82443BX Datasheet, PDF (72/132 Pages) Intel Corporation – Host Bridge/Controller

Register Description
3.3.40
DRTC—DRAM Read Thermal Throttling Control Register
(Device 0)
Offset:
Default:
Access:
Size:
E8h–EFh
0000_0000_0000_0000h
Read/Write/Lock
64 Bits
The contents of this register are protected by making the bits read-only once a ‘1’ is written to the
Throttle Lock bit (bit 63 of configuration register E0–E7h)
Bits
63:46
45:38
37:26
25:20
19:13
12:3
2:0
Description
Reserved
Global DRAM Read Sampling Window (GDRSW). This 8-bit value is multiplied by 4 to define
the length of time in milliseconds (0–1020) over which the number of QWords read from DRAM is
counted.
Global Read QWord Threshold (GRQT). The 12-bit value held in this field is multiplied by 215 to
arrive at the number of QWords that must be written within the Global DRAM Read Sampling
Window in order to cause the thermal throttling mechanism to be invoked.
Read Throttle Time (RTT). This value provides a multiplier between 0 and 63 which specifies
how long read thermal throttling remains in effect as a number of Global DRAM Read Sampling
Windows. For example, if GDRSW is programmed to 1000_0000b and RTT is set to 01_0000b,
then read thermal throttling will be performed for ~2 seconds once invoked (128 ms * 16).
Read Throttle Monitoring Window (RTMW). The value in this register is padded with 4 0’s to
specify a window of 0–2047 DRAM CLKs with 16 clock granularity. While the thermal throttling
mechanism is invoked, DRAM reads are monitored during this window—if the number of QWords
read during the window reaches the Throttle QWord Maximum, then Host and PCI read requests,
as well as all AGP requests, are blocked for the remainder of the window.
Read Throttle QWord Maximum (RTQM). The Read Throttle QWord Maximum defines the
maximum number of QWords between 0–1023 which are permitted to be read from DRAM within
one Read Throttle Monitoring Window while thermal throttling mechanism is in effect.
DRAM Read Throttle Mode. Normal DRAM read monitoring and thermal throttling operation are
enabled when bits 2:0 are set to 100. All other combinations are Intel Reserved.
000-011 = Intel Reserved
100 = Normal Operations
101-111 = Intel Reserved
3-46
82443BX Host Bridge Datasheet