486 is easily slowed down to 286 levels by turning off the caches.
So, if your only goal is to play games, then no real need for a 286.

Grzyb wrote on 2024-08-12, 23:35:

486 is easily slowed down to 286 levels by turning off the caches.
So, if your only goal is to play games, then no real need for a 286.

Is that something that needs to be done in the bios or is there an easier way to do that?

Tempest wrote on 2024-08-12, 23:42:

Is that something that needs to be done in the bios or is there an easier way to do that?

Internal cache can be disabled using DOS software.
External - probably not, at least I've never seen any appropriate utility.

In my experience there aren't a lot of games that are best on a 286 specifically. The only one that comes to mind is Police Quest 2. Its intro sequence is speed sensitive and runs best on an 8 to 12 MHz 286.

I would agree with Grzyb's suggestion of trying to just throttle the 486 if you really wanted 286 speeds. On my 486 DX-33, I can get to 286 speeds with a combination of the turbo button and disabling internal cache using SETMUL.

I have a bunch of XT motherboards, most NOS, then a massive jump all the way to 486 and beyond. I've never felt a need for 286 or 386 systems. The XT is necessary to play all those earliest 4.77mhz speed sensitive titles, like what was on the apple 2 and other 8 bit computers. I remember playing Wing Commander on my dx2-66 with the Turbo off quite nicely.
My first pc was that 486 so no personal nostalgia for 286 or 386.

I wouldn't say no to an AT. I think it would be kind of fun trying to modernize it while keeping to it's limitations, things like sound, network that were crazy expensive at the time.
But I doubt it would get much use outside tinkering. Most of my games even the really old ones work on a 486.

I don't know if you need a 286, but the AT sure is a looker. One of the best looking PCs of the 80s.

Yeah the AT case is just so cool looking. Actually I wouldn't mind an AT upgraded to a 486 (if such an upgrade exists).

Tempest wrote on 2024-08-13, 01:17:

Yeah the AT case is just so cool looking. Actually I wouldn't mind an AT upgraded to a 486 (if such an upgrade exists).

There are upgrade processors designed to turn a 286 into a 486. However, they tend to be rare and expensive these days.

It's also possible to swap an entire 486 motherboard into an original IBM AT case. However, since unmodified AT system are becoming increasingly uncommon. I would only consider it with an already modified system or a clone.

Putting a 486 board inside an AT case would be a bit silly with only a pair of 5.25" drive bays.

Yes it would silly, but that doesn't mean I haven't seen it done before.

Shponglefan wrote on 2024-08-13, 02:09:

Putting a 486 board inside an AT case would be a bit silly with only a pair of 5.25" drive bays.

Lots of people did it. Why do you need so many bays? You have one for a 5.25" drive, and one for a 3.5" drive on an adapter.
If you absolutely "need" a CD-ROM drive, you just remove a floppy drive or get an external parallel or SCSI box.
There are also three internal 5.25" bays, though given basically nobody uses winchester drives anymore, you don't really need any of them.

Indeed. A common trick BITD was to put a RODYNE or RACORE hardcard in one of the slots, and use the AT case.
Another, was to replace the full-height 5.25" floppies with half-height ones with a little metal bar connecting them, then do the same thing with some winchester drives in the second bay (when using an XT chasis, which has the same board hole-pattern)

The more radical and extreme out there, would have used a SCSI card and an external enclosure.

They made versions that were hella-beefy full-height drives stacked on the controller card. Old AT chasis used to have little plastic support slots in the back of the case to help support these very hefty cards.

Anonymous Coward wrote on 2024-08-13, 09:53:

Lots of people did it. Why do you need so many bays? You have one for a 5.25" drive, and one for a 3.5" drive on an adapter.
If you absolutely "need" a CD-ROM drive, you just remove a floppy drive or get an external parallel or SCSI box.
There are also three internal 5.25" bays, though given basically nobody uses winchester drives anymore, you don't really need any of them.

For clarity, I'm talking about in a modern context. Putting a 486 into an AT case when more flexible desktop (or tower) cases already exist seems a bit silly. Unless one is specifically doing it just for the sake of it.

And for a 486 system, dual floppy drives was standard and a CD-ROM drive was common upgrade of that era. Yes, one could remove a drive or use an external CD-ROM in one had only two bays.

But if one is building one from scratch, a case with more drive bays seems the most obvious solution.

There's always a reason to buy anything not already in your collection. Completionism. OCD. etc

Personally though, I'm slowly selling off most of my collection, due to excessive hoarding (the collection is larger than my bungalow, so no room left to set systems up and test)

debs3759 wrote on 2024-08-13, 12:24:

There's always a reason to buy anything not already in your collection. Completionism. OCD. etc

Personally though, I'm slowly selling off most of my collection, due to excessive hoarding (the collection is larger than my bungalow, so no room left to set systems up and test)

At least with PCs you can use a KVM to consolidate space. I have my 486, Pentium 1, Pentium 4, and PowerPC Mac all hooked up to one monitor which is handy. My 5150 is using a 5151 monitor so that can't be hooked up to a KVM.

Any Reason to Own a IBM AT If I Already Have an XT and a 486?

Do you need one? 😁 The question should be whether you want one or not.
The IBM AT Model 5170 is the mother of the modern PC, it introduced CMOS Setup, Real-Time Clock and the AT keyboard layout.

Compatibility wise, it depends.. It's true that many 486 PCs can be slowed down to 386 and 286 speeds, but speed isn't everything.
There are rare situations in which a typical 486 or 386 system has compatibility issues with 286 era software.

For one, the 386 and up no longer have LOADALL instruction.
There's an 386 counterpart, but it's not same.

On a 386 system, the BIOS must emulate the 286 LOADALL to other software.
Then there are undocumented opcodes not working same on 386 and up.

The same can be said about the original 486, too, by the way.
Some flight sims used undocumented 486 opcodes that broke them if run on a 486DX4 or Pentium-

Ok, that's all pretty academic and not important to playind DOS games.
To people tinkering with Microsoft XENIX or OS/2 1.x, it might be relevant, though.

Other exotic OSes like Wendin DOS or DOS Plus 1.x (just to name something) might be more stable on a true IBM XT or IBM AT hardware, as well.
These OSes pre-date the 90s era hardware and may expect to see true vintage hardware.

In case of OS/2 1.x, this might be a true IBM AT Fixed Disk Adapter rather than a random IDE host adapter on an multi-i/o card.
The difference is big, because the WD1003 command set does not feature many of the IDE specific features yet (no auto-detect feature for example).
It also behaves slightly different in certain cases, which is enough to break something.

Anonymous Coward wrote on 2024-08-13, 01:08:

I don't know if you need a 286, but the AT sure is a looker. One of the best looking PCs of the 80s.

No way! 😁 *Ahem* It's okay looking, but no match to the Schneider Tower AT! 😁
That's one pretty computer, next to the Sharp X68000..

I wouldn't call the AT a 'looker' but it has that boxy IBM style that I love for some reason. All my classic PCs are IBMs except my P4 which is a Dell.

Sounds like between my XT and my 486 I shouldn't have much trouble running most games (at least the ones I care about). I'll have to look into this SETMUL program for disabling the cache, I've never heard of it before.