Which is a board list. That is a problem, unless you know of a supported board and you know if uses the MCU you are trying to find out, it is difficult to search.
Reading for instance this random board
The comment say it should be ATMega2560, but none of the settings explicitely define this.
I am trying where the specific MCU is defined ? What specific command ? Perhaps from that command I could find a direct list of supported MCUs ?
This is probably speaking out of turn, but I would consider the most authoritative resource for finding out whether or not a specific MCU is supported is to SSH into your printer, execute make menuconfig and search for the device you’re looking for:
ESP8266 <- Not supported
ESP32 <- Not Supported
CH32V003 <- Not Supported
STM32F103C8T6 < "STM32F103" is and I believe the 'C8T6 is part of that family
atmega328p < Supported
rp2040 < Supported
Searching for “Processor model”, looks like the answer spreads all around the code base in files called Kconfig, those that have a section “config MCU”
For instance
config MCU
string
default "atmega168" if MACH_atmega168
default "atmega328" if MACH_atmega328
default "atmega328p" if MACH_atmega328p
default "atmega1284p" if MACH_atmega1284p
default "atmega644p" if MACH_atmega644p
default "at90usb1286" if MACH_at90usb1286
default "at90usb646" if MACH_at90usb646
default "atmega32u4" if MACH_atmega32u4
default "atmega1280" if MACH_atmega1280
default "atmega2560" if MACH_atmega2560
So the exhaustive list would be
default "sam3x8e" if MACH_SAM3X8E
default "sam3x8c" if MACH_SAM3X8C
default "sam4s8c" if MACH_SAM4S8C
default "sam4e8e" if MACH_SAM4E8E
default "same70q20b" if MACH_SAME70Q20B
default "samc21g18a" if MACH_SAMC21G18
default "samd21g18a" if MACH_SAMD21G18
default "samd21e18a" if MACH_SAMD21E18
default "samd21j18a" if MACH_SAMD21J18
default "samd21e15a" if MACH_SAMD21E15
default "samd51g19a" if MACH_SAMD51G19
default "samd51j19a" if MACH_SAMD51J19
default "samd51n19a" if MACH_SAMD51N19
default "samd51p20a" if MACH_SAMD51P20
default "same51j19a" if MACH_SAME51J19
default "same54p20a" if MACH_SAME54P20
default "atmega168" if MACH_atmega168
default "atmega328" if MACH_atmega328
default "atmega328p" if MACH_atmega328p
default "atmega1284p" if MACH_atmega1284p
default "atmega644p" if MACH_atmega644p
default "at90usb1286" if MACH_at90usb1286
default "at90usb646" if MACH_at90usb646
default "atmega32u4" if MACH_atmega32u4
default "atmega1280" if MACH_atmega1280
default "atmega2560" if MACH_atmega2560
default "HC32F460"
default "lpc1768" if MACH_LPC1768
default "lpc1769" if MACH_LPC1769
default "rp2040"
default "stm32f031x6" if MACH_STM32F031
default "stm32f042x6" if MACH_STM32F042
default "stm32f070xb" if MACH_STM32F070
default "stm32f072xb" if MACH_STM32F072
default "stm32f103xe" if MACH_STM32F103
default "stm32f207xx" if MACH_STM32F207
default "stm32f401xc" if MACH_STM32F401
default "stm32f405xx" if MACH_STM32F405
default "stm32f407xx" if MACH_STM32F407
default "stm32f429xx" if MACH_STM32F429
default "stm32f446xx" if MACH_STM32F446
default "stm32f765xx" if MACH_STM32F765
default "stm32g070xx" if MACH_STM32G070
default "stm32g071xx" if MACH_STM32G071
default "stm32g0b0xx" if MACH_STM32G0B0
default "stm32g0b1xx" if MACH_STM32G0B1
default "stm32g431xx" if MACH_STM32G431
default "stm32h723xx" if MACH_STM32H723
default "stm32h743xx" if MACH_STM32H743
default "stm32h750xx" if MACH_STM32H750
default "stm32l412xx" if MACH_STM32L412
default "stm32f103xe" if MACH_N32G45x
I wonder what these are … Could it run off x86 or linux with GPIO/SPI/I2C ports ?
AR100 ?
generic ?
linux ?
pru ?
simulator ?
I asked chatgpt to clean that up a bit, here is the result
Atmel SAM3 Series
sam3x8e // High performance and connectivity features
sam3x8c
Atmel SAM4 Series
sam4s8c // Superior performance in signal processing
sam4e8e // Enhanced networking capabilities
Atmel SAME Series
same70q20b // High-performance ARM Cortex-M7 based MCU
same51j19a // Cortex-M4 with Low Power and Enhanced Analog Features
same54p20a // High performance with advanced connectivity
Atmel SAMC Series
samc21g18a // Cortex-M0+ with CAN-FD feature
Atmel SAMD Series
samd21g18a
samd21e18a
samd21j18a
samd21e15a // Lower pin count and memory variant
samd51g19a // High performance Cortex-M4
samd51j19a
samd51n19a
samd51p20a // Advanced features with more pins and memory
Atmel ATmega Series
atmega168
atmega328
atmega328p // picoPower technology for low power consumption
atmega1284p // Large memory capacity
atmega644p
atmega32u4 // USB 2.0 Full-speed/low-speed Device Module with Interrupt on Transfer Completion
atmega1280 // High memory density
atmega2560 // Extended memory and peripherals
Atmel AT90 Series
at90usb1286 // USB functionality
at90usb646
HC32 Series
HC32F460 // General purpose ARM Cortex-M4 MCU
NXP LPC Series
lpc1768 // Extensive peripheral integration
lpc1769 // Higher frequency variant of LPC1768
Raspberry Pi
rp2040 // Dual-core ARM Cortex-M0+ processor with flexible IO
STMicroelectronics STM32 Series
stm32f031x6 // Basic ARM Cortex-M0 MCU
stm32f042x6 // USB capabilities
stm32f070xb
stm32f072xb // Improved connectivity
stm32f103xe // High performance Cortex-M3
stm32f207xx // Advanced connectivity and performance
stm32f401xc // Balance of power and performance
stm32f405xx // Rich in connectivity features
stm32f407xx // Enhanced features for digital signal processing
stm32f429xx // Advanced graphics and high computation power
stm32f446xx // Enhanced cryptographic and DSP capabilities
stm32f765xx // Advanced performance with large memory
stm32g070xx // Cost-effective Cortex-M0+
stm32g071xx // General purpose Cortex-M0+
stm32g0b0xx // Entry level with advanced peripherals
stm32g0b1xx // Bigger memory with advanced features
stm32g431xx // High performance with motor control peripherals
stm32h723xx // High performance Cortex-M7
stm32h743xx // Very high performance with large internal memory
stm32h750xx // High performance with cost-efficient memory usage
stm32l412xx // Ultra-low-power Cortex-M4
Perhaps that list could be included in the Klipper documentation.