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Register Description
R
64 Intel
®
82845 MCH for SDR Datasheet
3.5.24 ESMRAMC—Extended System Mgmt RAM Control Register
(Device 0)
Address Offset: 9Eh
Default Value: 38h
Access: RO, R/W, R/WC, R/W/L
Size: 8 bits
The Extended SMRAM register controls the configuration of Extended SMRAM space. The
Extended SMRAM (E_SMRAM) memory provides a write-back cacheable SMRAM memory
space that is above 1 MB.
Bit Description
7 H_SMRAM_EN (H_SMRAME)—R/W/L. Controls the SMM memory space location (i.e., above 1
MB or below 1 MB). When G_SMRAME is 1 and H_SMRAME this bit is set to 1, the high
SMRAM memory space is enabled. SMRAM accesses from FEDA_0000h to FEDB_FFFFh are
remapped to DRAM address 000A0000h to 000BFFFFh.
Once D_LCK is set, this bit becomes read only.
6 E_SMRAM_ERR (E_SMERR)—R/WC.
0 = The software must write a 1 to this bit to clear it.
1 = This bit is set when host accesses the defined memory ranges in Extended SMRAM (High
Memory and T-segment) while not in SMM space and with the D-OPEN bit = 0.
5 SMRAM_Cache (SM_CACHE)—RO. Hardwired to 1.
4 SMRAM_L1_EN (SM_L1)—RO. Hardwired to 1.
3 SMRAM_L2_EN (SM_L2)—RO. Hardwired to 1.
2:1 TSEG_SZ[1-0] (T_SZ)—R/W. Selects the size of the TSEG memory block if enabled. This
memory is taken from the top of system memory space (i.e., TOM – TSEG_SZ), which is no
longer claimed by the memory controller (all accesses to this space are sent to the hub interface
if TSEG_EN is set). This field decodes as follows:
00 = (TOM–128 KB) to TOM
01 = (TOM–256 KB) to TOM
10 = (TOM–512 KB) to TOM
11 = (TOM–1 MB) to TOM
Once D_LCK is set, this bit becomes read only.
0 TSEG_EN (T_EN)—R/W/L. Enabling of SMRAM memory (TSEG, 128 KB, 256 KB, 512 KB or
1 MB of additional SMRAM memory) for Extended SMRAM space only. When G_SMRAME =1
and TSEG_EN = 1, the TSEG is enabled to appear in the appropriate physical address space.
Once D_LCK is set, this bit becomes read only.