1. Recently, I have done some sketchy investigation of MCUs. A full list is not possible, and I focus on four major ones: Microchip, Atmel, Arm, and Renesas. The vendors, applications are discussed bellow. Renesas is #1 MCUs vendor, Microchip is #1 8-bit MCUs vendor, Atmel is a vendor with fastest growth in 8-bit MCUs, and Arm is #1 used IP core of architecture.
2. Classes of MCUs
The MCUs could be split into three kinds, low end, medium end and high end. Low end means the 8-bit MCUs, medium end means 16/32-MCUs, and high end means the 32-bit MCUs (maybe more than one core right now). 16-bit MCUs may be ignorable, for they seem to come to end, for the existence of 8-bit MCUs and the lower cost of 32-bit MCUs.
Low end MCUs focus on low cost, and are applied in small situations, like IC cards, pseudo random number generator, lighting devices, motor controller, etc. Ex, Arm Cortex-M series of Arm(use the Thumb/Thumb2 instruction set), pic 16/18/24 series of Microchip, 80C51, AVR-8 of Atmel, RL78 of Renesas.
Medium end MCUs focus on higher performance and applied in more complicated situations, like remoter monitor, IP camera, set op boxes, digital TV, media players, cameras, hard disk drives, networking, printing, dependable systems in medical/industrial/automotive, IH cooking heaters, air conditioners, washing machines, digital cameras. Ex, Cortex-R series of Arm, pic 32 series of Microchip,AVR-32 of Atmel, RX of Renesas.
High end MCUs focus on more performance (usually a rich OS platform is supported), and applied in situations like: smartphones, mobile computing, digital TV, set-up boexes, and even servers. For example, the iphone 4, ipad2, and Sansung waver use Cortex-A8. Ex, Cotex-A series of Arm, VR of Renesas.
3. Hardware features
Low end MCUs: are basically so simple that, no cache, up to 128K/536K flash memory, up to 4k/96K ram, optional 4K EEPROM.
pic8: no cache, up to 128K flash memory, up to 4K ram
pic24: no cache, up to 536K flash memory, up to 96K ram, 4K EEPROM.
tinyAVR8: no cache, up to 8K flash, upto 0.5K sram, up to 512B EEPROM.
megaAVR8: no cache, up to 128K flash, no ram.
AVR XMEGA8: no cache, up to 256K flash, up to 16K sram, up to 4K EEPROM.
78K0-8: no cache, up to 60K flash, up to 3K ram.
RL78-16: no cache, up to 512K flash, up to 32K ram.
Medium end MCUs:
Cotex-R: optinal 4-64K cache.
pic32: no cache, up to 512K flash, up to 128K sram, prefetch buffer cache.
AVR32: no cache, up to 512K flash, up to 128K dram
RX-32: no cache, up to 256K flash, up to 32K ram.
High end MCUs:
Cotex-A: up to 64K L1 cache, up to 4M L2 cache, up to 1T memory is accessible.
VR-64: 2-way, up to 32K I/D cache.
