The Pentium Pro

Pentium Pro

Pentium Pro is a pure RISC processor. It is optimized for 32 bit processing in Windows NT or
OS/2. It is unique in that the L2 cache is built-in. This is like two chips in one.
Pentium Pro development started in 1991, in Oregon. It was introduced in late 1995. The new
features were:
  • Built in optimized L2 cache with 256 KB or 512 KB. This is connected to the CPU itself
  • with a 64 bit back side bus. Thus, the L2 cache runs synchronous with the CPU speed.
  • Multiple branch prediction, where the CPU anticipates the next instruction. Data Flow
  • Analysis, which should reduce data dependence. Speculative Execution, where the CPU attempts to anticipate instruction results.
  • 5.5 million transistors in the CPU, 15 million for the 256 KB SRAM L2 cache. (6 transistors per bit).
  • 4 pipelines for simultaneous instruction execution.
  • RISC instructions with concurrent x86 CISC code to MicroOps RISC instructions
  • decoding.

  • 2.9 Volt 4 layer BiCMOS processor technology.
  • Patented protocol. Thus, other CPU manufacturers cannot use the Pentium Pro socket
    and chip set. This is not to the users advantage.

Here you see a rectangular chip. The CPU and L2 cache are separate units inside this chip

Pentium Pro is primarily optimized to 32 bit program execution. Since I use a PPro 200 MHZ
(which runs at 233 MHZ) and experience tremendous power in my Windows 95 environment, I can recommend it for ordinary use.

Pentium Pro is especially designed for Windows NT and other genuine 32 bit environments.
Since the introduction of Pentium II, the price on PPro has dropped and soon it will be out of

Pentium II

Pentium Pro "Klamath" was the code name for Intel's new top processor. It is a partially
reduced and partially improved Pentium Pro model. The construction of Pentium II is interesting but also controversial.
  • With MMX instructions
  • Improved 16 bit program execution (joy for Windows 3.11 users)
  • Doubled and improved L1 cache (16 KB + 16 KB) CPU is mounted together with 512 KB L2 on a cartridge connected to the main board using the slot one connector.
  • New increased internal speed: from 233 MHZ to 333 MHZ
The most interesting change is the separation of CPU and L2 cache. Intel found it too costly to
combine them in one chip as in Pentium Pro. To facilitate mass production, cache RAM of a
different brand (Toshiba) was used. The cache RAM is marked 7 ns allowing a clockfrequency
of maximum 150 MHZ.

Pentium II is a large rectangular plastic box, which contains the CPU and cache. There is also
a small controller (S82459AB) and a well dimensioned cooling fan. All are mounted on a card.
This card with chips weighs about 380 g (13 ounces). It fits in a new 242 pin Single Edge
Connector on the system board.
Here you see the SEC-module:

With the new design, the L2 cache has its own bus. It runs at half the CPU speed, like 133
MHZ. This is clearly a retrogression from the Pentium Pro, which can run at 200 MHZ betweenthe CPU and L2 cache. It is countered by the improved L1 cache, which really zips along! Here you see a comparison:

Pentium II is Intel's top model. It is currently available in 233, 266, 300, 333, 350 and 400 MHZ editions. With the new 82440LX and 82440BX chip sets Pentium II is an excellent performer. Read on for more information. But first the rival:

AMD K6-II or K6-3D

The newest version of the K6 code name "Chomper" is an intriguing new CPU. The K6 model 8 is called K6-2, and it is manufactured with 0.25 micron technology. This gives the front side bus (system bus) a speed of 100 MHz.
The K6-2 also holds a new 3D plug-in (called 3DNow!) for better game performance. It is 21
new instructions that can be used by software developers giving a better 3D-performance. To
benefit from it, you need a graphics driver ore a came, which deals directly with the new
commands. 3DNow! is not compatible with MMX.

The next version of this chip - model 9 code name "Sharptooth" - will incorporate three levels of cache! In the CPU you find both a L1- and a L2-cache. The in-chip L2 cache of 64 KB runs at processor speed. On the main board you will find L3-cache up to 1 megabyte!


On January the 26th Intel introduced the new 333 MHZ model of Pentium II. It is the first of a
second generation Pentium-II's known under the code name "Deschutes". The chips are
produced with 0.25 micron technology, which reduces the power consumption with more than
50 % compared to the original Pentium II "Klamath" with its 0.35 micron technology. The core
voltage is down from 2.8 to 2.0 Volt.

On April the 15th Intel released the next line of Deschutes. The system bus is sped up to 100
MHz. This will internally be multiplied by the clock factors 3.5, 4.0 and (June 1998) 4.5, making the CPU running at 350, 400 and 450 MHz. These CPU's uses the new chip set: 82440BX.
So the Deschutes chips use two different mother boards:
  • LX-based for the 333 MHZ version (5 X 66 MHZ)
  • BX-based for the 350 and 400 MHZ versions (3.5 and 4.0 X 100 MHZ).
The L2 cache RAM has to deal with these higher clock frequencies:

Also the cache RAM chips are cooled on the new cartridges.

The Celeron, a Pentium II-SX

Intel is having a hard time with the Pentium II which is to expensive. Most users buy the AMD
K6-233, which offers very good performance at a moderate price.
Thus Intel has created a brand new CPU called Celeron. It is a Pentium II cartridge except from the L2-cache, which has been chopped away. It uses a new Covington core, and we could just as well call it a Pentium II-SX. Later this year Intel replaces their Pentium MMX with the Celerons.