Never seen a 286 board with a coin cell. Every one I've had has used a 6V lithium on the ext battery header or a barrel battery

Maybe your best chance may be looking for one that already has been modified to fit a 2032 style battery. Or, if you're not afraid of soldering, change the old barrel yourself.

Some have connectors for an external battery so you can just disconnect the barrel and plug in the external one.

Also never seen a 286 board that didn't have the external battery header. Just chop off the barrel battery cancer and plug in a lithium primary. No need to mod anything

lalakobe wrote on 2020-06-21, 15:37:

Hi all! […]
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Hi all!

I want to assemble a 286 machine and I need some advice from you guys.

What 286 motherboards are considered better than others? What models should I look for?
AFAIK there were motherboards with SIMM slots, were they more or less common? Should I try to buy one?
Were there models with CR-2032 CMOS batteries or they all required 4.5v at these times?

Thanks in advance!

I'm not an expert myself on 286 motherboards or which chipsets are considered to be the best.
Some chipsets that come to mind are Headland's HT12 & GC101A-PC chipsets, VLSI's VL82C10x , UMC's UM82C206 & Suntac's ST62c2xx chipsets.

Some of the later motherboards had CPU's from AMD & Harris that went up to 20 MHz (Harris also made a 25 MHz CPU), so you have to decide what CPU speed you're after. The most common ones that I've seen are mostly 12 MHz CPU's.

Yes, there were later 286 motherboards that did have simm sockets (my Suntac J-286P motherboard has simm sockets, in combination with some DRAM sockets). There were slightly older 286 motherboards that used SIPP memory (which are electrically compatible with 30-pin simms), but finding SIPPs these days are almost impossible. You can, however, convert a simm into a SIPP or, just remove the SIPP sockets on the motherboard and solder on 30-pin simm sockets (from a donor motherboard).

I would simply just connect an external battery pack to the motherboard (almost all the motherboards from that era had external battery headers). Just remember that a CR-2032 is not supposed to be charged, but you can place a diode in between if the circuit is trying to charge the battery. However, older motherboards (like your 286 & 386 motherboards) normally required at least 4.5V when connecting an external battery pack (due to the diode that reduces the voltage output). You will most likely find that a 3V CR-2032 will not provide sufficient voltage to keep all the settings in the BIOS . You can safely even connect a 6V external battery pack to the motherboard (some 286 manuals even specifically mention this).

I would try to find a 286 board that has a 12Mhz or 16Mhz cpu and SIMMS slots. The Headland HT12 is a good chipset as mentioned above. Back then most used barrel Varta but most good boards for sale it is already removed, just use a 3 AA battery pack with Alkaline batteries and connect to the 4 pin header as mentioned already (though I disagree that it should be 6v, 4.5v is usually more than enough and you will know if it does not keep CMOS settings, all of my 286 and 386 work fine off 3 x AA though there are a few rare boards that do require 6V external. One actually has no onboard battery but has a three AA batt pack mounted to case. Always better to be on safe side and use less unless you know for sure !).
edit: shit meant 286 and 386, been working on XT parts all day... my bad

maxtherabbit wrote on 2020-06-21, 15:43:

Never seen a 286 board with a coin cell. Every one I've had has used a 6V lithium on the ext battery header or a barrel battery

Ex-Kwik Trip Harris 25mhz white box low profile units had an ISA RISER, decent modern bios, good vga onboard and a coin cell, some of these units took 72pin Simms which was interesting. They were used as POS management units with a proprietary software environment.

Despite being very late they still had even at the time ancient 40mb or 80mb IDE drives, some had ram soldered onboard others did not but all seemed to have 4mb fitted regardless.

Wish I would have kept one, at the time it quit working and I re-used everything I could in a different 16mhz 386DX machine, don’t remember the brand but I think these 286’s were circa 1992!

The DX I replaced the 286 with was a pile, had the 32bit bug making it so I had to hack just to get into Windows standard mode, everything seemed half as fast

rmay635703 wrote on 2020-06-22, 02:58:

Ex-Kwik Trip Harris 25mhz white box low profile units had an ISA RISER, decent modern bios, good vga onboard and a coin cell, some of these units took 72pin Simms which was interesting.
Despite being very late they still had even at the time ancient 40mb or 80mb IDE drives, some had ram soldered onboard others did not.

Wish I would have kept one, at the time it quit working and I re-used everything I could in a different 386sx machine, don’t remember the brand but I think these were circa 1992!

My friends mom bought a Laser/Leading Tech 286 back about 93 and it had a ISA riser and Simm slots and a 40MB IDE (not eide), not sure about the coin battery because it was when I in my early 20's. I believe you and wish I could find that same old machine, iirc it was an AT5500 or 5500AT model but that could be wrong, my memory is not that great lately...

Some chipsets that come to mind are Headland's HT12 & GC101A-PC chipsets, VLSI's VL82C10x , UMC's UM82C206 & Suntac's ST62c2xx chipsets.

What about G2 (or later Headland) GC102 chipsets? Are those normal?