User Guide

190 Hardware Reference Manual
Intel
®
IXP2800 Network Processor
DRAM
5.4 Bank Policy
The RDRAM Controller uses a “closed bank” policy. Banks are activated long enough to do an
access and then closed and precharged. They are not left open in anticipation of another access to
the same page. This is unlike many CPU applications, where there is a high degree of locality.
Since that locality does not exist in the typical applications in which the IXP2800 Network
Processor uses RDRAM, the “closed bank” policy is used.
Figure 67. IXP2800 Clocking for RDRAM at 400 MHz
A9727-01
RMC RAC
100 MHz
50 MHz
25
MHz
25
MHz
Bus CLK = 400 MHz
System
Ref_Clk
DRCG
PLL
/4
/4/2
PCLK =
100 MHz
CLK_PHASE_REF
Phase Detector
SYNCLK =
100 MHz
/4
x 8
Figure 68. IXP2800 Clocking for RDRAM at 508 MHz
A9728-01
RMC RAC
100 MHz
63.5 MHz
31.75
MHz
31.75
MHz
Bus CLK = 508 MHz
System
Ref_Clk
DRCG
PLL
/4
/4/2
PCLK =
127 MHz
CLK_PHASE_REF
Phase Detector
SYNCLK =
127 MHz
/4
x 8