RG82845M Intel, RG82845M Datasheet - Page 79

• Manufacturer Part Number: RG82845M
• Description: Chipset Memory Controller Hub Mobile
• Manufacturer: Intel

3.7.33.
250687-002
R
Address Offset:
TOM – Top of Low Memory Register – Device #0
Default Value:
Access:
Size:
This register contains the maximum address below 4 GB that should be treated as a memory access. Note
that this register must be set to a value of 0100h (16 MB) or greater. Usually it will sit below the areas
configured for the hub interface, PCI memory, and the graphics aperture.
15:4
3:0
Bit
Top of Low Memory (TOM): This register contains the address that corresponds to bits 31 to 20 of
the maximum DRAM memory address that lies below 4 GB. Configuration software should set this
value to either the maximum amount of memory in the system or to the minimum address allocated
for PCI memory or the graphics aperture, whichever is smaller.
Programming example: 400h = 1 GB. An access to 4000_0000h or above will be considered above
the TOM and therefore not routed to DRAM. It may go to AGP, aperture, or subtractively decode to
Hub Interface.
Reserved
C4-C5h
0100h
Read/Write
16 bits
Datasheet
Intel
®
Description
82845MP/82845MZ Chipset-Mobile (MCH-M)
79