You're not limited to DOS, Windows 3.1 will work (but very slow), OS/2 1.x also, there are also UNIX clones for the 286 (Coherent, XENIX) and there's NetWare.
You might encounter issues, if the manufacturer of the hardware you want to use expects a 386 - some provided only drivers which required a 386.

just get a board that has 16bit slots and use vga/ide/i-o cards, it works fine

The 286 system was the first AT class system.. So everthing that works on a 386 would work on a 286.

About the slots.. First you need to know which cards you want to install.. I prefer to occupy 8 bit cards mostly to put in 8 bit slots as much as possible.. So you have more 16-bit slots left for your 16-bits cards that take the benefit of it.. I know that some people put just 8-bit cards in 16-bit slots.. But i think its just a waste of bandwith.
An 286 system is much easier to build then building a XT system.. With a XT system you have more limitations..

- XT needs an XT keyboard (AT doesnt work, or it may need a switch on the button the switch to XT mode)
- An XT needs more expension cards.
- Cant install to big harddisks, or the disk calculation would be terrible slow
- Only 8 bit slots.
- Runs better / faster on CGA / EGA graphics
- Standard floppy controller can only handle 720KB ones, or you need a special card to handle 1.44MB but does are not easy to get by now.
- System can only cope with conventional memory and / or EMS only.
- Standard no CMOS program
- Standard no RTC.

The benifits of an 286

- Mostly that are faster.
- 16-bit slots is a main advantage! easier floppy controllers to obtain.
- Can handle bigger harddisk (processor is no limit here on 12mhz)
- Have CMOS program (maybe not the best you ever have seen, but better anything then nothing.
- Have RTC standard.
- Can cope with all of the AT class keyboards.
- Can work with lesser expension cards.
- Does have extended memory.

Only the downside, some programs are more written for the 386, because the 286 had a realmode to protected mode bug in the system / processor.. That was solved later on the 386.

You can just install MS-DOS 6.22 if you want.. But for myself i prefer (more time wise) to go for the MS-Dos 5.00.
If you want windows to.. Windows 3.0 would do the trick, but i prefer to use windows 3.1 instead.

You can use any DOS version and Windows up to 3.11. I recently gave up a 286-12MHz, 4MB ram and 40MB hdd... it ran Win 3.1 quite well. Main thing is to have at least 4MB ram for Windows.

Usually there is no issues with ISA cards (PnP ones can have a driver problems - req.386).

4MB on a 286 is useless.. 2MB is already more then enough.. I should invest in a bigger harddisk. 40MB would be normal. But will be full in no time, if you want to install a bunch of games on it..

How i do it?

XT = 66MB /80 MB drive
286 (i prefer go for the biggest FAT16 drive supported by bios) 500MB (or from 200MB - 500MB will do)
386DX40 (i prefer go for an 1.3 GB)
486 i prefer about 4GB
Pentium 1 i prefer 20 - 40 GB
Pentium II i prefer 60- 80GB
Athlon XP, AMD Athlon 64 / Pentium 4 i prefer 200 - 500 GB.

Then you dont have to worry about disk space..

Even 1MB is enough if you don't plan on using Windows and other "more" damanding games/apps. But for Windows 4MB is great for "smooth" operation. Usually 1MB SIMMs are so cheap that it would be a shame not to fully populate ram slots (that is if the motherboard has SIMMs).

What I personally look for in a 286 board is that it have SIMM slots and a PLCC socket so it can at least mount the fastest speed grades of 286 even if a clock crystal upgrade is required to change the speed and all the ISA slots should be 16-bit, no 8-bit slots. And no proprietary OEM boards. Chipset should be Headland or C&T, as they have the most success running the fastest speeds. To me, if you're going to build a 286, then it should be a later, high end 286 instead of one of the older, slower models.

sliderider wrote:

What I personally look for in a 286 board is that it have SIMM slots and a PLCC socket so it can at least mount the fastest speed grades of 286 even if a clock crystal upgrade is required to change the speed and all the ISA slots should be 16-bit, no 8-bit slots. And no proprietary OEM boards. Chipset should be Headland or C&T, as they have the most success running the fastest speeds. To me, if you're going to build a 286, then it should be a later, high end 286 instead of one of the older, slower models.

Then you can look for a long time.. 286s boards with Simm slots are very rare, mostly they are just dips only.. Or sometimes they are a combination of dips and Sipps,
Best is to find a Sipp motherboard and then customize it with Simm slots.

And PLCC is indeed better, it doesnt require the cooling plate.. because those cpu cooling plates are hard to get.
For the best bet, 12Mhz is just the best scalable platform.