Chassis Plans ATXP-875P, Техническое описание

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Chapter 3: Upgrading ATXP-875P – Technical Reference
40 Chassis Plans
Addressable Memory
The ATXP-875P utilizes 4 GB of addressable system memory. Typically the address space that is allocated for PCI
add-in cards, AGP aperture, BIOS (firmware hub), and chipset overhead resides above the top of DRAM (total
system memory). On a system that has 4 GB of system memory installed, it is not possible to use all of the installed
memory due to system address space being allocated for other system critical functions. These functions include the
following:
•
Memory-mapped I/O that is dynamically allocated for PCI and AGP cards.
•
AGP aperture.
•
APIC and chipset overhead (approximately 18 MB).
•
BIOS/firmware hub (approximately 2 MB).
The amount of installed memory that can be used will vary based on add-in cards and BIOS settings. For example, if
the PCI cards are requesting 200 MB of system memory and the AGP aperture is set to 256 MB in the BIOS Setup
program, there will be approximately 3.54 GB of memory that can be accessed. All installed system memory can be
used when there is no overlap of system addresses. For example, all of the system address space can be utilized on a
system that has 2 GB of installed system memory, AGP aperture set for 256 MB, and the PCI cards are requesting
200 MB of system address space.
NOTES
• When ECC DIMMs are used, the Power-On Self Test (POST) will take longer to complete.
• Remove the AGP video card before installing or upgrading memory to avoid interference with the memory
retention mechanism.
• To be fully compliant with all applicable DDR SDRAM memory specifications, the board should be
populated with DIMMs that support the Serial Presence Detect (SPD) data structure. This allows the BIOS
to read the SPD data and program the chipset to accurately configure memory settings for optimum
performance.
The following table lists the supported DDR DIMM Configurations:
Table 3-1 Supported DDR DIMM Configurations
Front Side Population Back Side Population DIMM
Capacity # of
Dev./
DIMM
# of
Sides DRAM
Tech.
Count Config Count Config
64 MB 8 SS 64 Mbit
8
8 M x 8
64 MB 4 SS 128 Mbit
4
8 M x 16
128 MB 16 DS 64 Mbit
8
8 M x 8
8 8 M x 8
128 MB 8 SS 128 Mbit
8
16 M x 8
128 MB 4 SS 256 Mbit
4
16 M x 16
256 MB 16 DS 128 Mbit
8
16 M x 8
8 16 M x 8
256 MB 8 SS 256 Mbit
8
32 M x 8
256 MB 4 SS 512 Mbit
4
32 M x 16
512 MB 16 DS 256 Mbit
8
32 M x 8
8 32 M x 8
512 MB 8 SS 512 Mbit
8
64 M x 8
1024 MB 16 DS 512 Mbit
8
64 M x 8
8 64 M x 8