MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
9-1
Chapter 9
Instruction Execution Timing
This chapter describes the timing of instructions that execute in the core. Examples show stalls and bubbles
due to serialization, latency, and blockage.
9.1
Instruction Execution Timing Examples
The following sections provide timings for the following scenarios:
•
Data cache load
•
Writeback arbitration
•
Private writeback bus load
•
Fastest external load (data cache miss)
•
Full completion queue (CQ)
•
Branch instruction handling
•
Branch prediction
All examples assume an instruction cache hit.
9.1.1
Data Cache Load with a Data Dependency
Figure 9-1
shows a data cache load with zero wait states. The sub instruction depends on the value loaded
to r12,which causes a bubble in the instruction stream. The example in
Section 9.1.3, “Private Writeback
Bus Load,”
has no such dependency.
lwz r12,64
(SP)
sub r3,r12,3
addic r4,r14,1
mulli r5,r3,3
addi r4,3(r0)
Figure 9-1. Data Cache Load Timing
lwz
sub
mulli
addi
addic
Fetch
Decode
Read + Execute
Writeback
L Address Drive
L Data
Load Write Back
lwz
sub
Bubble
addic
lwz
sub
sub
addic
ld
ld
ld
GCLK1
addic
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...