9 ms·

I think you deeply underestimate embedded use. There are a huge number of devices running on relatively obscure microarchitectures.

duskwuff 6y ago
68k is basically dead in embedded. Most of the parts have been out of production for many years, and the ones that remain are only used for legacy applications -- they're 5V parts, making them incompatible with most newer components, and they're completely outclassed by ARM microcontrollers.
- tgb 6y ago
  As a curious ignorant - what's used now instead of 5V? Why was there a transition away from 5V? I'm assuming this means 5 volts and not something more arcane.
  - mumblemumble 6y ago
    3.3V seems to be where everything is going in the hobbyist space. If your device is powered by batteries, 3.3V will let you get longer battery life than 5V. I think I recall hearing that 3.3V can reduce power consumption by as much as 50% relative to 5V. If your device is powered by USB, which is nominally 5V, 3.3V can still be nice because USB power supplies don't always supply the cleanest power, so regulating it down to 3.3V can result in a more reliable power supply.
  - wongarsu 6y ago
    Most microcontrollers moved to 3.3V, or even 1.8V. Some of them have some 5V tolerant ports to communicate with 5V devices, but for the most part embedded now runs on and communicates over 3.3V. The reason is mostly power efficiency and the option for higher frequencies as far as I'm aware
  - tssva 6y ago
    3.3v and 1.2v are probably the most common these days but there are other voltages in use. Lower power usage, less heat and smaller packaging are the main drivers for lower voltages.
  - Someone 6y ago
    Power usage is proportional to the square of the voltage. So, you want to keep the voltage low for battery life or to prevent your CPU from overheating. Lower voltages also make transistors slower, though. That can be offset by making them smaller, but we couldn’t do that decades ago (https://electronics.stackexchange.com/questions/109533/why-a-lower-voltage-is-better-for-modern-fast-cpu-and-other-similar-chips https://electronics.stackexchange.com/questions/109533/why-a..., https://en.wikipedia.org/wiki/CPU_core_voltage#Power_saving_and_clock_speed https://en.wikipedia.org/wiki/CPU_core_voltage#Power_saving_...) I guess there also is some effect along the lines “higher voltages decrease sensitivity to noise” that prevented early designs from using lower voltages and lower currents. As to what’s used now: 3.3V was the new 5V, but state of the art CPUs are even lower at ≈1.2V
  - phire 6y ago
    Modern stuff used as little voltage as possible. We are taking under 1v at times for silicon core voltage. They also use VRMs to dynamically adjust voltage depending on load. These days, IO voltage is usually detached from core voltage, and there may actually be multiple IO voltages. Memory and PCIe often get their own carefully turned IO voltages. For lower speed, low cost devices, 3.3v is basically standardized, though on battery powered devices you will commonly see 1.8v. Anything hobbyist is being dragged to 3.3v. 5v devices keep getting harder and harder to find.
  - pantalaimon 6y ago
    3.3V
- roywashere 6y ago
  ARM and a little bit of MIPS and maybe some RISC-V in the future!
- phire 6y ago
  I was actually looking into this last week. All original 68k CPUs appeared to be well beyond end of life and the only source appeared recycled chips from China. But there are modern NXP coldfire parts. The CPU core is mostly binary compatible with 68k, just with some legacy instructions removed. Coldfire SOCs clock up to about 400mhz and have support for modern devices like ethernet and usb.
  - duskwuff 6y ago
    You can still get new 68SEC000s from NXP, but the part is NRND (not recommended for new designs), so you'd better order soon if you're interested. Ironically, a HN comment I made about this a few years ago is now one of the top Google results for "68SEC000", ranking higher than NXP's own product page.
    - phire 6y ago
      Oh right... I think I ran into your comment while researching. Mouser didn't appear to have any, so I decided it must have gone out of stock in the last few years. Though now I see digikey still have them. Are they actually still sold by NXP, or do digikey just have one last shipment sitting in a warehouse?
      - duskwuff 6y ago
        NXP doesn't sell direct to consumers. Their site doesn't list the part as discontinued, though, so I'd assume that NXP still have some stock of the part. (How old that stock is, on the other hand, is a good question. I wouldn't be surprised if it's many years old.)
    - snvzz 6y ago
      It's a shame getting 68010s is not as easy. 68010 is IMO a bugfixed 68k, and what should have been used for any design that would otherwise target 68k, since the moment it became available.
      - fredoralive 6y ago
- snvzz 6y ago
  3.3v 68Ks could be made available. They do exist in the form of M683XX microcontrollers.
- cmrdporcupine 6y ago
  Coldfire is not dead, though it's going that way. There's plenty of network hardware etc. based around it. I didn't make it through the whole 68k/LLVM presentation when it came out earlier this week but I would imagine the same compiler backend will be used for the Coldfire ISA.
loeg 6y ago
OP is talking about FreeBSD, and the only "obscure" embedded microarchitectures FreeBSD supports that he did not mention are 32-bit ARM, MIPS, PPC, and RISCV.
pabs3 6y ago
Even relatively common devices have obscure architectures in them, an example of this is that Allwinner ARM CPUs have an OpenRISC core for power management: https://linux-sunxi.org/AR100 https://linux-sunxi.org/AR100

duskwuff 6y ago

68k is basically dead in embedded. Most of the parts have been out of production for many years, and the ones that remain are only used for legacy applications -- they're 5V parts, making them incompatible with most newer components, and they're completely outclassed by ARM microcontrollers.

tgb 6y ago
As a curious ignorant - what's used now instead of 5V? Why was there a transition away from 5V? I'm assuming this means 5 volts and not something more arcane.
- mumblemumble 6y ago
  3.3V seems to be where everything is going in the hobbyist space. If your device is powered by batteries, 3.3V will let you get longer battery life than 5V. I think I recall hearing that 3.3V can reduce power consumption by as much as 50% relative to 5V. If your device is powered by USB, which is nominally 5V, 3.3V can still be nice because USB power supplies don't always supply the cleanest power, so regulating it down to 3.3V can result in a more reliable power supply.
- wongarsu 6y ago
  Most microcontrollers moved to 3.3V, or even 1.8V. Some of them have some 5V tolerant ports to communicate with 5V devices, but for the most part embedded now runs on and communicates over 3.3V. The reason is mostly power efficiency and the option for higher frequencies as far as I'm aware
- tssva 6y ago
  3.3v and 1.2v are probably the most common these days but there are other voltages in use. Lower power usage, less heat and smaller packaging are the main drivers for lower voltages.
- Someone 6y ago
  Power usage is proportional to the square of the voltage. So, you want to keep the voltage low for battery life or to prevent your CPU from overheating. Lower voltages also make transistors slower, though. That can be offset by making them smaller, but we couldn’t do that decades ago (https://electronics.stackexchange.com/questions/109533/why-a-lower-voltage-is-better-for-modern-fast-cpu-and-other-similar-chips https://electronics.stackexchange.com/questions/109533/why-a..., https://en.wikipedia.org/wiki/CPU_core_voltage#Power_saving_and_clock_speed https://en.wikipedia.org/wiki/CPU_core_voltage#Power_saving_...) I guess there also is some effect along the lines “higher voltages decrease sensitivity to noise” that prevented early designs from using lower voltages and lower currents. As to what’s used now: 3.3V was the new 5V, but state of the art CPUs are even lower at ≈1.2V
- phire 6y ago
  Modern stuff used as little voltage as possible. We are taking under 1v at times for silicon core voltage. They also use VRMs to dynamically adjust voltage depending on load. These days, IO voltage is usually detached from core voltage, and there may actually be multiple IO voltages. Memory and PCIe often get their own carefully turned IO voltages. For lower speed, low cost devices, 3.3v is basically standardized, though on battery powered devices you will commonly see 1.8v. Anything hobbyist is being dragged to 3.3v. 5v devices keep getting harder and harder to find.
- pantalaimon 6y ago
  3.3V
roywashere 6y ago
ARM and a little bit of MIPS and maybe some RISC-V in the future!
phire 6y ago
I was actually looking into this last week. All original 68k CPUs appeared to be well beyond end of life and the only source appeared recycled chips from China. But there are modern NXP coldfire parts. The CPU core is mostly binary compatible with 68k, just with some legacy instructions removed. Coldfire SOCs clock up to about 400mhz and have support for modern devices like ethernet and usb.
- duskwuff 6y ago
  You can still get new 68SEC000s from NXP, but the part is NRND (not recommended for new designs), so you'd better order soon if you're interested. Ironically, a HN comment I made about this a few years ago is now one of the top Google results for "68SEC000", ranking higher than NXP's own product page.
  - phire 6y ago
    Oh right... I think I ran into your comment while researching. Mouser didn't appear to have any, so I decided it must have gone out of stock in the last few years. Though now I see digikey still have them. Are they actually still sold by NXP, or do digikey just have one last shipment sitting in a warehouse?
    - duskwuff 6y ago
      NXP doesn't sell direct to consumers. Their site doesn't list the part as discontinued, though, so I'd assume that NXP still have some stock of the part. (How old that stock is, on the other hand, is a good question. I wouldn't be surprised if it's many years old.)
  - snvzz 6y ago
    It's a shame getting 68010s is not as easy. 68010 is IMO a bugfixed 68k, and what should have been used for any design that would otherwise target 68k, since the moment it became available.
    - fredoralive 6y ago
snvzz 6y ago
3.3v 68Ks could be made available. They do exist in the form of M683XX microcontrollers.
cmrdporcupine 6y ago
Coldfire is not dead, though it's going that way. There's plenty of network hardware etc. based around it. I didn't make it through the whole 68k/LLVM presentation when it came out earlier this week but I would imagine the same compiler backend will be used for the Coldfire ISA.

loeg 6y ago

OP is talking about FreeBSD, and the only "obscure" embedded microarchitectures FreeBSD supports that he did not mention are 32-bit ARM, MIPS, PPC, and RISCV.

pabs3 6y ago

Even relatively common devices have obscure architectures in them, an example of this is that Allwinner ARM CPUs have an OpenRISC core for power management: https://linux-sunxi.org/AR100 https://linux-sunxi.org/AR100