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Despite how simple and limited the 6502 is, it's always interesting to see this almost 50-year-old architecture being stretched to new limits. 6502 cores are st

Despite how simple and limited the 6502 is, it's always interesting to see this almost 50-year-old architecture being stretched to new limits. 6502 cores are still found in some SoCs aimed at the ultra-low-cost high-volume market.

dailykoder 3y ago
> 6502 cores are still found in some SoCs aimed at the ultra-low-cost high-volume market. What's the reason behind that? Probably just keeping existing, working designs and thus saving R&D costs? Sounds like beating a 10 cent risc-v core would be hard. Edit: When I first read your comment I had to chuckle a bit, because I got the image of a multicore SoC with 6502 6502 cores. That would be a fun project for my FPGA hmmmmmmmm ...
- themoonisachees 3y ago
  10c per part is incredibly high depending on how low-cost we're talking. If your chip needs very basic processing, and you're going to sell it for less than a cent per chip, you need your core to be basically free. Sure RISC-V is very inexpensive, but for parts like these risc is massive overkill and as a modern core, you'll be spending a lot of die area on a core that should really be an ASIC, but designing an ASIC is expensive so you can just slap a 6502 in that bad boy and call it a day. On the other end of the scale, you'd be surprised to learn that many chips you don't ever interface with as a user contain even ARM cores. These are usually ASICs in high-end products.
  - jeffgreco 3y ago
    Go on!
  - snvzz 3y ago
    >but for parts like these risc is massive overkill You seem to underestimate how small a RISC-V core can be. Take a look at SERV.
    - irdc 3y ago
      There’s also the cost of rewriting (yes, from assembler) all the existing code. And don’t forget QA.
    - monocasa 3y ago
      The area of just the register file (even for rv32e) is higher area than the survivors of the 8 bit ucontrollers.
      - snvzz 3y ago
        Not true for SERV vs 6502. SERV is smaller.
      - userbinator 3y ago
        16 registers * 32 bits * 4 transistors / cell = 2k transistors just for storing the bits alone, and that's not including the decoding and read/write circuitry.
        snvzz 3y ago
        There is no need to do weird math, as we know the actual numbers. 6502 has 3510 transistors. SERV at CMOS occupies 2.1kGE. SERV is smaller than 6502.
        monocasa 3y ago
        Gate Elements are multiple transistors. And that count doesn't include SERV's register file.
        snvzz 3y ago
        So you're saying they'd end up in the same ballpark? In that case, I'd rather have RISC-V's programming model.
        monocasa 3y ago
- deleted 3y ago
  [deleted]
- utensil4778 3y ago
  A lot of cheap USB1/2 widgets are actually a 6800 core. It's crazy how these old CPUs have stuck around for so long
ddingus 3y ago
There is a ton of code out there for pretty much any task you want. I have the 16 bit successor, the 65816, on a variable speed expansion card in my Apple 2. I run it in 8 bit mode most of the time mostly because it works and most library code is 8 bit. At those speeds, the chip is fast! Especially when one considers the simple model: ram clocked 1:1 with the cpu. In my case, I can run code over the 1Mhz bus, essentially turning most multi cycle ops into a single bus cycle per memory fetch. Or, the card has a megabyte of RAM and that runs at CPU speed. (0.15 to 16 Mhz) When doing that, it is fast enough to run large programs, written in higher level languages, at a useful speed. Of course Assembly language is crazy fast. It is a pretty fun environment to hack around in.

dailykoder 3y ago

> 6502 cores are still found in some SoCs aimed at the ultra-low-cost high-volume market. What's the reason behind that? Probably just keeping existing, working designs and thus saving R&D costs? Sounds like beating a 10 cent risc-v core would be hard. Edit: When I first read your comment I had to chuckle a bit, because I got the image of a multicore SoC with 6502 6502 cores. That would be a fun project for my FPGA hmmmmmmmm ...

themoonisachees 3y ago
10c per part is incredibly high depending on how low-cost we're talking. If your chip needs very basic processing, and you're going to sell it for less than a cent per chip, you need your core to be basically free. Sure RISC-V is very inexpensive, but for parts like these risc is massive overkill and as a modern core, you'll be spending a lot of die area on a core that should really be an ASIC, but designing an ASIC is expensive so you can just slap a 6502 in that bad boy and call it a day. On the other end of the scale, you'd be surprised to learn that many chips you don't ever interface with as a user contain even ARM cores. These are usually ASICs in high-end products.
- jeffgreco 3y ago
  Go on!
- snvzz 3y ago
  >but for parts like these risc is massive overkill You seem to underestimate how small a RISC-V core can be. Take a look at SERV.
  - irdc 3y ago
    There’s also the cost of rewriting (yes, from assembler) all the existing code. And don’t forget QA.
  - monocasa 3y ago
    The area of just the register file (even for rv32e) is higher area than the survivors of the 8 bit ucontrollers.
    - snvzz 3y ago
      Not true for SERV vs 6502. SERV is smaller.
    - userbinator 3y ago
      16 registers * 32 bits * 4 transistors / cell = 2k transistors just for storing the bits alone, and that's not including the decoding and read/write circuitry.
      - snvzz 3y ago
        There is no need to do weird math, as we know the actual numbers. 6502 has 3510 transistors. SERV at CMOS occupies 2.1kGE. SERV is smaller than 6502.
        monocasa 3y ago
        Gate Elements are multiple transistors. And that count doesn't include SERV's register file.
        snvzz 3y ago
        So you're saying they'd end up in the same ballpark? In that case, I'd rather have RISC-V's programming model.
        monocasa 3y ago
deleted 3y ago
[deleted]
utensil4778 3y ago
A lot of cheap USB1/2 widgets are actually a 6800 core. It's crazy how these old CPUs have stuck around for so long

ddingus 3y ago

There is a ton of code out there for pretty much any task you want. I have the 16 bit successor, the 65816, on a variable speed expansion card in my Apple 2. I run it in 8 bit mode most of the time mostly because it works and most library code is 8 bit. At those speeds, the chip is fast! Especially when one considers the simple model: ram clocked 1:1 with the cpu. In my case, I can run code over the 1Mhz bus, essentially turning most multi cycle ops into a single bus cycle per memory fetch. Or, the card has a megabyte of RAM and that runs at CPU speed. (0.15 to 16 Mhz) When doing that, it is fast enough to run large programs, written in higher level languages, at a useful speed. Of course Assembly language is crazy fast. It is a pretty fun environment to hack around in.