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308 Software Developer’s Manual
Register Descriptions
13.4.29 Receive Descriptor Tail
RDT (02818h;R/W)
This register contains the tail pointers for the receive descriptor buffer. The register points to a 16-
byte datum. Software writes the tail register to add receive descriptors to the hardware free list for
the ring.
Table 13-74. RDT Register Bit Description
13.4.30 Receive Delay Timer Register
RDTR (02820h; R/W)
This register is used to delay interrupt notification for the receive descriptor ring. Delaying
interrupt notification helps maximize the number of receive packets serviced by a single interrupt.
Warning: It is strongly recommended that the Delay Timer field of this register not be used. For any
application requiring an interrupt moderation mechanism, it is recommended that the Interrupt
Throttling Register (ITR) be used instead. ITR provides a more direct interrupt solution than
RDTR. In addition, Intel software device drivers use ITR instead of RDTR. Refer to the
82546EB
Gigabit Ethernet Controller Specification Update or 82546GB Gigabit Ethernet Controller
Specification Update
for additional details.
Table 13-75. RDTR Register Bit Description
31 16 15 0
Reserved RDT
Field Bit(s)
Initial
Value
Description
RDT 15:0 0b Receive Descriptor Tail.
Reserved 31:16 0b
Reserved
Reads as 0b.
Should be written with 0b for future compatibility.
31 30 16 15 0
FPD Reserved Delay Timer
Field Bit(s)
Initial
Value
Description
Delay Timer 15:0 0b Receive delay timer measured in increments of 1.024 s.
Reserved 30:16 0b Reserved. Reads as 0b.
FPD 31 0b
Flush partial descriptor block when set to 1b; ignore otherwise.
Reads 0b (self-clearing).