
RIP 8 Bit? - bdfh42
http://www.drdobbs.com/blog/archives/2010/04/rip_8_bit.html
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pixelbath
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.

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NateLawson
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...](http://rdist.root.org/2009/01/21/introducing-xum1541-the-
fast-c64-floppy-usb-adapter/))

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.

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ladyada
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.

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sketerpot
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).

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maroc
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.

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

~~~
chbarts
Dr. Dobb's is certainly closer to being dead than 8-bit microcontrollers are.
It ceased publication as a standalone magazine in February 2009; it's now
online and a monthly section in _InformationWeek_ called _Dr. Dobb's Report._

