3 ms·

So AIUI this is explicitly trying to be smaller than 32-bit RISC-V. And I can see that in the abstract, but I gotta ask: How much does it matter? My very uninfo

So AIUI this is explicitly trying to be smaller than 32-bit RISC-V. And I can see that in the abstract, but I gotta ask: How much does it matter? My very uninformed impression was that with current fabrication, RISC-V is already more than small enough (on-chip surface area) and cheap enough ($) that there's not a lot of market for anything underneath it. Am I mistaken? (To be clear, I'd like it to work, just questioning the economics.)

cmrdporcupine 2y ago
Sometimes there doesn't need to be a "market", just an interest and passion. I think there's value in an open and modernized 8-bit MCU/MPU that isn't PIC or whatever.
- PaulHoule 2y ago
  I love AVR-8 myself.
  - garaetjjte 2y ago
    It's really terrible that for cheap embedded cores things like 8051 are still being used, instead of sane architectures like AVR.
    - PaulHoule 2y ago
      I find it pretty scary that C compilers target the 8051 but I also think C is a terrible waste of the AVR-8 (who needs to move the stack pointer around meaninglessly in a simple program where recursion is a problem and not a solution? Probably the best thing that happened in the 1970s was that Microsoft BASIC beat Lisp and Logo, otherwise a generation of people learning to code would have been victimized even more by bad Fibonacci implementations) which I only indulge in because I can port C code to a bigger microcontroller.
      - cmrdporcupine 2y ago
        Have you ever played with the Parallax Propeller MCUs? (I and II). 32-bit, but very "retro" feel to them. And an odd and interesting multicore architecture. Unfortunately they've had a bad streak in terms of getting a proper GCC or Clang toolchain targeted towards them. The developers of the chip are focused on their own weird structured BASIC-Assembly fusion ("SPIN").
MisterTea 2y ago
They state this as their reasoning so there must be merit in pursuing a smaller footprint: > Current industry trends are to adapt 32-bit RISC IP for microcontroller use, however their large 32x32 register files and loosely encoded instructions limit their absolute minimum footprint. So with the goal of a creating a performance and compact microprocessor IP, we need an 16-bit instruction set architecture (ISA). Not every application requires 32 bits and as you can see from some of the use cases, there might be a dozen of these in a design so minimal footprint is important.
- RetroTechie 2y ago
  Some 8-bit cpus allow combining some registers in pairs. Giving 16-bit values from otherwise 8-bit registers. Or have a few dedicated 16-bit registers. Couldn't the same be done in a 16-bit architecture? And cut the # of registers. Like 16x 16-bit registers, optionally used as 32-bit pairs (8 of those). None of this says anything about external memory sizes or such. Btw: RISC-V has an "-E" flavour which cuts the # of registers in half from 32 to 16, but is otherwise identical. There's even some (unofficial) RV16 candidates out there.
  - tredre3 2y ago
    I think part of the goal for Turbo9 is to be used in the real world. By using an established ISA and maintaining binary compatibility, their CPU can be targeted by any tooling built for it over the past 40 years. Think of it: all existing documentation, code, compilers, assemblers, know-how, even existing compiled binaries! As soon as you create your own architecture, you're essentially a toy. Nobody will want to rely on your half finished C compiler for it, or your unmaintained patchset for LLVM, or be willing to learn verilog just to fill gaps in documentation. Even something as "simple" as changing registers on RISC-V will break most tooling and make most existing documentation impossible to rely on. Resulting in essentially a new architecture with a confusing name. Being a toy isn't a bad thing, it just wasn't their goal here.
userbinator 2y ago
that there's not a lot of market for anything underneath it. You'd be very mistaken. 4-bit MCUs are still found in places where you wouldn't even expect an MCU, and the 8-bit ones are numerous in ultra-high-volume highly cost-sensitive applications. Products that use COB-mounted sub-$0.01 die.

cmrdporcupine 2y ago

Sometimes there doesn't need to be a "market", just an interest and passion. I think there's value in an open and modernized 8-bit MCU/MPU that isn't PIC or whatever.

PaulHoule 2y ago
I love AVR-8 myself.
- garaetjjte 2y ago
  It's really terrible that for cheap embedded cores things like 8051 are still being used, instead of sane architectures like AVR.
  - PaulHoule 2y ago
    I find it pretty scary that C compilers target the 8051 but I also think C is a terrible waste of the AVR-8 (who needs to move the stack pointer around meaninglessly in a simple program where recursion is a problem and not a solution? Probably the best thing that happened in the 1970s was that Microsoft BASIC beat Lisp and Logo, otherwise a generation of people learning to code would have been victimized even more by bad Fibonacci implementations) which I only indulge in because I can port C code to a bigger microcontroller.
    - cmrdporcupine 2y ago
      Have you ever played with the Parallax Propeller MCUs? (I and II). 32-bit, but very "retro" feel to them. And an odd and interesting multicore architecture. Unfortunately they've had a bad streak in terms of getting a proper GCC or Clang toolchain targeted towards them. The developers of the chip are focused on their own weird structured BASIC-Assembly fusion ("SPIN").

MisterTea 2y ago

They state this as their reasoning so there must be merit in pursuing a smaller footprint: > Current industry trends are to adapt 32-bit RISC IP for microcontroller use, however their large 32x32 register files and loosely encoded instructions limit their absolute minimum footprint. So with the goal of a creating a performance and compact microprocessor IP, we need an 16-bit instruction set architecture (ISA). Not every application requires 32 bits and as you can see from some of the use cases, there might be a dozen of these in a design so minimal footprint is important.

RetroTechie 2y ago
Some 8-bit cpus allow combining some registers in pairs. Giving 16-bit values from otherwise 8-bit registers. Or have a few dedicated 16-bit registers. Couldn't the same be done in a 16-bit architecture? And cut the # of registers. Like 16x 16-bit registers, optionally used as 32-bit pairs (8 of those). None of this says anything about external memory sizes or such. Btw: RISC-V has an "-E" flavour which cuts the # of registers in half from 32 to 16, but is otherwise identical. There's even some (unofficial) RV16 candidates out there.
- tredre3 2y ago
  I think part of the goal for Turbo9 is to be used in the real world. By using an established ISA and maintaining binary compatibility, their CPU can be targeted by any tooling built for it over the past 40 years. Think of it: all existing documentation, code, compilers, assemblers, know-how, even existing compiled binaries! As soon as you create your own architecture, you're essentially a toy. Nobody will want to rely on your half finished C compiler for it, or your unmaintained patchset for LLVM, or be willing to learn verilog just to fill gaps in documentation. Even something as "simple" as changing registers on RISC-V will break most tooling and make most existing documentation impossible to rely on. Resulting in essentially a new architecture with a confusing name. Being a toy isn't a bad thing, it just wasn't their goal here.

userbinator 2y ago

that there's not a lot of market for anything underneath it. You'd be very mistaken. 4-bit MCUs are still found in places where you wouldn't even expect an MCU, and the 8-bit ones are numerous in ultra-high-volume highly cost-sensitive applications. Products that use COB-mounted sub-$0.01 die.