It depends. IBM PC-DOS 4.x was better than MS-DOS 4.x.
Re: Worst cpus and worst computer builds

I'm not sure if MS-DOS 4.0 is very 'era-correct'... It was a very experimental version with multitasking support, quite buggy, it even has its own wiki page: https://en.wikipedia.org/wiki/MS-DOS_4.0_(multitasking)
I haven't actually seen MS-DOS 4.0 in the wild. I believe most machines were sold with DOS 3.x, until the manufacturers moved straight to 5.0.

I've only seen DOS 4.x installed on 286 computers. I guess that's not so bad, but not a good option.

I mean, if you've got a 8086 or even a 286, DOS 3.x runs better; if you've got a 386+, DOS 5 have better memory management. DOS 4 does not have the memory capabilities of DOS 5 nor the frugality of DOS 3.x so it's the best option.

Well I tried it out and the memory optimization is horrible. So I don't see much use in it. I installed DR-DOS 5.0 instead on my 1990 build and its amazing! It really is a great alternative to MS-DOS of the time.

Jo22 wrote:

It depends. IBM PC-DOS 4.x was better than MS-DOS 4.x.
Re: Worst cpus and worst computer builds

No, it's the other way around. Please don't mix up MS-DOS 4.01 (which was MS' fix-up of the broken IBM PC-DOS 4.00) with the crappy Multitasking MS-DOS 4.0 (aka European MS-DOS 4.0), which is way older and based on MS-DOS 2.0.

4.01 just took up more memory than 3.3 for no benefit most people could see, and then 5 came out with its fancy load everything high umb which made 4.01 look even worse. 4.01 was a stopgap dos that worked with larger partitions than 3.3 could (32mb max in dos3, dos4 let this go to 2gb or something).

is it worth trying? no. 3.3 or 5/6.22 is the bookends!

4.01 have the benefit to support larger hdds over 3.31 , then you are limited on 32MB partitions.
I think if you using an expended memory board, memory wouldnt be a problem i guess.

DOS 5.0 doesnt really make any sense of High memory stuff, it works different on an XT anyway.

I only would use 5.0 on a 286 class machine.

I changed my Schneider EuroPC (XT) from 3.3 to 4.01 in oder to use up to 2GB CF Partitions.
Booting from 2GB CF does not work, accessing did work. I changed the Booting drive to 128MB CF and everything is fine.
Msdos 4.x consumes more RAM and you have to use "share" in order to access the larger partitions (install within config.sys)
I have not chosen if I will stay on Dos4.01....