 (order: 10, 4194304 bytes) Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes) Memory: 3210516k-3267772k available (2077k kernel code, 0k reserved, 1276k data, 188k init) Calibrating delay loop... 5914.62 BogoMIPS (lpj=2957312) Security Scaffold v1.0.0 initialized SELinux: Initializing. SELinux: Starting in permissive mode There is already a security framework initialized, registersecurity failed. selinuxregistersecurity: Registering secondary module capability Capability LSM initialized as secondary Mount-cache hash table entries: 256 (order: 0, 4096 bytes) CPU: Trace cache: 12K uops, L1 D cache: 16K CPU: L2 cache: 2048K using mwait in idle threads. CPU0: Initial APIC ID: 0, Physical Processor ID: 0 Using IO APIC NMI watchdog CPU: Trace cache: 12K uops, L1 D cache: 16K CPU: L2 cache: 2048K CPU0: Initial APIC ID: 0, Physical Processor ID: 0 CPU0: Intel(R) Pentium(R) 4 CPU 3.00GHz stepping 03 per-CPU timeslice cutoff: 615.86 usecs. task migration cache decay timeout: 1 msecs. Booting processor 1-1 rip 6000 rsp 100042d5f58 Initializing CPU#1 Calibrating delay loop... 5996.54 BogoMIPS (lpj=2998272) CPU: Trace cache: 12K uops, L1 D cache: 16K CPU: L2 cache: 2048K CPU1: Initial APIC ID: 1, Physical Processor ID: 0 Intel(R) Pentium(R) 4 CPU 3.00GHz stepping 03 Total of 2 processors activated (11911.16 BogoMIPS). activating NMI Watchdog ... done. testing NMI watchdog ... OK. Using local APIC timer interrupts. Detected 12.501 MHz APIC timer. checking TSC synchronization across 2 CPUs: pbutted. Brought up 2 CPUs Disabling vsyscall due to use of PM timer time.c: Using PM based timekeeping. checking if image is initramfs... it is NET: Registered protocol family 16 PCI: Using configuration type 1 PCI: Using MMCONFIG at e0000000 mtrr: v2.0 (20020519) ACPI: Subsystem revision 20040816 ACPI: Interpreter enabled ACPI: Using IOAPIC for interrupt routing ACPI: PCI Root Bridge PCI0 (00:00) PCI: Probing PCI hardware (bus 00) PCI: Ignoring BAR0-3 of IDE controller 0000:00:1f.1 PCI: Transparent bridge - 0000:00:1e.0 ACPI: PCI Interrupt Routing Table -SB.PCI0.PRT ACPI: PCI Interrupt Routing Table -SB.PCI0.PEGP.PRT ACPI: PCI Interrupt Routing Table -SB.PCI0.P0P2.PRT ACPI: Power Resource URP1 (off) ACPI: Power Resource FDDP (off) ACPI: Power Resource LPTP (off) ACPI: Power Resource URP2 (off) ACPI: PCI Interrupt Routing Table -SB.PCI0.PEX1.PRT ACPI: PCI Interrupt Routing Table -SB.PCI0.PEX2.PRT ACPI: PCI Interrupt Routing Table -SB.PCI0.PEX3.PRT ACPI: PCI Interrupt Routing Table -SB.PCI0.PEX4.PRT ACPI: PCI Interrupt Link LNKA (IRQs 3 4 5 6 7 9 10 *11 12 14 15) ACPI: PCI Interrupt Link LNKB (IRQs 3 4 5 6 7 9 10 11 12 14 15) *0, disabled. ACPI: PCI Interrupt Link LNKC (IRQs 3 4 *5 6 7 9 10 11 12 14 15) ACPI: PCI Interrupt Link LNKD (IRQs 3 4 5 6 7 9 *10 11 12 14 15) ACPI: PCI Interrupt Link LNKE (IRQs *3 4 5 6 7 9 10 11 12 14 15) ACPI: PCI Interrupt Link LNKF (IRQs 3 4 5 6 7 9 10 11 12 14 15) *0, disabled. ACPI: PCI Interrupt Link LNKG (IRQs 3 4 5 6 7 9 10 11 12 14 15) *0, disabled. ACPI: PCI Interrupt Link LNKH (IRQs 3 4 5 6 7 *9 10 11 12 14 15) usbcore: registered new driver usbfs usbcore: registered new driver hub PCI: Using ACPI for IRQ routing PCI-DMA: Disabling IOMMU. IA32 emulation $Id: sysia32.c,v 1.32 2002-03-24 13:02:28 ak Exp $ audit: initializing netlink socket (disabled) audit(1153910756.923:1): initialized Total HugeTLB memory allocated, 0 VFS: Disk quotas dquot6.5.1 Dquot-cache hash table entries: 512 (order 0, 4096 bytes) SELinux: Registering netfilter hooks Initializing Cryptographic API ksign: Installing public key data Loading keyring - Added public key 860947C6651999BC - User ID: CentOS (Kernel Module GPG key) pcihotplug: PCI Hot Plug PCI Core version: 0.5 ACPI: Processor CPU1 (supports C1, 8 throttling states) ACPI: Processor CPU2 (supports C1, 8 throttling states) Real Time Clock Driver v1.12 Linux agpgart interface v0.100 (c) Dave Jones serio: i8042 AUX port at 0x60,0x64 irq 12 serio: i8042 KBD port at 0x60,0x64 irq 1 Serial: 8250-16550 driver $Revision: 1.90 $ 8 ports, IRQ sharing enabled ttyS0 at I-O 0x3f8 (irq = 4) is a 16550A RAMDISK driver initialized: 16 RAM disks of 16384K size 1024 blocksize divert: not allocating divertblk for non-ethernet device lo Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2 ide: buttuming 33MHz system bus speed for PIO modes; override with idebus=xx ICH6: IDE controller at PCI slot 0000:00:1f.1 ICH6: chipset revision 3 ICH6: not 100% native mode: will probe irqs later ide0: BM-DMA at 0xffa0-0xffa7, BIOS settings: hda:DMA, hdb:pio ide1: BM-DMA at 0xffa8-0xffaf, BIOS settings: hdc:pio, hdd:pio Probing IDE interface ide0... hda: SONY DVD RW DW-G120A, ATAPI CD-DVD-ROM drive Using cfq io scheduler ide0 at 0x1f0-0x1f7,0x3f6 on irq 14 Probing IDE interface ide1... Probing IDE interface ide1... Probing IDE interface ide2... Probing IDE interface ide3... Probing IDE interface ide4... Probing IDE interface ide5... hda: ATAPI 48X DVD-ROM DVD-R-RAM CD-R-RW drive, 2048kB Cache, UDMA(66) Uniform CD-ROM driver Revision: 3.20 ide-floppy driver 0.99.newide usbcore: registered new driver hiddev usbcore: registered new driver usbhid drivers-usb-input-hid-core.c: v2.0:USB HID core driver mice: PS-2 mouse device common for all mice input: AT Translated Set 2 keyboard on isa0060-serio0 input: ImPS-2 Logitech Wheel Mouse on isa0060-serio1 md: md driver 0.90.0 MAXMDDEVS=256, MDSBDISKS=27 NET: Registered protocol family 2 IP: routing cache hash table of 16384 buckets, 256Kbytes TCP: Hash tables configured (established 262144 bind 65536) Initializing IPsec netlink socket NET: Registered protocol family 1 NET: Registered protocol family 17 ACPI: (supports S0 S1 S4 S5) ACPI wakeup devices: PEGP P0P2 AC97 USB0 USB1 USB2 USB3 USB7 UAR1 PEX1 PEX2 PEX3 PEX4 AZAL PWRB Freeing unused kernel memory: 188k freed SCSI subsystem initialized libata version 1.11 loaded. atapiix version 1.03 PCI: Setting latency timer of device 0000:00:1f.2 to 64 ata1: SATA max UDMA-133 cmd 0xE800 ctl 0xE402 bmdma 0xD800 irq 193 ata2: SATA max UDMA-133 cmd 0xE000 ctl 0xDC02 bmdma 0xD808 irq 193 ata1: dev 0 cfg 49:2f00 82:346b 83:7d01 84:4023 85:3468 plus 1 86:3c01 87:4023 88:207f ata1: dev 0 ATA, max UDMA-133, 312581808 sectors: lba48 ata1: dev 0 configured for UDMA-133 scsi0 : atapiix ATA: abnormal status 0x7F on port 0xE007 ata2: disabling port scsi1 : atapiix Vendor: ATA Model: ST3160212AS Rev: 3.AA Type: Direct-Access ANSI SCSI revision: 05 SCSI device sda: 312581808 512-byte hdwr sectors (160042 MB) SCSI device sda: drive cache: write back Attached scsi disk sda at scsi0, channel 0, id 0, lun 0 kjournald starting. Commit interval 5 seconds EXT3-fs: mounted filesystem with ordered data mode. SELinux: Disabled at runtime. SELinux: Unregistering netfilter hooks inserting floppy driver for 2.6.9-22.ELsmp Floppy drive(s): fd0 is 1.44M FDC 0 is a post-1991 82077 e100: Intel(R) PRO-100 Network Driver, 3.4.8-k2-NAPI e100: Copyright(c) 1999-2005 Intel Corporation divert: allocating divertblk for eth0 e100: eth0: e100probe: addr 0xff500000, irq 209, MAC addr 00:13:20:CA:C8:C9 PCI: Setting latency timer of device 0000:00:1b.0 to 64 ehcihcd 0000:00:1d.7: EHCI Host Controller PCI: Setting latency timer of device 0000:00:1d.7 to 64 ehcihcd 0000:00:1d.7: irq 201, pci mem ffffff0000006c00 ehcihcd 0000:00:1d.7: new USB bus registered, buttigned bus number 1 PCI: cache line size of 128 is not supported by device 0000:00:1d.7 ehcihcd 0000:00:1d.7: USB 2.0 enabled, EHCI 1.00, driver 2004-May-10 hub 1-0:1.0: USB hub found hub 1-0:1.0: 8 ports detected USB Universal Host Controller Interface driver v2.2 uhcihcd 0000:00:1d.0: UHCI Host Controller PCI: Setting latency timer of device 0000:00:1d.0 to 64 uhcihcd 0000:00:1d.0: irq 201, io base 000000000000c800 uhcihcd 0000:00:1d.0: new USB bus registered, buttigned bus number 2 hub 2-0:1.0: USB hub found hub 2-0:1.0: 2 ports detected uhcihcd 0000:00:1d.1: UHCI Host Controller PCI: Setting latency timer of device 0000:00:1d.1 to 64 uhcihcd 0000:00:1d.1: irq 193, io base 000000000000cc00 uhcihcd 0000:00:1d.1: new USB bus registered, buttigned bus number 3 hub 3-0:1.0: USB hub found hub 3-0:1.0: 2 ports detected uhcihcd 0000:00:1d.2: UHCI Host Controller PCI: Setting latency timer of device 0000:00:1d.2 to 64 uhcihcd 0000:00:1d.2: irq 185, io base 000000000000d000 uhcihcd 0000:00:1d.2: new USB bus registered, buttigned bus number 4 hub 4-0:1.0: USB hub found hub 4-0:1.0: 2 ports detected uhcihcd 0000:00:1d.3: UHCI Host Controller PCI: Setting latency timer of device 0000:00:1d.3 to 64 uhcihcd 0000:00:1d.3: irq 168 plus 1, io base 000000000000d400 uhcihcd 0000:00:1d.3: new USB bus registered, buttigned bus number 5 hub 5-0:1.0: USB hub found hub 5-0:1.0: 2 ports detected md: Autodetecting RAID arrays. md: autorun ... md: ... autorun DONE. ACPI: Power Button (FF) PWRF EXT3 FS on sda1, internal journal device-mapper: 4.4.0-ioctl (2005-01-12) initialised: device-mapper: dm-multipath version 1.0.4 loaded cdrom: open failed. kjournald starting. Commit interval 5 seconds EXT3 FS on sda7, internal journal EXT3-fs: mounted filesystem with ordered data mode. kjournald starting. Commit interval 5 seconds EXT3 FS on sda2, internal journal EXT3-fs: mounted filesystem with ordered data mode. kjournald starting. Commit interval 5 seconds EXT3 FS on sda3, internal journal EXT3-fs: mounted filesystem with ordered data mode. kjournald starting. Commit interval 5 seconds EXT3 FS on sda5, internal journal EXT3-fs: mounted filesystem with ordered data mode. NET: Registered protocol family 10 Disabled Privacy Extensions on device ffffffff803f9de0(lo) IPv6 over IPv4 tunneling driver divert: not allocating divertblk for non-ethernet device sit0 mtrr: type mismatch for d0000000,10000000 old: write-back new: write-combining Adding 2096440k swap ondev-sda6. Priority:-1 extents:1 iptables: (C) 2000-2002 Netfilter core team iptables: (C) 2000-2002 Netfilter core team e100: eth0: e100watchdog: link up, 100Mbps, full-duplex parport0: PC-style at 0x378 PCSPP,TRISTATE,EPP lp0: using parport0 (polling). lp0: console ready eth0: no IPv6 routers present mtrr: type mismatch for d0000000,10000000 old: write-back new: write-combining

Sorry about cross-posting; was not sure about the group to which this can be asked.

Thanks in advance, Ravi.