7 ms·

The world's slowest Linux PC

102 points by kudu 12y ago

elinchrome 12y ago
How do you emulate a 32 bit CPU with only eight bits? Seems like you'd have to quadruple everything and then flatten it again after.
- wirelessest 12y ago
  Sounds like that's exactly what he did.
- danbruc 12y ago
  This is actually pretty common. There was a time when not every CPU had a FPU and floating point operations were emulated in software if required. Or doing 64 bit integer operations on a 32 bit CPU. Or doing arbitrary precision arithmetics on todays CPUs. You do it just like in school, piece by piece, but instead of single digits you use the largest registers available. If you really like it slow you could of course also just use plain strings to represent numbers and do all math on a char by char, digit by digit basis.
- wtallis 12y ago
  There used to be bit-slice processors that chained together narrow (eg. 4-bit) chips to build a wider processor. This is pretty much a software emulation of that technique, but lacking the parallelism. https://en.wikipedia.org/wiki/Bit_slicing https://en.wikipedia.org/wiki/Bit_slicing
- xxs 12y ago
  The simple answer would be: by using memory. More bits means that the CPU can operate at larger amounts of data at once. For example shift would need to perform multiple 8bit operations but it's entirely doable (I hope the cpu he used has shifts with the carry flag)
- hga 12y ago
  Adding to some of these other comments, when IBM did their groundbreaking 32 bit System/360 in the 1960's, they started with a nice silicon transistor based logic family, but it pretty much ran at only one speed. So to deliver a family of computers with the same ISA, they microcoded the slower ones. The very slowest one had 8 bit wide execution units, and presumably used similar techniques to deliver its 32 bit macroarchitecture. Per Wikipedia (https://en.wikipedia.org/wiki/IBM_System/360 https://en.wikipedia.org/wiki/IBM_System/360), the Model 30 in 1965 could execute "up to" 34,500 instructions per second, the hardwired Model 75 could do about a million. See e.g.: https://en.wikipedia.org/wiki/IBM_System/360#Table_of_System.2F360_models https://en.wikipedia.org/wiki/IBM_System/360#Table_of_System...
- boomlinde 12y ago
  Commonly, to perform something like an arbitrary width addition, these CPUs have a carry flag that is set if an operation overloads, so that the carry can be added into the next addition. This way you can simply chain simple 8-bit additions to get the desired operation width. For example, a 16-bit addition (0x5555 + 0x1234 on 6502 clc lda a adc b sta res lda a+1 adc b+1 sta res+1 a: .byte $55, $55 b: .byte $34, $12 res: .byte $00, $00 ; reserved for result
kyberias 12y ago
This horribly nonnovel.
- danellis 12y ago
  Can you point me to the other ones for comparison?
  - deleted 12y ago
    [deleted]
  - kyberias 12y ago
    There is an infinite number of ways to run Linux slowly by emulating compatible processors (here ARM) on slow HW.
parski 12y ago
How I would dread debugging this machine.
- ansible 12y ago
  The main thing is to get the ARM instructions working correctly, so that's not too bad. If all of those are correct, it should boot and do basic stuff. The next bit of work is to get the peripherals going.
voltagex_ 12y ago
Previously: https://news.ycombinator.com/item?id=8791812 https://news.ycombinator.com/item?id=8791812, https://news.ycombinator.com/item?id=5581851 https://news.ycombinator.com/item?id=5581851
- jared314 12y ago
  More Previously: https://news.ycombinator.com/item?id=3767410 https://news.ycombinator.com/item?id=3767410 (1054 days ago)
  - voltagex_ 12y ago
    Thanks. I wonder if I can automate that - although HN bans bots, right?
    - jared314 12y ago
      Just add it to one of the many HN browser extensions. The tough part is correlating the different urls and titles while filtering out the irrelevant comments from past discussions. I don't just want to know that this is an old story (I can figure that out), or that it's a "cool project" that a commenter might use sometime soon, 5 years ago. I want to know what the informed comments were at that time. Was it important in that time period? What were the concerns at the time? Did they abandon the idea? Why?
ChuckMcM 12y ago
While I agree it is not novel at all [1] it is a useful exercise for someone to do and it especially reinforces the notion that Turing discussed with respect to computability. For a long time (and possibly even today) every IBM mainframe could emulate (at speed or faster) all previous versions of their mainframe line such that the investment in software was preserved. [1] I did a PDP-11 emulator on the Arduino with FRAM chips for 'core' which was made quite a bit easier by the existence of PDP-11 instruction set diagnostics, and other test software which validated the CPU was running "correctly".
swatow 12y ago
Somehow the fact that this was accomplished by emulating a 32 bit processor with an 8 bit processor, made this less appealing to me. I'm sure it was technically very challenging, but I would have been more excited to see Linux somehow running natively on the processor. I wonder what the slowest processors running Linux natively are?
- andrewchambers 12y ago
  Almost certainly one of thing things supported by http://www.uclinux.org/ http://www.uclinux.org/.
- JoshTriplett 12y ago
  For x86, older versions of Linux ran on a 386, but current versions require a 486, or a Pentium if you turn on stack protection (as most distro kernels do). (Almost nobody noticed.) However, drivers for ISA and similar still exist in the kernel, so you could likely get the most recent kernel running on a real 486, if you had one around. The slowest systems still running Linux, though, are probably those running the m68k port. Many people doing development for that port use m68k emulators, which run many times faster than the fastest available hardware. However, at least in theory, you can run the m68k port on any m68k processor that has an MMU.
  - Starwatcher2001 12y ago
    Can't comment on Linux, but we used to run Xenix on a 286.
  - ansible 12y ago
    And you can run uCLinux on the m68k processors that don't have an MMU. I was using it for a Motorola Dragonball microcontroller... 14 years ago.
jrockway 12y ago
"Calibrating delay loop... 58.77 BogoMIPS" As a comparison, from my i7-4771 @ 3.5GHz: smpboot: Total of 8 processors activated (55999.93 BogoMIPS) Computers sure are fast these days. Too bad we write such slow software for them.
- iso8859-1 12y ago
  Except if you emulate them in JavaScript. I get 5.10 BogoMIPS: http://copy.sh/v86/?profile=custom&cdrom.url=http://k%C3%A6n.guru/files/ttylinux-pc_i486-2015.01.iso http://copy.sh/v86/?profile=custom&cdrom.url=http://k%C3%A6n...
  - plaguuuuuu 12y ago
    Probably also get a low BogoMIPS score if you boot up an image with a web browser, then run javascript emulation inside the javascript emulation.
  - Maakuth 12y ago
    The bogomips is a really bad estimate of performance (hence 'bogo'). There's considerable difference in the bogomips calculation even between different ARM subarchitectures. There was a good article about the issue recently in LWN: http://lwn.net/Articles/628531/ http://lwn.net/Articles/628531/
boyter 12y ago
Interesting, but I found this effort http://www.homebrewcpu.com/ http://www.homebrewcpu.com/ more impressive overall. It quite literally is a home made CPU which then had Minix 2 ported to it and booted. A very impressive achievement.
- stas12 12y ago
  Thanks for this link. It deserves a separate thread!
- code_duck 12y ago
  Neat article! I love the box he put it in. The neatly labeled sections are somewhat fascinating and give interesting insight into how a CPU works. Things seem different when your CPU is a foot long and sits on the table I suppose...
stragulus 12y ago
This reminds me of the dial-in server I built in our student home back in '97-'98. It was a 386sx 16Mhz with 2MB of memory and a 40MB hard drive that you had to preheat in the oven or it wouldn't spin up. That was realistically the lowest spec'd hardware you could actually get to run linux on. It took half an hour to boot, but that was okay since it was always on anyway. It took about 5 minutes to set up a ppp connection using a dial-in modem, and then the whole house had internet access through its network adapter. Unless someone had tripped over the coax cables again of course..
- pjmlp 12y ago
  I had one when they were pretty new, back in 1991. Had MS-DOS reduced to the minimum, jumping into Windows 3.1 straight after booting and using Stacker to be able to double the hard disc contents. By the time I came to use GNU/Linux, I was already on Pentium 75 Mhz and never imagine such 386sx would ever manage it.

102 points by kudu 12y ago

How do you emulate a 32 bit CPU with only eight bits? Seems like you'd have to quadruple everything and then flatten it again after.

wirelessest 12y ago
Sounds like that's exactly what he did.
danbruc 12y ago
This is actually pretty common. There was a time when not every CPU had a FPU and floating point operations were emulated in software if required. Or doing 64 bit integer operations on a 32 bit CPU. Or doing arbitrary precision arithmetics on todays CPUs. You do it just like in school, piece by piece, but instead of single digits you use the largest registers available. If you really like it slow you could of course also just use plain strings to represent numbers and do all math on a char by char, digit by digit basis.
wtallis 12y ago
There used to be bit-slice processors that chained together narrow (eg. 4-bit) chips to build a wider processor. This is pretty much a software emulation of that technique, but lacking the parallelism. https://en.wikipedia.org/wiki/Bit_slicing https://en.wikipedia.org/wiki/Bit_slicing
xxs 12y ago
The simple answer would be: by using memory. More bits means that the CPU can operate at larger amounts of data at once. For example shift would need to perform multiple 8bit operations but it's entirely doable (I hope the cpu he used has shifts with the carry flag)
hga 12y ago
Adding to some of these other comments, when IBM did their groundbreaking 32 bit System/360 in the 1960's, they started with a nice silicon transistor based logic family, but it pretty much ran at only one speed. So to deliver a family of computers with the same ISA, they microcoded the slower ones. The very slowest one had 8 bit wide execution units, and presumably used similar techniques to deliver its 32 bit macroarchitecture. Per Wikipedia (https://en.wikipedia.org/wiki/IBM_System/360 https://en.wikipedia.org/wiki/IBM_System/360), the Model 30 in 1965 could execute "up to" 34,500 instructions per second, the hardwired Model 75 could do about a million. See e.g.: https://en.wikipedia.org/wiki/IBM_System/360#Table_of_System.2F360_models https://en.wikipedia.org/wiki/IBM_System/360#Table_of_System...
boomlinde 12y ago
Commonly, to perform something like an arbitrary width addition, these CPUs have a carry flag that is set if an operation overloads, so that the carry can be added into the next addition. This way you can simply chain simple 8-bit additions to get the desired operation width. For example, a 16-bit addition (0x5555 + 0x1234 on 6502 clc lda a adc b sta res lda a+1 adc b+1 sta res+1 a: .byte $55, $55 b: .byte $34, $12 res: .byte $00, $00 ; reserved for result

kyberias 12y ago

This horribly nonnovel.

danellis 12y ago
Can you point me to the other ones for comparison?
- deleted 12y ago
  [deleted]
- kyberias 12y ago
  There is an infinite number of ways to run Linux slowly by emulating compatible processors (here ARM) on slow HW.

parski 12y ago

How I would dread debugging this machine.

ansible 12y ago
The main thing is to get the ARM instructions working correctly, so that's not too bad. If all of those are correct, it should boot and do basic stuff. The next bit of work is to get the peripherals going.

voltagex_ 12y ago

Previously: https://news.ycombinator.com/item?id=8791812 https://news.ycombinator.com/item?id=8791812, https://news.ycombinator.com/item?id=5581851 https://news.ycombinator.com/item?id=5581851

jared314 12y ago
More Previously: https://news.ycombinator.com/item?id=3767410 https://news.ycombinator.com/item?id=3767410 (1054 days ago)
- voltagex_ 12y ago
  Thanks. I wonder if I can automate that - although HN bans bots, right?
  - jared314 12y ago
    Just add it to one of the many HN browser extensions. The tough part is correlating the different urls and titles while filtering out the irrelevant comments from past discussions. I don't just want to know that this is an old story (I can figure that out), or that it's a "cool project" that a commenter might use sometime soon, 5 years ago. I want to know what the informed comments were at that time. Was it important in that time period? What were the concerns at the time? Did they abandon the idea? Why?

ChuckMcM 12y ago

While I agree it is not novel at all [1] it is a useful exercise for someone to do and it especially reinforces the notion that Turing discussed with respect to computability. For a long time (and possibly even today) every IBM mainframe could emulate (at speed or faster) all previous versions of their mainframe line such that the investment in software was preserved. [1] I did a PDP-11 emulator on the Arduino with FRAM chips for 'core' which was made quite a bit easier by the existence of PDP-11 instruction set diagnostics, and other test software which validated the CPU was running "correctly".

swatow 12y ago

Somehow the fact that this was accomplished by emulating a 32 bit processor with an 8 bit processor, made this less appealing to me. I'm sure it was technically very challenging, but I would have been more excited to see Linux somehow running natively on the processor. I wonder what the slowest processors running Linux natively are?

andrewchambers 12y ago
Almost certainly one of thing things supported by http://www.uclinux.org/ http://www.uclinux.org/.
JoshTriplett 12y ago
For x86, older versions of Linux ran on a 386, but current versions require a 486, or a Pentium if you turn on stack protection (as most distro kernels do). (Almost nobody noticed.) However, drivers for ISA and similar still exist in the kernel, so you could likely get the most recent kernel running on a real 486, if you had one around. The slowest systems still running Linux, though, are probably those running the m68k port. Many people doing development for that port use m68k emulators, which run many times faster than the fastest available hardware. However, at least in theory, you can run the m68k port on any m68k processor that has an MMU.
- Starwatcher2001 12y ago
  Can't comment on Linux, but we used to run Xenix on a 286.
- ansible 12y ago
  And you can run uCLinux on the m68k processors that don't have an MMU. I was using it for a Motorola Dragonball microcontroller... 14 years ago.

jrockway 12y ago

"Calibrating delay loop... 58.77 BogoMIPS" As a comparison, from my i7-4771 @ 3.5GHz: smpboot: Total of 8 processors activated (55999.93 BogoMIPS) Computers sure are fast these days. Too bad we write such slow software for them.

iso8859-1 12y ago
Except if you emulate them in JavaScript. I get 5.10 BogoMIPS: http://copy.sh/v86/?profile=custom&cdrom.url=http://k%C3%A6n.guru/files/ttylinux-pc_i486-2015.01.iso http://copy.sh/v86/?profile=custom&cdrom.url=http://k%C3%A6n...
- plaguuuuuu 12y ago
  Probably also get a low BogoMIPS score if you boot up an image with a web browser, then run javascript emulation inside the javascript emulation.
- Maakuth 12y ago
  The bogomips is a really bad estimate of performance (hence 'bogo'). There's considerable difference in the bogomips calculation even between different ARM subarchitectures. There was a good article about the issue recently in LWN: http://lwn.net/Articles/628531/ http://lwn.net/Articles/628531/

boyter 12y ago

Interesting, but I found this effort http://www.homebrewcpu.com/ http://www.homebrewcpu.com/ more impressive overall. It quite literally is a home made CPU which then had Minix 2 ported to it and booted. A very impressive achievement.

stas12 12y ago
Thanks for this link. It deserves a separate thread!
code_duck 12y ago
Neat article! I love the box he put it in. The neatly labeled sections are somewhat fascinating and give interesting insight into how a CPU works. Things seem different when your CPU is a foot long and sits on the table I suppose...

stragulus 12y ago

This reminds me of the dial-in server I built in our student home back in '97-'98. It was a 386sx 16Mhz with 2MB of memory and a 40MB hard drive that you had to preheat in the oven or it wouldn't spin up. That was realistically the lowest spec'd hardware you could actually get to run linux on. It took half an hour to boot, but that was okay since it was always on anyway. It took about 5 minutes to set up a ppp connection using a dial-in modem, and then the whole house had internet access through its network adapter. Unless someone had tripped over the coax cables again of course..

pjmlp 12y ago
I had one when they were pretty new, back in 1991. Had MS-DOS reduced to the minimum, jumping into Windows 3.1 straight after booting and using Stacker to be able to double the hard disc contents. By the time I came to use GNU/Linux, I was already on Pentium 75 Mhz and never imagine such 386sx would ever manage it.