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Register Description
R
94 Intel
®
82845 MCH for SDR Datasheet
3.6.23 DWTC—DRAM Write Thermal Management Control
Register (Device 1)
Address Offset: 50–57h
Default Value: 00h
Access: R/W/L
Size: 64 bits
Bit Descriptions
63:41 Reserved.
40:28 Global Write Hexword Threshold (GWHT). The 13-bit value in this field is multiplied by 2
15
to
arrive at the number of hexwords that must be written within the Global DRAM Write Sampling
Window to cause the thermal management mechanism to be invoked.
27:22 Write Thermal Management Time (WTMT). This value provides a multiplier between 0 and 63
that specifies how long thermal management remains in effect as a number of Global DRAM
Write Sampling Windows. For example, if GDWSW is programmed to
1000_0000b and WTT is set to 01_0000b, then thermal management will be performed for
8192*10
5
host clocks (@ 100 MHz) seconds once invoked (128 * 4*10
5
host clocks * 16).
21:15 Write Thermal Management Monitoring Window (WTMMW). The value in this register is
padded with four 0s to specify a window of 0–2047 host clocks with a 16-clock granularity.
While the thermal management mechanism is invoked, system memory writes are monitored
during this window. If the number of hexwords written during the window reaches the Write
Thermal Management Hexword Maximum (bits 14:3), then write requests are blocked for the
remainder of the window.
14:3 Write Thermal Management Hexword Maximum (WTMHM). The Write Thermal
Management Hexword Maximum defines the maximum number of hexwords between 0–4095
that are permitted to be written to system memory within one Write Thermal Management
Monitoring Window.
2:1 Write Thermal Management Mode (WTMMode).
00 = Thermal management via Counters and Hardware Thermal Management_on signal
mechanisms disabled.
01 = Hardware Thermal Management_on signal mechanism is enabled. In this mode, as long
as the Thermal Management_on signal is asserted, write thermal management is in effect
based on the settings in WTMW and WTHM. When the Thermal Management_on signal is
deasserted, write thermal management stops and the counters associated with the
WTMW and WTHM are reset. When the hardware Thermal Management_on signal
mechanism is not enabled, the Thermal Management_on signal has no effects.
10 = Counter mechanism controlled through GDWSW and GWHT is enabled. When the
threshold set in GDWSW and GWHT is reached, thermal management start/stop cycles
occur based on the settings in WTT, WTMW and WTHM.
11 = Reserved.
0 START Write Thermal Management (SWTM). Software writes to this bit to start and stop write
thermal management.
0 = Write thermal management stops and the counters associated with WTMW and WTHM are
reset.
1 = Write thermal management begins based on the settings in WTMW and WTHM, and
remains in effect until this bit is reset to 0.
0 Reserved.