In 2000, someone gave me a 386 desktop that they were about to throw out, and I ran OpenBSD on it until 2005 or so. (I was a student, so getting new hardware was more of a big deal then.) To get it working I had to recompile the kernel (which I did on a "more capable" Celeron 366) without support for newfangled hardware such as USB and PCI in order to have enough memory to boot and log in in a tolerable amount of time. (Otherwise too painful due to swap.)
So I was pretty grateful at the time that it was still working, even though what I was doing was, now I can say with the benefit of hindsight, pretty crazy.
I ran a diskless 386DX 33mhz in my bedroom for many years, because it didn't make any noise. It ran a cut-down Linux distribution based on slackware, and I used it as a terminal and for small programming tasks.
I also kept it around for sentimental reasons, as it was the machine I did most of my early coding on. It didn't feel right to throw it out.
So thanks, Linux, for supporting my old junk hardware as long as you did! And congrats on losing ~400 lines of crufty code.
Celerons of that era were very easy to officially overclock generally because a great many of them were underclocked by Intel.
They ended up with far more of the more expensive 400+MHz capable parts than they expected to produce (presumably they were overly cautious when predicting how well the production process would work and therefor how many of the better rates chips thye'd get) but too few of the cheaper 300Mhz and 333MHz rated parts that were actually selling well - so they rebadged faster units as slower ones to fufil sales promises for the slower units.
This meant buying a machine based around a Celeron 300 or 333 (often referred to as "Silly-rons" at the time) was a lottery: you might have got one that is genuaninely expected not to be stable if run much faster, or you might have got one that Intel could have sold as a 450+MHz device.
As a side effect, those chips also helped launch Internet publishing - sites like the improbable Toms's Hardware, founded by a German M.D. if memory serves, cut their teeth on overclocking advice and benchmarks.
It wasn't so much as they were underclocked, but that Intel's process was so refined that they were often produced over-spec.
The other thing that made them so easy to over-clock was that, unlike the Pentium Pro, II and III, there was no on-chip L2 cache that would malfunction at higher speeds. All you were over-clocking was the CPU.
I had a dual-Celeron system that ran like a champ for the better part of ten years.
The binning process where higher end CPUs are marketed as lower end parts has been going on forever.
Only the first generation Celerons (which everyone hated) had no L2 cache. The second generation had 128KB of full-speed on-chip cache, which is actually why it overclocked well. The Pentium II and early Pentium III had 512KB of half-speed off-chip cache which struggled to keep up with the CPU when overclocking.
I still have an 8088 with a color display, dot matrix printer, math coprocessor, maxed out RAM (64 KB? I don't even remember) and a 10 MB hard drive + dual disk drives.
640KB was the max RAM. My first PC was the same configuration, except I had a 32MB drive. Oh! And towards the end I had both a CGA and Hercules card so I could have two screens.
It looks like the model 5150 didn't come with a hard disk, and the only official support for that was through the IBM 5161 Expansion Chassis. I think the author would have commented having an external drive for a PC, so I think it's safe to assume at least an XT equivalent.
(I've been searching for images of the chassis but to no success. I've never seen one, nor heard of it before today.)
And in the other direction, a PC Jr (also an 8088) maxed out at 128 KB, according to my references, though Wikipedia says there were third-party extensions to 736K. In any case, the Jr doesn't support the 8087 math coprocessor, so that's not what the author has.
It says it's a 5160 on the back by the power supply. The HD is, in fact, internal. And there's a phone jack on a card in back that looks newer than the rest, so it might have some kind of modem, though I have no idea how fast that is.
I also have no idea if it still works. It was covered in quite a bit of dust and I wonder if the HD won't be stuck after all this time.
I had a PC jr. The base model, which I had, came with 128k of memory, a single 5.25" inch floppy, and 2 cartridge slots. I booted DOS via a cartridge. There was an expansion unit you could purchase which had a 2nd floppy (very handy!) and I think it expanded max memory to 640k (but might have only been 256k).
So I was pretty grateful at the time that it was still working, even though what I was doing was, now I can say with the benefit of hindsight, pretty crazy.