CPU Interface Functional Overview
CPU Bus Multiple Masters
Copyright © 2002 Marvell
CONFIDENTIAL
Doc. No. MV-S300165-00, Rev. A
May 21, 2002, Preliminary
Document Classification: Proprietary Information
Page 29
Clock Synchronization
In a Symmetric Multiprocessor (SMP) system, the operating system needs the ability to synchronize the clocks on
all the processors. To do this, the operating system must also have the ability to stop all clocks at the same time.
The TBEN pin provided on the PowerPC CPUs can be used to implement this clock control function.
Instead of using a dedicated pin for this purpose, the GT-64260A uses an MPP pin to enable this synchronization.
The MPP must be configured to function as a general purpose output and must be connected to all of the CPUs’
TBEN pin.
Note
For more information, see
Section 8. "Multi-Purpose Pin Interface Functional Overview" on page 74
the corresponding section in the GT-64260A datasheet.
Inter-processor Communication
The processors communicate with each other through inter-processor interrupts (IPIs). IPIs can effectively sched-
ule and control threads over multiple processors.
The GT-64260A supports one dedicated interrupt output pin to the CPU (Interrupt*). When using more than one
CPU, the PCI0/1 interrupt or MPP output pins can be connected to the CPUs.
Note
When using the MPP interrupts (Int*[3:0]), the interrupt cause can be driven by only one interrupt cause
register - main interrupt cause register Low (offset 0xC18) or main interrupt cause register High (offset
Section 11. "Interrupt Controller Functional Overview" on page 82
or the GT-64260A
datasheet’s "Interrupt Controller" section.
The IPI is implemented by using the MPP interface in loops (CPU0 to CPU1, CPU1 to CPU0 etc.).
describes the interrupt pins connectivity in SMP systems with a single GT-64260A and two CPUs.