Datasheet 33
Electrical Specifications
2.7.3 Phase Lock Loop (PLL) and Filter
VCCA and VCCIOPLL are power sources required by the PLL clock generators for the Pentium D
processor. Since these PLLs are analog in nature, they require quiet power supplies for minimum
jitter. Jitter is detrimental to the system: it degrades external I/O timings as well as internal core
timings (i.e., maximum frequency). To prevent this degradation, these supplies must be low pass
filtered from VTT.
The AC low-pass requirements, with input at VTT are as follows:
•< 0.2 dB gain in pass band
•< 0.5 dB attenuation in pass band < 1 Hz
•> 34 dB attenuation from 1 MHz to 66 MHz
•> 28 dB attenuation from 66 MHz to core frequency
The filter requirements are illustrated in Figure 2-4.
Table 2-18. BSEL[2:0] Frequency Table for BCLK[1:0]
BSEL2 BSEL1 BSEL0 FSBFrequency
L L L RESERVED
L L H 133MHz
L H H RESERVED
L H L 200MHz
H L L RESERVED
H L H RESERVED
H H H RESERVED
H H L RESERVED