Hardware Reference
In-Depth Information
or tips on their websites listing any problems or special fixes or patches for their chips.
Previously, the only way to fix a processor bug was to work around it or replace the chip with
one that had the bug fixed. Starting with the Intel P6 and P7 family processors, including the
Pentium Pro through Pentium D and Core i7, many bugs in a processor's design can be fixed by
altering the microcode in the processor. Microcode is essentially a set of instructions and
tables in the processor that control the way the processor operates. These processors
incorporate a new feature called reprogrammable microcode, which enables certain types of
bugs to be worked around via microcode updates. The microcode updates reside in either the
motherboard ROM BIOS or Windows updates and are loaded into the processor by the
motherboard BIOS during the POST or by Windows during the boot process. Each time the
system is rebooted, the updated microcode is reloaded, ensuring that it will have the bug fix
installed anytime the system is operating.
The updated microcode for a given processor is provided by Intel to either the motherboard
manufacturers or to Microsoft so the code can be incorporated into the flash ROM BIOS for the
board, or directly into Windows via Windows Update. This is one reason it is important to
keep Windows up to date, as well as to install the most recent motherboard BIOS for your
systems. Because it is easier for most people to update Windows than to update the
motherboard BIOS, it seems that more recent microcode updates are being distributed via
Microsoft than the motherboard manufacturers.
Processor Code Names
Intel, AMD, and VIA have always used code names when talking about future processors and
processor cores. The code names usually are not supposed to become public, but they often do. They
can often be found in online and print news and magazine articles talking about future-generation
processors. Sometimes they even appear in motherboard manuals because the manuals are written
before the processors are officially introduced.
Intel publishes a fairly complete list of processor, chipset, motherboard, and even Ethernet controller
code names on its website (
http://ark.intel.com/#codenames
)
. AMD doesn't provide a single
document on its site for its code names, but you can use a Google search such as “code name”
site:amd.com to find documents on the AMD website that contain code names. You can also find
information on other sites by doing a search.
P1 (086) Processors
Intel introduced the 8086 back in June 1978. The 8086 was one of the first 16-bit processor chips on
the market; at the time, virtually all other processors were 8-bit designs. The 8086 had 16-bit internal
registers and could run a new class of software using 16-bit instructions. It also had a 16-bit external
data path, so it could transfer data to memory 16 bits at a time. It contained 29,000 transistors and
could run at clock speeds of up to 5MHz.
The address bus was 20 bits wide, which enabled the 8086 to address a full 1MB (2
20
) of memory.
This was in stark contrast to most other chips of that time that had 8-bit internal registers, an 8-bit
external data bus, and a 16-bit address bus allowing a maximum of only 64KB of RAM (2
16
).
Although not directly backward compatible with the 8080, the 8086 instructions and language were
