I think it was 3.3x where things started working. I don't recall 4.x being around much. I do remember 5 and 6. For some reason 4 never made a splash in my circle of friends.

4 was, TBH, appalling for its time.

It took more base memory than ever. It had a complicated code page system that most people didn't want, and a clunky early version of IBM DOSShell that was scorned although it grew into something useful.

But it supported disk partitions over 32MB, and for that reason, it was reluctantly adopted. If you had a 286 or 386, then there were measures that you could take with a memory manager to make it not so bad, but on 8088/8086 class hardware, it didn't leave enough free memory for many big apps to run.

IIRC 6.22 was the pinnacle of MS-DOS, with all the comfort and niceties one could expect at the time. Then began the Windows era.

I think the pinnacle goes to MS-DOS 7.1, which while bundled with Windows was also usable as a DOS by itself and contained features like FAT32 support. MS-DOS 8 was the last version that came with the ill-fated Windows Me and significantly neutered.

6.22 would likely be what I was remembering.

I had good memories of DR-DOS 5

I was kind of happy with MSDOS 2.11, I felt that they'd got the basics in place (in particular hard disk / subdirectory support) and that bloat hadn't started. From memory I used this for years and years although I was young so time didn't rush past so quickly so who really knows. I kept a version of MSDOS 2.11 debug.com around for decades (patched with itself so it wouldn't just do a version check then quit). From memory it was something like 12K bytes whereas debug.exe from MSDOS 6.x was more like 60K bytes.

> My brain is rusty

It is. Because:

> but I feel like MSDOS 5.11 was where things finally just worked

There was no MS-DOS 5.11.

It went 4, 4.01, 5, 6, 6.2, 6.21, 6.22.

IBM had a few extra versions as the divorce was occurring at the time.

> There was no MS-DOS 5.11.

There was Windows 3.11 which ran on top of MS-DOS 5.0, the two numbers probably got mixed in their memory.

There was also an MS-DOS 2.11.

There was indeed a Windows 3.11 and the much more common Windows for Workgroups 3.11 which was a profoundly different product (32-bit disk subsystem & 32-bit networking subsystem -- the first time these pillars of Win9x went out into the world.)

But neither of them ran on any particular version of DOS. They ran on PC DOS, MS-DOS and DR-DOS -- although Microsoft tried very hard to block the latter:

https://en.wikipedia.org/wiki/AARD_code

They ran on DOS 3.3, 4, 5, 6, and 7.

There's nothing at all that links them especially to MS-DOS 5.

Perhaps you mean DOS 5.0. If I remember well, DOS 6 wasn't different from DOS 5 internally?