• Intel Processors
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• Quality and other marks on the Intel Pentium Processors
• Intel CPU Markings FAQ
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The PCI Bus Clock is always half of the external CPU Clock speed (e.g. a P166 will have a PCI Bus Clock of 33 MHz) EISA & ISA Systems have at most a 8MHz Bus Clock (4.77MHz minimum).

3V is in reality 3.3V, however, it is usually simplified with a 3V specification.

All Overdrive (OD) Processors are direct chip replacements and require no modifiaction of the switch or jumper settings on the motherboard.

Generally speaking you can use a faster CPU w/ a slower clock speed (MHz), but you will not take full advantage of the processors speed capabilities.

Generally speaking a CPU made in the Philippines w/ a SSS mark after the Step No is considered the best quality obtainable from Intel, however Intels practices make it virtually impossible to predict what grade of CPU's you receive, when the order is placed w/ Intel.
For most desktop PC's it is unimportant what grade of CPU is used, as the powersupply and Chip set tolerances are defined close enough in order to work w/ all CPU's and a second CPU can not be installed anyways. A 90MHz CPU or faster w/ a i75 embossing are most likely fake, and should be reported to Intel, identifying the source if known.

Intel Pentium 200 MHz top view
Intel Pentium 200 MHz bottom view

Intel Pentium Pro 200 MHz top view
Intel Pentium Pro 200 MHz bottom view

What do the markings on the top and bottom of my processor mean?

Answer:

The family of the processor is always there on top, along with the product code and frequency. For example, A80502-90 means a 90 MHz version of the Pentium processor, model 2.

Three-digit numbers following SX/SK/SU/SY/SZ are known as the s-spec numbers, and identify any specific characteristics that the part has, including the stepping, or version number. S-spec numbers are always printed on top of the package and are also on he bottom for newer versions of the Pentium processor. These SX numbers have nothing to do with previous products that we've had such as the Intel486 SX processor.

M C '92 '93 or M C '92 '95 are printed on the top and/or bottom. These dates give copyright information. They are not related to the date of manufacture of any product.

I have heard that I can read the voltage specification directly from the package.

Answer:

Yes, for newer Pentium processors this is true. If a processor package has this information, it will be on the bottomside following the s-spec marking. The notation will be a slash mark followed by ABC, such as: SK110 / ABC

Here is the decoding of ABC:

I would like to know what voltage range my Pentium® processor requires. How do I determine this?

Answer:

If your processor does not have the voltage markings directly on the package (see above), use the s-spec number to determine this. The s-spec is a 3-digit number on the processor package which follows SX, SK, SU, SY, or SZ.

Use the s-specs shown in the following table to find the voltage requirements for your part.

NOTES:

For a definition of STD, VR, VRE, MD, VRE/MD, refer to Specification Changes 2 and 18 in this document. ES refers to Engineering Samples. DP indicates that this part can only be used as a dual processor.  CPU Type of  "2"  or  "0 or 2"  indicates this part supports dual processing.

The Type corresponds to bits [13:12] of the EDX register after RESET, bits [13:12] of the EAX register after the CPUID instruction is executed. This is shown as 2 different values based on the operation of the device as the primary processor or the dual processor upgrade.

The Family corresponds to bits [11:8] of the EDX register after RESET, bits [11:8] of the EAX register after the CPUID instruction is executed.

The Model corresponds to bits [7:4] of the EDX register after RESET, bits [7:4] of the EAX register after the CPUID instruction is executed.

The Stepping corresponds to bits [3:0] of the EDX register after RESET, bits [3:0] of the EAX register after the CPUID instruction is executed.

• TCASE = 60C.
• VRT  Intel's Voltage Reduction Technology: The VCC for I/O is 3.3V,  but the core VCC, accounting for about 90% of power usage, is reduced to 2.9V, to reduce power consumption and heating.
• No Kit   means that part meets the specifications but is not tested  to support 82498/82493 and 82497/82492 cache timings
• STEPPING The cB1 stepping is logically equivalent to the C2-step, but on a different manufacturing process.  The mcB1 step is logically equivalent to the cB1 step  (except it does not support DP, APIC or   FRC).
  The mcB1, mA1, mA4 and mcC0-steps also use Intel's VRT (Voltage Reduction Technology, see note 2 above) and are available in the TCP and SPGA package, primarily to support mobile applications.  All mobile steppings are distinguished by an additional "m" prefix, for "mobile".
• This is a boxed Pentium processor without the attached fan heatsink.
• This is a boxed Pentium processor with an attached fan heatsink.
• These parts do not support boundary scan.  S106J was previously marked  (and is the same as) SK106J.
• DP, FRC and APIC features are not supported on these parts.
• These parts are packaged in the Plastic Pin Grid Array (PPGA) package.  For additional specifications of this package, see specification clarifications 27 and 28.

So what is a stepping?

Answer:

The first version of a new microprocessor product is the A-0 step; later as we make improvements to the product for functional (bug) fixes or manufacturing improvements we will increase the stepping number. Generally speaking, minor changes result in an increased number, (i.e. A-3 to A-4) while more complex changes result in the letter being changed.(i.e. A-3 to B-0)

If you would like to know which stepping of the Pentium® processor you have, the CPUID utility program will report this information. Each manufacturing stepping has a unique stepping ID which can be read by the CPUID program.