AMD AMD5K86 - Page 99

AMD~
AMD5J1l6 Processor Technical Reference Manual
18524BjO-Mar1996
4-6
The second column contains an identifier with the following
format:
ilL. MODrm[2:0]
L MODrm[5:3]
Opcode
'-------- Addressing Mode:
Ox = register
10 = memory without index
Ix = memory with or without index
11 = memory with index
'--------- 1 = two-byte opcode (OF xx)
The third column in the tables indicates whether the instruc-
tion is Fastpath (F) or Microcoded (M). Fastpath and MROM
ROPs cannot both be present in a decode stage at the same
time. If a microcoded instruction appears at the head of the
byte queue without having been present in the queue on the
previous cycle, there is a one-cycle penalty for MROM entry
point generation.
Each x86 instruction is converted into one or more ROPs. The
fourth column shows the execution unit and timing for each of
the ROPs. The ROP types and corresponding execution units
are:
• ld-Ioad/store
• st-Ioad/store
• alu-either aluO or alul
• aluO-aluO only
• alul-alul only
• brn- branch
• Jadd-floating-point add pipe
• jmul-floating-point multiply pipe
• fpmv-floating-point move and compare pipe
• fpJill-floating-point upper half
Performance