Avago Technologies LSI53C1010 - Manual (Page 238)

10-2 Multithreaded I/O
Figure 10.1 Multithreaded System Operation
Multithreaded algorithms are similar to single threaded algorithms with
disconnects, but a new element called the scheduler is added. The
scheduler keeps track of SCSI bus operations when more than one task
is active at a time. The SCRIPTS code must be stored in RAM to allow
multithreaded operation because SCRIPTS and the CPU dynamically
modify SCRIPTS. A multithreaded SCRIPTS algorithm contains three
parts: the main SCRIPTS, the scheduler SCRIPTS, and the reselect
SCRIPTS. These areas are described in detail after the overview of
multithreaded I/O below. This example shows how to implement a
scheduler in SCRIPTS. This is only one method of implementing a
scheduler. You can choose to schedule I/Os in an upper layer, such as
in the “C” driver code.
10.2 Multithreaded Operations Flow
Figure 10.2 shows the flow during multithreaded operation. The heavy
lines in the figure represent the initial flow of information for a new
operation. The lighter weight lines represent the flow as the chip finishes
pending steps of a multithreaded operation.
Task 1
Operating System
Task 2 Task 3
SCRIPTS
Device Driver
SCSI Bus
Processor
Disk 1
Disk 2
Disk 3