I've recently commenced revitalizing a very old PC. She's running an Intel Pentium, x86_64. I thought I'd give Gentoo a go because I've found it very appealing and as a Bedrock user I wanted to be able to boot off of Gentoo's init system (initrc, we all know why) as well as bootloader. I've gotten almost halfway through the install ( maybe more like a third :))) ), and now I'm looking for the stage3 files for my PC. I've noticed that though there are builds for i486 and i686. Being genuinely interested in which my PC was, I searched it up and after some light digging found this explanation:

  • i386 works with any x86 processor (Intel, AMD,etc.),
  • i486 has some performance tun[n]ing.
  • i586 for Pentium and Pentium-MMX
  • i686 for Pentium-Pro, P2,P3, P4, etc.


But in that case Gentoo doesn't support my device?!? Hence, my question: what i version (?) is my Intel Pentium PC? And where are the stage3 files for it? Is it possible to use, say, an i486 for a presumed i586?

Thanks in advance, bobbbay

P.S.: PC is the ol' HP Pavilion Slim.

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    "Very old"? Look at the on topic questions on this site, then you will know what is "very old" 😉 – OmarL Jul 15 at 6:17
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    The machine linked is less than 7 years old, as G2020 was introduced in 2013. It features an up to date AMD64 ISA, way beyond everything mentioned and capable to run any modern version of any OS. You might rather want to ask in Unix.SE than here. – Raffzahn Jul 15 at 10:24

The original Pentium, which succeeded the i80486, was indeed the original definition of the i586 instruction set - and not x86_64. But the Pentium was introduced in 1993, and your HP machine is much newer than that. Intel has continued to use the Pentium brand for almost every x86-compatible CPU line they've made since then, to great confusion among people not intimately familiar with the history.

The Pentium G-series does support x86_64, and is really too new to ask the Retrocomputing SE about. I will simply recommend you to install the amd64 version of Gentoo rather than the i586 or i686 builds.

For anyone who actually has a Pentium Classic, Pentium-MMX, or other genuine i586 device, Gentoo doesn't have an i586 stage build, but the i486 build will work. You can then rebuild it optimised for i586 and the specific CPU that you have. Expect it to take some time, on the order of weeks, as these CPUs are very old and slow.

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  • Ah. Well, thanks, but that sucks for me :))) I already used the x86 "minimal" ISO for my boot USB. I'm guessing I'd have to completely redo with the different ISO? Or could I continue on but using the amd64 stage3 files? Thanks! – Bobbay Jul 15 at 3:36
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    @Bobbay The amd64 userspace requires both an amd64 CPU and an amd64 kernel. However, you should be able to use the same disk partitions and filesystem format. – Chromatix Jul 15 at 5:40
  • I don't think that blindly installing amd64 is always a good idea. For memory-limited systems i386 is definitely less memory-hungry, Also there exist programs that do work faster in i386 flavour than in amd64. – lvd Jul 15 at 6:30
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    @lvd It's unlikely to have less than 1GB installed, which is what I'd call "memory limited". The OP clearly doesn't have any niche use case in mind, or they'd have done more research beforehand. A 64-bit OS is always a good match for 64-bit hardware, especially in the case of AMD64 versus x86. – Chromatix Jul 15 at 7:21
  • "Expect it to take some time" True. Then again distcc is a great help to those emerging/compiling stuff for slower processors. It is well integrated with the Gentoo build process and can be used early on. So booting the premade i486 and optimize later on isn't much differnt from doing so on the fastest machine one owns. – Raffzahn Jul 19 at 14:51

Gentoo is a source-based distribution, where everything is built from the source. You can tune GCC to build for i586 like this:

COMMON_FLAGS="-march=i586 -mtune=pentium -O2 -pipe"

in your /etc/portage/make.conf

Changing -O2 to -Os will decrease executables size a bit.

Another thing you need to worry is to build correct kernel.

If the build process is failing or slow on your device, you can try building everything in a virtual machine on a modern pc, then transfer image to the device.

To know what CPU you do have, find any bootable 'live' linux distribution (that is able to boot on your old pc, this for example http://tinycorelinux.net/) and then type cat /proc/cpuinfo. You can try to use this tiny linux as a chroot base system for your gentoo, as well.

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