RIP 8 Bit?

Ugh, dislike sites that require an independent registration to post a single comment.

On topic, I doubt lower-power microprocessors will be going anywhere for a while. Sure, you can stick an ARM in there, but what about battery life? You might save money and effort, but if power consumption is an issue, you have to weigh your priorities.

I don't get the author's point. It seems to be "because 8-bit micros are so cheap, don't design with discrete components". This is valid and has in fact been the goal since the MOS 6502 in 1975 ($25 vs. $300 for an Intel 8080 or Motorola 6800). But he goes on to say "thus, 8-bit micros are themselves going away".

The second part is just not true, nor does he offer any evidence for it. He points out this deficiency in his argument himself by noting that many 555s (mid-70's design) are still available.

I think a better point to make is to watch the applications for parts as they age. You could buy 8-bit home computer from about 1975-1991. You could buy a 16-bit workstation from about 1981-1995. You can't buy either of those new today. Even your home office router is 32-bit.

However, 8-bit CPUs are still almost everywhere today. I designed a new hobbyist device with an 8-bit AVR with built-in USB DMA engine. (http://rdist.root.org/2009/01/21/introducing-xum1541-the-fas...)

The TI MSP430 series uses microamps and run off a small battery. The 8-bit CPU will always exist, it will just have more specialized onboard peripherals and be used for different applications.

One unit of measure I like to use is "word size vs. clock rate". For example, a Intel Core Solo running in 32-bit mode at 2.0 Ghz can represent ~2 seconds of clock cycles in a native word. A 16 Mhz AT90 can represent 0.004 seconds in its 16-bit word (actually 2 registers since it is 8-bit). So in general, the AT90 is a bit harder to program than the Intel CPU since you have to worry more about multi-byte arithmetic.

Another unit is clocks per byte of IO. With a gigabit ethernet adapter, the Intel machine has only 16 clocks/byte. Running at the full USB rate of 12 Mbit/s, the AT90 has 10.66 clocks/byte. So they both need hardware support to keep the pipe full.

It's fun to compare applications for various CPU types, but I don't think 8-bit is going to disappear even in the next 20 years.

well... yes, hobbyists have more choices about what to use - a 555 or a PIC or a laptop - and there's more bang for the $ with the new arm cortex chips. But when it comes to products, there are some very serious constraints with pricing and power usage. you can run a 555 on a single AAA battery and draw microamps, costs pennies, have multiple suppliers and have less complexity too. there are plenty of times you'd want that over a microprocessor.

Interestingly, from discussions with toy designers (barbies and such, with talking or moving parts) they all use the same 4-bit processor core that has a crummy audio playback module, some i/o and sensors. 4 bit! but its dirt cheap and well understood.

It's a little ridiculous that we can now get a microcontroller with a 50 MHz ARM Cortex-M0 core for $0.85 in bulk. Imagine how things will be in a few years (and a few more process nodes).

NXP (http://ics.nxp.com/products/mcus/cortex-m0/) and Energy Micro (http://energymicro.com/) are actively trying to kill the 8-bit MCU with their ARM Cortex-M(3|0) offerings. Very low power consumption on these chips.

But, still, they require a lot more external circuitry than an MSP430 or (SiLabs)C8051.

Off topic, but I thought Dr. Dobb's Journal was dead. Or was that just the print edition.