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P8SC8 - 4G ram seen in the BIOS, only 3 available

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October 20, 2008 6:55:26 PM

Hello all,

this is my first post on this forum (I tried the search engine to find something related but I found nothing relevant).

I've a supermicro server with a motherboard P8SC8. I recently upgraded form 1GB (2*512) to 4GB (4*1G : max supported memory on this platform refering the vendor website).
Something strange occured :

The bios tells me :

Total Physical Memory 4,194,304K
Total System Resources 1,048,576K
Total Available Memory 3,136,512K


Does anybody knows why 1GB his sucked by "Total System Resources".

Bios has been upgraded to last up to date version, I also tried to reset bios to default but I still got the problem.

The Debian running on the machine see the physical 4*1GB memory modules
dmidecode --type 17
# dmidecode 2.8
SMBIOS 2.3 present.

Handle 0x0025, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0024
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 1024 MB
Form Factor: DIMM
Set: None
Locator: DIMM#1
Bank Locator: Bank0/1
Type: SDRAM
Type Detail: Synchronous
Speed: Unknown
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

Handle 0x0026, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0024
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 1024 MB
Form Factor: DIMM
Set: None
Locator: DIMM#2
Bank Locator: Bank2/3
Type: SDRAM
Type Detail: Synchronous
Speed: Unknown
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

Handle 0x0027, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0024
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 1024 MB
Form Factor: DIMM
Set: None
Locator: DIMM#3
Bank Locator: Bank4/5
Type: SDRAM
Type Detail: Synchronous
Speed: Unknown
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

Handle 0x0028, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0024
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 1024 MB
Form Factor: DIMM
Set: None
Locator: DIMM#4
Bank Locator: Bank6/7
Type: SDRAM
Type Detail: Synchronous
Speed: Unknown
Manufacturer: None
Serial Number: None
Asset Tag: None
Part Number: None

Wrong DMI structures length: 1415 bytes announced, structures occupy 1406 bytes.


But still see 3GB
└─# free
total used free shared buffers cached
Mem: 3115228 276892 2838336 0 18720 181572
-/+ buffers/cache: 76600 3038628
Swap: 979956 0 979956


Anyone can help ?

Thanks.

More about : p8sc8 ram bios

Anonymous
a b } Memory
a b V Motherboard
October 20, 2008 7:05:59 PM

If i'm correct your still running windows right?

32 bit windows only can address a little over 3 GB of ram

so right there thats your issue if it is a windows OS

Google is good :) 
October 20, 2008 7:15:32 PM

Quote:
If i'm correct your still running windows right?

32 bit windows only can address a little over 3 GB of ram

so right there thats your issue if it is a windows OS

Google is good :) 



sounds like you're using a 32-bit version of windows. if that's the case, then you'll only be able to see at most 3.25GB of your ram regardless of how much you have. and subtract your video card's ram from that 3.25GB.
Related resources
October 20, 2008 7:20:10 PM

2 things here, as previously mentioned, 32 bit os will limit you to about 3 gig.

2nd.. your mobo supports a max of 4 gig. that means that ANY I/O device will steal some of that memory area for its own use. therefore, all the I/O devices reduce the total memory space avail. In your case, they take about a gig.
a b V Motherboard
October 20, 2008 7:40:32 PM

(Thanks to Scotteq for saving this answer on a file so others can post it when this qustion is asked at least once a week. To the mods: can we have a sticky about this using Scotteq's file as the main post?)

In 32 bit Windows operating systems, the total addressable space available is 4GB. If you installed total 4GB memory, the system will detect less than 4GB of total memory because of address space allocation for other critical functions, such as:

- System BIOS (including motherboard, add-on cards, etc..)
- Motherboards resources
- Memory mapped I/O
- Configuration for AGP/PCI-Ex/PCI
- Other memory allocations for PCI devices

Different onboard devices and different add-on cards (devices) will result of different total memory size. e.g. more PCI cards installed will require more memory resources, resulting of less memory free for other uses.

This limitation applies to most chipsets & Windows XP/Vista 32-bit version operating systems.

If you install a Windows operating system, if more than 3GB memory is required for your system, then the below conditions should be met:

1. The memory controller which supports memory swap functionality is used. The latest chipsets like Intel 975X, 955X, Nvidia NF4 SLI Intel Edition, Nvidia NF4 SLI X16, AMD K8 and newer architectures can support the memory swap function.

2. Windows XP Pro X64 Ed. (64-bit), Windows Vista 64, or other OS which can address more than 4GB memory.
October 20, 2008 7:46:07 PM

Nik_I said:
sounds like you're using a 32-bit version of windows. if that's the case, then you'll only be able to see at most 3.25GB of your ram regardless of how much you have. and subtract your video card's ram from that 3.25GB.


I know I'm nitpicking, but I really wish people would stop giving an exact figure for the 32-bit limit. There is NO exact figure. The amount of address space utilized by the system depends on the devices in use. I've seen up to 3.5 GB on a fairly decent workstation. it's more of a 2.75-3.5 GB range.

Also you do not subtract video memory UNLESS it uses Turbocache or something similar. Most decent video cards do not use that type of memory, integrated types (basic PC's, notebooks) tend to use it and be advertised as "up to XXX of video RAM".

a b V Motherboard
October 20, 2008 7:54:54 PM

Actually, you do subtract video memory regardless. I'm running Server 2K3 32-bit with a 9500GT and I'm showing only 3.12GB of RAM.
October 20, 2008 8:23:27 PM

As written in my first post, I'm running Debian.
I've the HIGHMEM kernel option on.

But, the point is not to be with the OS as inside the BIOS the motherboard tells that there is 1G used by system resources and at the boot it counts only 3G of ram.

Every effing OS will see only 3G of ram. Anybody has experienced this kind of pb on a supermicro motherboard ?
October 20, 2008 8:24:15 PM

BTW, I've installed VMWARE esx on it, and it only see 3G of ram (or this OS see 8G of ram on anothers machines with another motherboard)
October 20, 2008 8:24:54 PM

michiganteddybear said:
2 things here, as previously mentioned, 32 bit os will limit you to about 3 gig.

2nd.. your mobo supports a max of 4 gig. that means that ANY I/O device will steal some of that memory area for its own use. therefore, all the I/O devices reduce the total memory space avail. In your case, they take about a gig.

I'll have a look at it, but it seems to be huge !
a b } Memory
a b V Motherboard
October 20, 2008 10:16:12 PM

gootanoo said:
I've a supermicro server with a motherboard P8SC8. I recently upgraded form 1GB (2*512) to 4GB (4*1G : max supported memory on this platform refering the vendor website). Something strange occured :
There is nothing 'strange' about it. Your chipset is hard-limited to 32-bit physical addressing (i.e. 4GB RAM). Some of that must be reserved for hardware. The BIOS is nice enough to show you there is no "missing" RAM, it is being reserved for that hardware resource need. All RAM is present and accounted for in the BIOS.
Quote:
Actually, you do subtract video memory regardless.
You subtract shared UMA video memory regardless, but discrete frame buffer may not always be mapped 1:1 into system address space. Typically, graphics cards will map their memory using a 256MB or 512MB IOMMU device window. If that is equal to or less than the amount of RAM on the graphics card, great. Otherwise, its not going to be mapped 1:1.
October 21, 2008 7:26:52 AM

tcsenter said:
There is nothing 'strange' about it. Your chipset is hard-limited to 32-bit physical addressing (i.e. 4GB RAM). Some of that must be reserved for hardware. The BIOS is nice enough to show you there is no "missing" RAM, it is being reserved for that hardware resource need. All RAM is present and accounted for in the BIOS.
Quote:
Actually, you do subtract video memory regardless.
You subtract shared UMA video memory regardless, but discrete frame buffer may not always be mapped 1:1 into system address space. Typically, graphics cards will map their memory using a 256MB or 512MB IOMMU device window. If that is equal to or less than the amount of RAM on the graphics card, great. Otherwise, its not going to be mapped 1:1.

A friend of mine got an older version on this motherboard : the P4SC8. Supermicro's website tells it supports up to 4GB ram (like the P8SC8). My friend can use all of his 4GB ram on his OS. It's strange that a newer version can't do that.
October 21, 2008 9:03:58 AM

I've contacted supeemicro support :

Quote:

Hello Sir,



This is related to the Intel E7221 chipset

This chipset does not support Memory Remapping

See attached document for more information



Only solution is to use different mainboard with newer chipset


great. The motherboard support 4GB ram but you can use only 3GB...
a b } Memory
a b V Motherboard
October 21, 2008 9:51:16 AM

gootanoo said:
A friend of mine got an older version on this motherboard : the P4SC8. Supermicro's website tells it supports up to 4GB ram (like the P8SC8). My friend can use all of his 4GB ram on his OS. It's strange that a newer version can't do that.

Sorry, your friend is mistaken. The E7210 chipset used on the P4SC8 has the same hard limit as the E7221 used on the P8SC8: http://download.intel.com/support/motherboards/server/s...
October 30, 2008 12:38:54 AM

kamel5547 said:
I know I'm nitpicking, but I really wish people would stop giving an exact figure for the 32-bit limit. There is NO exact figure. The amount of address space utilized by the system depends on the devices in use. I've seen up to 3.5 GB on a fairly decent workstation. it's more of a 2.75-3.5 GB range.

Also you do not subtract video memory UNLESS it uses Turbocache or something similar. Most decent video cards do not use that type of memory, integrated types (basic PC's, notebooks) tend to use it and be advertised as "up to XXX of video RAM".


yeh, i'm seein 3.5GB on mine. Granted, Win32 can't see any more then 4.3GB total system RAM, but there's something to do with the motherboard that makes it even less then what you'd think sometimes.
!