3 ms·

So it's possible to run Linux on any 8 bit CPU?

by DeathArrow 2y ago

guenthert 2y ago
The MC68008 has an external 8bit data bus. Internal registers are 32bit wide. Typically one means CPUs with 8bit wide registers when one talks about a 8bit CPU, e.g. 6502, 8080 etc. The Linux kernel requires a MMU for virtual memory support. Here a severly stripped-down version, μClinux, is used which doesn't support virtual memory and (hence) doesn't require a MMU, so any CPU with a 32bit linear address space (implying 32bit wide address registers) could be supported. At the very least a C compiler (supporting GNU extensions) for that CPU is needed. Said that, there is ELKS (a subset of Linux functionality for 8086) and there is even a (memory-enhanced) C64 running a Linux VM (very, very slowly though).
- DeathArrow 2y ago
  My bad, I thought registers are 8 bit wide in MC68008. What you are saying totally makes sense.
- nopakos 2y ago
  So, a Unix running on a Sinclair QL, which is based on 68008 would be possible, theoretically!
  - bitwize 2y ago
    That was Linus's first computer! I wonder if he'd be interested in writing such a kernel, to revisit an old friend...
deleted 2y ago
[deleted]
RetroTechie 2y ago
You could, if you'd emulate a 32b cpu on that 8-bitter. The real limitation here is memory. Imho it says a lot about modern day software bloat that even an ancient 2.0 series kernel needs ~600KB (ROM/RAM combined). For what, really? That's already a lot of features & almost all hw drivers stripped from it, right? What's that remaining ~600KB code+data doing then?
- szundi 2y ago
  640kb “should be enough for everyone”
- nxobject 2y ago
  I would be remiss if I didn’t post this classic hack - Linux running on an ATmega via emulation, bit-banging a DIMM directly. [1] [1] https://dmitry.gr/?r=05.Projects&proj=07.%20Linux%20on%208bit https://dmitry.gr/?r=05.Projects&proj=07.%20Linux%20on%208bi...

3 ms·

So it's possible to run Linux on any 8 bit CPU?

by DeathArrow 2y ago

So it's possible to run Linux on any 8 bit CPU?

guenthert 2y ago
The MC68008 has an external 8bit data bus. Internal registers are 32bit wide. Typically one means CPUs with 8bit wide registers when one talks about a 8bit CPU, e.g. 6502, 8080 etc. The Linux kernel requires a MMU for virtual memory support. Here a severly stripped-down version, μClinux, is used which doesn't support virtual memory and (hence) doesn't require a MMU, so any CPU with a 32bit linear address space (implying 32bit wide address registers) could be supported. At the very least a C compiler (supporting GNU extensions) for that CPU is needed. Said that, there is ELKS (a subset of Linux functionality for 8086) and there is even a (memory-enhanced) C64 running a Linux VM (very, very slowly though).
- DeathArrow 2y ago
  My bad, I thought registers are 8 bit wide in MC68008. What you are saying totally makes sense.
- nopakos 2y ago
  So, a Unix running on a Sinclair QL, which is based on 68008 would be possible, theoretically!
  - bitwize 2y ago
    That was Linus's first computer! I wonder if he'd be interested in writing such a kernel, to revisit an old friend...
deleted 2y ago
[deleted]
RetroTechie 2y ago
You could, if you'd emulate a 32b cpu on that 8-bitter. The real limitation here is memory. Imho it says a lot about modern day software bloat that even an ancient 2.0 series kernel needs ~600KB (ROM/RAM combined). For what, really? That's already a lot of features & almost all hw drivers stripped from it, right? What's that remaining ~600KB code+data doing then?
- szundi 2y ago
  640kb “should be enough for everyone”
- nxobject 2y ago
  I would be remiss if I didn’t post this classic hack - Linux running on an ATmega via emulation, bit-banging a DIMM directly. [1] [1] https://dmitry.gr/?r=05.Projects&proj=07.%20Linux%20on%208bit https://dmitry.gr/?r=05.Projects&proj=07.%20Linux%20on%208bi...