
4
SCD7000A Rev C 9/9/09
Aeroflex Plainview
Figure 2 is a simplification of the pipeline section and
illustrates the basics of the instruction issue mechanism.
The figure illustrates that one F pipe instruction and one
M pipe instruction can be issued concurrently but that two
M pipe or two F pipe instructions cannot be issued. Table 2
specifies more completely the instructions within each
class.
.
The
symmetric
superscalar
capability
of
the
ACT 7000ASC, in combination with its low latency integer
execution units and high-throughput fully pipelined
floating-point
execution
unit,
provides
unparalleled
price/performance in computational intensive embedded
applications.
Pipeline
The logical length of both the F and M pipelines is five
stages with state committing in the register write, or W,
pipe stage. The physical length of the floating-point
execution pipeline is actually seven stages but this is
completely transparent to the user.
Figure 3 shows instruction execution within the
ACT 7000ASC
when
instructions
are
issuing
simultaneously down both pipelines. As illustrated in the
figure,
up
to
ten
instructions
can
be
executing
simultaneously. This figure presents a somewhat simplistic
Figure 2 – Instruction Issue Paradigm
FP
F Pipe
F Pipe IBus
M Pipe IBus
FP
M Pipe
Integer
F Pipe
Integer
M Pipe
Dispatch
Unit
Instruction
Cache
Table 2 – Dual Issue Instruction Classes
integer
load/store
floating-point
branch
add, sub, or,
xor, shift, etc.
lw, sw, ld, sd,
ldc1, sdc1,
mov, movc,
fmov, etc.
fadd, fsub,
fmult, fmadd,
fdiv, fcmp,
fsqrt, etc.
beq, bne,
bCzT, bCzF,
j, etc.
I0
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
I1
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
I2
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
I3
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
I4
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
I5
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
I6
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
I7
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
I8
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
I9
1l
2l
1R
2R
1A
2A
1D
2D
1W
2W
one cycle
1I-1R:
2I:
2R:
1A:
1A-2A:
2A:
2A-2D:
1D:
2W:
Instruction cache access
Instruction virtual to physical address translation
Register file read, Bypass calculation, Instruction decode, Branch address calculation
Issue or slip decision, Branch decision
Data virtual address calculation
Integer add, logical, shift
Store Align
Data cache access and load align
Data virtual to physical address translation
Register file write
Figure 3 – Pipeline