The Life Cycle of a CPU

In today's time a CPU may only stay on the market for 24 months, some even less before it is replaced by something new and greater. More features, more cache, today's market begs, even cries for more, and CPU manufacturers are quick to jump in with something new, but not always great. This was not always so.

There was a time not so long ago when people begged for more, and CPU manufacturers strained to produce but were not always successful. Often new designs WERE created that WERE better, but the price was absolutely insane. This led to the older CPUs continued production and use. Sometimes for many, many years past its release date. Speeds would increase (or not), power consumption and die size would be reduced, often the supply or I/O voltages would be designed to work at lower levels but still be 'tolerant' to the original specifications.

It is important to see this life cycle of CPUs as they matured in the market to realize the importance of some of these historic chips. Chips designed in the 1970s are STILL being made. Where as some chips designed in the 1990s lasted for but a few months. I will start with the 1970s with such famous chips as the Intel 4004 and the MOS 6502 and slowly we will look forward to the 1990's.

CPU Type	Introduced	Last Production	Lifetime		Notes:
Intel 4004	1971	1981	10
Intel 8008	1972	1983	11
Intel 8080	1974	1990	16
Intel 4040	1974	1981	7
Motorola 6800	1974	2006	32
TI TMS1000	1974	1985	11
Microchip PIC16	1975	2009	34
MOS 6502	1975	2009	34		SS
AMD 2901	1975	2009	34		SS
Zilog Z80	1976	2009	33
Intel 8085	1976	2000	24		SS
Fairchild 3850	1976	1984	8
Signetics 2650	1976	1987	11
Intel MCS-48	1976	2009	33		SS
RCA 1802	1977	1995	18		SS
Intel 8086	1978	1998	20		SS
Intel 8088	1979	1998	19		SS
Motorola 68000	1979	2009	30
Intel MCS-51	1980	2009	29		SS
Intel 80186/8	1982	2009	27		SS
Intel 80286	1982	1991	9		SS
NEC V20	1984	1995	11
Intel 80386	1985	2007	22		EMB
AMD 29000	1987	1996	9
Intel i960	1988	2007	19
Intel i486	1989	2007	16		EMB
AMD 29050	1990	2005	15		SS
AMD 29030	1991	1998	7
Digital 21064	1991	1997	6
Intel Pentium	1993	2009	16
Intel Pentium II	1995	2001	6
Cyrix 6x86	1995	2000	5
AMD K5	1996	1998	2
Sun UltraSparc II	1996	2001	5
AMD K6	1997	1998	1
IDT Winchip	1997	2000	3
AMD K6-2	1998	2001	3
Intel Pentium III	1999	2009	10

Notes:

SS - Last produced by a Second Source

EMB: Embedded Version (made by third party) was the last produced

It is very apparent what is happening here. CPUs introduced in the late 1970's and early 1980's are often still in use today. Why is this so? Certainly today's designs are much more robust however, when you design a printer or a sewing machine you do not want a P4 or a AMD K6 to power it. You want something simple, cheap and easy to use. Something like a Zilog Z80, MOS 6502 or NEC 7810 is ALL many applications need. They have the added benefit of having HUGE code bases (amount of software ALREADY written for them). In other words, if it aint broke, don't fix it.

If you look closely at the types of CPUs made late in the life cycle you will see a shift in production from commercial spec chips to chips that are T, I and M spec. Extended Temperature, Industrial, and Military. All areas where one wants something to work the same way always. These markets are some of the biggest for 'old' CPUs. It works fine for them, and is not near as sensitive as modern CPUs to variations in voltage and temperature. A lot of these industrial chips will allow a 15% fluctuation in voltage, at temperatures from -50C to 125C. Try THAT with a P4.

Today's modern CPUs are VERY specialized. Yes you can run about 100,000 applications on an AMD K6 on your PC, but where else do you see AMD K6 CPUs? That's right, they ONLY exist in computers (or computerized routers). Most all computing needs are NOT sitting on your desk so you can surf eBay and play Doom III, they are in your car, your cell phone, your printers and even your microwave. Control applications account for 90% of the CPU market.

In the last few years Intel has been working hard to gain back alot of the embedded customers they once had. With their new CPUs (Atom etc) they will have several specs that they guarentee an End-Of-Life no earlier then 7 years from when it first comes out. This gives engineers a bit more breathing room in their design life analysis.

. If I placed the ARM core or any of the MIPS cores in this list you would see them still in production. Why? because they are simple (RISC based in most cases) CPUs that lend themselves to MANY different applications. They are useless for the PC (Ask Acorn computers about ARM devices in the PC ;)) but for anything else in the world they work great.

Something else of interesting note: Speed
Or the lack of, many of the 'old' CPUs still in production are being made at exactly the same speed as they were when they were introduced, or not much faster. The 6502 made now by WDC is clocked at the SAME speed as 30 years ago. The Zilog Z80 has been clocked up to 20MHz but is still available at 6Mhz. The Intel i186 is the exact same thing, still available at its initial speed.

The MCS-51 is a different story. It is a very robust architecture and lends itself to high clock speeds. It was released at 12MHz in 1980 and stayed at 12MHz for 15 years or more. There are now several companies making hi-speed 8051 solutions (Dallas-Maxim @ 50 MHz, Si-Labs (formerly Cygnal) @ 100MHz, Atmel @ 33MHz). This is because the 8051 is so easy to program and work with and actually benefits from higher clocks.