MC68030 Datasheet, PDF (486/602 Pages) Motorola, Inc – ENHANCED 32-BIT MICROPROCESSOR

Instruction Execution Timing
11.6.18 Save and Restore Operations
The save and restore operation table indicates the number of clock periods needed for the
processor to perform the specified state save or to return from exception, with complete
execution times and stack length given. No additional tables are needed to calculate total
effective execution time for these operations. For instruction-cache case and for no-cache
case, the total number of clock cycles is outside the parentheses. The number of read,
prefetch, and write cycles is given inside the parentheses as (r/p/w). The read, prefetch, and
write cycles are included in the total clock cycle number.
All timing data ssumes two-clock reads and writes.
Operation
Bus Cycle Fault (Short)
Bus Cycle Fault (Long)
RTE (Normal Four Word)
RTE (Six Word)
RTE (Throwaway)
RTE (Coprocessor)
RTE (Short Fault)
RTE (Long Fault)
Head
0
0
1
1
1
1
1
1
Tail
I-Cache Case
No-Cache
Case
0
36(1/0/10)
38(1/2/10)
0
62(1/0/24)
64(1/2/24)
0
18(4/0/0)
20(4/2/0)
0
18(4/0/0)
20(4/2/0)
0
12(4/0/0)
12(4/0/0)
0
26(7/0/0)
26(7/2/0)
0
36(10/0/0)
26(10/2/0)
0
76(25/0/0)
76(25/2/0)
11.7 ADDRESS TRANSLATION TREE SEARCH TIMING
The time required for a search of the address translation tree depends on the configuration
of the tree structure and the descriptors in the tree, the states of the used (U) and modified
(M) bits in the descriptors, bus cycle time, and other factors. The large number of variables
involved implies that search time can best be calculated by a program. To determine the
time required for the MC68030 to perform the table search for a specific configuration, the
following interactive program can be used. It is a shell script suitable for use with sh(1) on
either UNIX^® System V or BSD 4.2. To use the program, run the script and answer the
questions about the system configuration and current state. The values shown in square
brackets at the ends of the question lines are the default values that the program uses when
carriage returns are entered.
The shell script assumes that the data bus between the MC68030 and memory is 32 bits
wide. To calculate the search time for a narrower bus, enter the appropriate multiple of the
bus cycle time in response to the bus cycle time prompt. Use the time required for two bus
cycles in the case of a 16-bit data bus. Use the time required for four bus cycles in the case
of an 8-bit data bus.
UNIX is a registered trademark of AT&T Bell Laboratories.
MOTOROLA
MC68030 USER’S MANUAL
11-51