
2-5
PENTIUM® PRO PROCESSOR ARCHITECTURE OVERVIEW
The ICache is a local instruction cache. The Next_IP unit provides the ICache index, based on
inputs from the Branch Target Buffer (BTB), trap/interrupt status, and branch-misprediction in-
dications from the integer execution section.
The ICache fetches the cache line corresponding to the index from the Next_IP, and the next line,
and presents 16 aligned bytes to the decoder. The prefetched bytes are rotated so that they are
justified for the instruction decoders (ID). The beginning and end of the IA instructions are
marked.
Three parallel decoders accept this stream of marked bytes, and proceed to find and decode the
IA instructions contained therein. The decoder converts the IA instructions into triadic µops (two
logical sources, one logical destination per µop). Most IA instructions are converted directly into
single µops, some instructions are decoded into one-to-four µops and the complex instructions
require microcode (the box labeled MIS in Figure 2-4). This microcode is just a set of prepro-
grammed sequences of normal µops. The µops are queued, and sent to the Register Alias Table
(RAT) unit, where the logical IA-based register references are converted into Pentium Pro pro-
cessor physical register references, and to the Allocator stage, which adds status information to
the µops and enters them into the instruction pool. The instruction pool is implemented as an
array of Content Addressable Memory called the ReOrder Buffer (ROB).
This is the end of the in-order pipe.
2.2.2.
The Dispatch/Execute Unit
The dispatch unit selects µops from the instruction pool depending upon their status. If the status
indicates that a µop has all of its operands then the dispatch unit checks to see if the execution
resource needed by that µop is also available. If both are true, the Reservation Station removes
that µop and sends it to the resource where it is executed. The results of the µop are later returned
to the pool. There are five ports on the Reservation Station, and the multiple resources are
accessed as shown in Figure 2-5.
Содержание Pentium Pro Family
Страница 17: ...1 Component Introduction ...
Страница 26: ...2 Pentium Pro Processor Architecture Overview ...
Страница 27: ......
Страница 36: ...3 Bus Overview ...
Страница 62: ...4 Bus Protocol ...
Страница 105: ...5 Bus Transactions and Operations ...
Страница 126: ...6 Range Registers ...
Страница 131: ...7 Cache Protocol ...
Страница 135: ...8 Data Integrity ...
Страница 148: ...9 Configuration ...
Страница 161: ...10 Pentium Pro Processor Test Access Port TAP ...
Страница 172: ...11 Electrical Specifications ...
Страница 201: ...12 GTL Interface Specification ...
Страница 229: ...13 3 3V Tolerant Signal Quality Specifications ...
Страница 233: ...14 Thermal Specifications ...
Страница 239: ...15 Mechanical Specifications ...
Страница 241: ...15 2 MECHANICAL SPECIFICATIONS s Figure 15 1 Package Dimensions Bottom View ...
Страница 252: ...16 Tools ...
Страница 260: ...16 8 TOOLS Figure 16 4 Generic MP System Layout for Debug Port Connection ...
Страница 264: ...17 OverDrive Processor Socket Specification ...
Страница 290: ...A Signals Reference ...
Страница 320: ...Index ...
Страница 328: ......