Dclkin Routing And Loading Requirements - Intel i960 Design Manual

DCLKOUT and the clock buffer outputs may be between 1 and 8 inches. Each of the four clock
buffer outputs must be equal in length. Refer to
capacitance requirements. DCLKIN requires an external capacitor to match the loading seen on
the other clock buffer outputs. Traces from the processor to the capacitor must be within 0.5
inches. The DCLKIN trace length must be equal to the clock buffer output trace length plus the
additional length specified in
Table 4-5.

DCLKIN Routing and Loading Requirements

Memory Configuration
168-pin SDRAM DIMM
144-pin SO-DIMM
Two discrete SDRAM devices
Four discrete SDRAM devices
Eight discrete SDRAM devices
Nine discrete SDRAM devices
Note: The 66 MHz Unbuffered 168-Pin SDRAM DIMM requires four clock inputs. The lumped
capacitance value required on DCLKIN is 18 pf in this reference design.
Design Guide
®
Intel 80960RM/RN Processor Memory Subsystem
Table 4-5
Table 4-5.
Additional DCLKIN Trace Length
4.5 +/- 0.1 inches
3.4 +/- 0.1 inches
1.3 +/- 0.1 inches
4.5 +/- 0.1 inches
4.5 +/- 0.1 inches
4.5 +/- 0.1 inches
*
Intel® i960® RM/RN I/O Processor
for the DCLKIN trace length and
DCLKIN Capacitance
18 pF
8.2 pF
3.3 pF
12 pF
12 pF
18 pF
21