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Comment on TKey: A reasonably secure RISC-V computer in a USB stick

dragontamer@lemmy.world ⁨9⁩ ⁨months⁩ ago

Ehhhh… I’d recommend a Teensy instead, or a variety of other microprocessors. At $72, this is awful value. And there seems to be no specifications with regards to power-consumption.

www.pjrc.com/store/teensy41.html

Teensy gives you 100 MBit Ethernet, USB, 600MHz, 1024kB of SRAM for like $35 and within ~100mA of current usage at this 600MHz speed, meaning it easily runs off of AA Batteries for over a day with just a bit of idle/sleep cycles.

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dannym@lemmy.escapebigtech.info ⁨9⁩ ⁨months⁩ ago
there are use cases, such as security, where you want as few instructions as possible, so a full ARM processor isn’t the best idea

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- dragontamer@lemmy.world ⁨9⁩ ⁨months⁩ ago
  On the contrary, RISC-V is typically bigger and less efficient than Cortex-M7 on the Teensy.
  
  There are 10-cent ARM Cortex M0+ processors (M0+ being the smallest ARM). M7 is kinda-small. ARM scales to different sizes and power-efficiencies.
  
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  - dannym@lemmy.escapebigtech.info ⁨9⁩ ⁨months⁩ ago
    [deleted]
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    dragontamer@lemmy.world ⁨9⁩ ⁨months⁩ ago
    
    in this case the instruction set is extremely small
    
    developer.arm.com/…/Instruction-set-summary
    
    So is the Cortex M7. The entirety of the M0+, M4, and M7 microcontroller cores are very, very small ARMs.
    
    iCE40 DSPs
    
    Hmmm. Okay, so its an FPGA Risc-V then.
    
    That’s kind of sad, that means there’s no hope that its as power-efficient as a proper ASIC core like ARM-M7.
    
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Cenzorrll@lemmy.world ⁨9⁩ ⁨months⁩ ago
Completely different use cases

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- dragontamer@lemmy.world ⁨9⁩ ⁨months⁩ ago
  How so?
  
  The use-case is determined by power-efficiency, performance, and cost. Cost is already a loser at $72 vs $35. Performance is a loser at 18MHz vs 600MHz. What’s left is power-efficiency, but now that I know that this is an FPGA soft-core, I’m guessing the Teensy / ARM Cortex-M7 is also more power efficient.
  
  So the Teensy is cheaper, faster, and (probably??) more power-efficient than the RISC-V soft-core FPGA implementation here.
  
  The 8-bit uCs that I like to play with (AVR, or their competitors PIC12, Cortex M0+, Cortex M32, or TI MSP430) are all in the 5mA or less range (dramatically so: some in the 5uA range if you abuse sleep / idle states severely). These 8-bitters are closer to the performance that I’d expect of the 18MHz speed and 128kB of RAM here, but I have reason to believe that the 8-bit (and 32-bit / 16-bit competitors like Cortex M0+ / MSP430) are far more power efficient than the TKey.
  
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