4 ms·

I wonder if it's the beginning of the end 8-bit and 16-bit micro. Prices of 32-bit micros are so low now, they are so small, it just doesn't seem worth the hass

by FigBug 13y ago

I wonder if it's the beginning of the end 8-bit and 16-bit micro. Prices of 32-bit micros are so low now, they are so small, it just doesn't seem worth the hassle of dealing with an 8/16bit. I'm sure they'll exist in legacy designs for another 20+ years, but new designs? Less and less.

sokoloff 13y ago
Power budget is still a big deal, and in a lot of applications is a bigger concern than the BOM parts cost. Related: Atmel's got tiny 8-bit micros that can run off 0.7V, making it feasible to run off a single alkaline cell.
rational_indian 13y ago
8 bit code takes much less space than 32bit code. You can almost pack in 2 to 4 times as much code in the same space as fixed instruction width 32bit code. Perhaps less when compared with ARM thumb but still significant.
- sitkack 13y ago
  Flash memory used for program storage is much much cheaper than ram. One of the only wins that 8 bit code has over even thumb code is a faster instruction bus, but for a pipelined processor that doesn't matter anymore. 8 bit would be dead if the 32 bit parts included all of the peripherals engineers actually need to build stuff (SPI,analog,timers,etc).
  - FigBug 13y ago
    There are lots of 32bit micros with all those peripherals, I think it's just that the embedded industry moves slowly and adopts new products with caution. I think it's only a matter of time before all microcontrollers are ARM and the various 8/16 bit architectures die off.
    - sitkack 13y ago
      There are, but the AVR parts for example have an amazing balanced of needed peripherals that still makes those parts attractive. It Atmel replaced their AVR cores with a cortex-m0 but kept all the peripherals in place and the pinouts and the part numbering scheme the same, they would have a huge boost in market share.
- joe_bleau 13y ago
  You'd think, right? Luckily the ARM dudes came up with Thumb-2, so most (all but 6) of the Cortex-M0+ instructions are actually 16 bit, not 32. (Nice chart at http://en.wikipedia.org/wiki/ARM_Cortex-M http://en.wikipedia.org/wiki/ARM_Cortex-M .) But what's even more interesting is to actually compile apps and compare code size. Miro Samek did this for a couple of RTOS-like framesworks and compared across a mix of 8, 16 and 32 bit micro architectures (PIC, 8051, M8C, 68HC08, AVR, MSP430, M16C, ARM7 Thumb, and ARM Cortex-M3 Thumb2). For his test, the MSP430 was the most dense, but Thumb2 wasn't far behind. (http://embeddedgurus.com/state-space/2009/03/insects-of-the-computer-world/ http://embeddedgurus.com/state-space/2009/03/insects-of-the-...) Of course, there are 4 bit micros out there...
  - lgeek 13y ago
    > ARM dudes came up with Thumb-2 I guess I'm nitpicking, but Cortex-M0+ and Cortex-M0 are basically Thumb only. The only Thumb-2 instructions implemented by these cores are the ones for barriers and transferring data between general purpose registers and special registers. These are: 1) Without an equivalent Thumb instruction 2) Required on the ARM architecture 3) A tiny, tiny percentage of instructions executed or just not used by typical application code. Regarding the linked test, the toolchain and optimisation flags are going to make a significant difference. I wonder how GCC (which is free and probably the most popular) and armcc (which generally produces significantly better output) would fit in there.
  - userbinator 13y ago
    Here's another interesting comparison of code density, in which x86 (not surprisingly?) came out ahead: http://www.researchgate.net/publication/224114307_Code_density_concerns_for_new_architectures/file/32bfe5118fd8e27899.pdf http://www.researchgate.net/publication/224114307_Code_densi...
userbinator 13y ago
Actually 4-bit MCUs (mostly mask-programmed) are still quite popular at the extreme low end, because they're absolutely tiny (<1mm^2 bare die, in COB packaging) and cheap (<$0.01) and good enough for their application; ultracheap 4-function calculators, electric teethbrush, multifunction flashlights, toys, etc.

by FigBug 13y ago

sokoloff 13y ago

Power budget is still a big deal, and in a lot of applications is a bigger concern than the BOM parts cost. Related: Atmel's got tiny 8-bit micros that can run off 0.7V, making it feasible to run off a single alkaline cell.

rational_indian 13y ago

8 bit code takes much less space than 32bit code. You can almost pack in 2 to 4 times as much code in the same space as fixed instruction width 32bit code. Perhaps less when compared with ARM thumb but still significant.

sitkack 13y ago
Flash memory used for program storage is much much cheaper than ram. One of the only wins that 8 bit code has over even thumb code is a faster instruction bus, but for a pipelined processor that doesn't matter anymore. 8 bit would be dead if the 32 bit parts included all of the peripherals engineers actually need to build stuff (SPI,analog,timers,etc).
- FigBug 13y ago
  There are lots of 32bit micros with all those peripherals, I think it's just that the embedded industry moves slowly and adopts new products with caution. I think it's only a matter of time before all microcontrollers are ARM and the various 8/16 bit architectures die off.
  - sitkack 13y ago
    There are, but the AVR parts for example have an amazing balanced of needed peripherals that still makes those parts attractive. It Atmel replaced their AVR cores with a cortex-m0 but kept all the peripherals in place and the pinouts and the part numbering scheme the same, they would have a huge boost in market share.
joe_bleau 13y ago
You'd think, right? Luckily the ARM dudes came up with Thumb-2, so most (all but 6) of the Cortex-M0+ instructions are actually 16 bit, not 32. (Nice chart at http://en.wikipedia.org/wiki/ARM_Cortex-M http://en.wikipedia.org/wiki/ARM_Cortex-M .) But what's even more interesting is to actually compile apps and compare code size. Miro Samek did this for a couple of RTOS-like framesworks and compared across a mix of 8, 16 and 32 bit micro architectures (PIC, 8051, M8C, 68HC08, AVR, MSP430, M16C, ARM7 Thumb, and ARM Cortex-M3 Thumb2). For his test, the MSP430 was the most dense, but Thumb2 wasn't far behind. (http://embeddedgurus.com/state-space/2009/03/insects-of-the-computer-world/ http://embeddedgurus.com/state-space/2009/03/insects-of-the-...) Of course, there are 4 bit micros out there...
- lgeek 13y ago
  > ARM dudes came up with Thumb-2 I guess I'm nitpicking, but Cortex-M0+ and Cortex-M0 are basically Thumb only. The only Thumb-2 instructions implemented by these cores are the ones for barriers and transferring data between general purpose registers and special registers. These are: 1) Without an equivalent Thumb instruction 2) Required on the ARM architecture 3) A tiny, tiny percentage of instructions executed or just not used by typical application code. Regarding the linked test, the toolchain and optimisation flags are going to make a significant difference. I wonder how GCC (which is free and probably the most popular) and armcc (which generally produces significantly better output) would fit in there.
- userbinator 13y ago
  Here's another interesting comparison of code density, in which x86 (not surprisingly?) came out ahead: http://www.researchgate.net/publication/224114307_Code_density_concerns_for_new_architectures/file/32bfe5118fd8e27899.pdf http://www.researchgate.net/publication/224114307_Code_densi...

userbinator 13y ago

Actually 4-bit MCUs (mostly mask-programmed) are still quite popular at the extreme low end, because they're absolutely tiny (<1mm^2 bare die, in COB packaging) and cheap (<$0.01) and good enough for their application; ultracheap 4-function calculators, electric teethbrush, multifunction flashlights, toys, etc.