82845MP Datasheet, PDF (108/157 Pages) Intel Corporation – Intel 845 Family Chipset-Mobile 82845MP/82845MZ Chipset Memory Controller Hub Mobile (MCH-M)

Intel^®82845MP/82845MZ Chipset-Mobile (MCH-M)
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4.1.3. ISA Hole Memory Space
BIOS software may optionally open a “window” between 15 MB and 16 MB (0_00F0_0000h to
0_00FF_FFFF) that relays transactions to hub interface instead of completing them with a system
memory access. This window is opened with the FDHC.HEN configuration field.
Figure 7. Detailed Extended Memory Range Address Map
High BIOS, optional
extended SMRAM
Local Apic Space
Hub interface_D-E I/O
Apic Space
Hub interface_A I/O
Apic Space
Extended SMRAM
Space
Extended SMRAM
(translated to < 1MB)
ISA Hole
1_0000_0000 (4GB)
Key
FF00_0000
=
FEF0_0000
FEE0_0000
=
FED0_0000
=
FEC8_0000
FEC0_0000
=
Top of Low Memory (TOM)
TEM - TSEG
100C_0000
100A_0000
0100_0000 (16 MB)
00F0_0000 (15 MB)
Hub interface_A (always)
Region allowed for AGP/PCI
DRAM Region
Optional DRAM Region
0010_0000 (1MB)
4.1.4. TSEG SMM Memory Space
TSEGSMM
From
TOM – TSEG
To
TOM
The TSEG SMM space allows system management software to partition a region of main memory just
below the top of low memory (TOM) that is accessible only by system management software. This
region may be 128 kB, 256 kB, 512 kB, or 1 MB in size, depending upon the ESMRAMC.TSEG_SZ
field. SMM memory is globally enabled by SMRAM.G_SMRARE. Requests may access SMM system
memory when either SMM space is open (SMRAM.D_OPEN) or the MCH-M receives an SMM code
request on its system bus. In order to access the TSEG SMM space, the TSEG must be enabled by
ESMRAMC.T_EN. When all of these conditions are met, then a system bus access to the TSEG space
(between TOM-TSEG and TOM) is sent to system memory. If the high SMRAM is not enabled or if the
TSEG is not enabled, then all memory requests from all interfaces are forwarded to system memory. If
the TSEG SMM space is enabled, and an agent attempts a non-SMM access to TSEG space, then the
transaction is specially terminated.
Hub interface and AGP originated accesses are not allowed to SMM space.
108
Datasheet
250687-002