Being a retro PC enthusiast, my eyes are always open for deals on old hardware. A couple of weeks ago I came across an eBay listing for an as-is “Motherboard with ISA slots”. Looking closely at the posted images, I could see that the board was late-80s to early-90s vintage with sockets for individual memory ICs rather than the usual 30-pin SIMMs. Straining my eyes, I could faintly make out the markings on a Siemens brand 12MHz 286 processor. Having never owned a 286, I thought this may make a fun new project.
It was listed as-is because the seller didn’t have the hardware to test it. This is always a risky proposition, but when dealing with AT based systems, chances are that most people genuinely won’t have what’s needed. This is especially true if the seller doesn’t specialize in vintage hardware – which seemed to be the case here.
After scouring the web to determine what I had just bought, I was able to confirm it was the Biostar MB-1212V. A VLSI chipset based 12MHz 286 system. Although the 286 CPU was made in Austria by Siemens, this is actually Intel’s design. Intel authorized several manufacturers to make their 286 processors for them. You can find 286 processors from Intel, AMD, Harris, Siemens IBM and others. Some interesting history can be found on the 286 Wikipedia page.
I had most of what I needed to test out the system when it arrived, including an ISA VGA card, AT PSU, and 5-pin DIN compatible keyboard. The only part I was missing was an ISA multi-I/O card. Rather than rushing to buy one, I would first ensure the system posted and that I could get into the BIOS. What I had should be enough to determine if it’s worth proceeding.
The VGA card is an ATI Mach 32 dated 1993, which I recently picked this up from the great folks in the computer recycling department of The Working Center in Kitchener. It was sitting in a box full of old PCI graphics cards destined for e-waste. It’s always awesome to keep classic parts out of the landfill and support a great cause at the same time.
Booting it Up
To my delight, the system posted without issue.
It was an AMI based system with a ROM dated 1990. At 28 years old, this is the oldest piece of AT-based hardware I have in my collection. I didn’t know how much RAM was in the system when I bought it, but with two banks of 16 ICs, I had assumed it was 4MB. This was confirmed once the POST process completed.
As expected, the CMOS battery doesn’t keep its charge very long. I was surprised that after charging for several hours it still manages to maintain a little under 2V. The time is not being kept, but the BIOS settings are retained. Given the age of this system, I can only assume that the battery was already swapped out at some point in the past. I’m just happy it didn’t leak and corrode the surrounding traces and components. The board does have an external battery header just like my 486 system so I’ll look into constructing a similar external battery pack for this system and remove the barrel battery.
Once I was satisfied that the system was more or less functional, I bought a 16-bit ISA I/O card. This model is dated 1992 and based on the popular Acer M5105 chipset. It is a typical I/O card with a single IDE channel, a floppy controller, two serial ports, a parallel port and a game port.
The exact model of the card is the UN-1051 by ‘Micro Equipment Corporation’. A full list of jumper settings is also available at the very useful PC info section of statson.org.
For an IDE hard drive, I used the handy Sintechi SD to IDE adapter and a small 512MB SD card. Because this system is 510MB limited, it’s the perfect size. The card is very old – from one of my first digital cameras – but the system is so CPU bottlenecked that it should be quick enough. You can find more information on this and other storage solutions for retro rigs in my previous post here.
A 16-Bit World
After configuring my floppy and IDE settings in the BIOS, I was able to boot without issue. I booted DOS 6.22 initially but decided to install 3.3 once I finished some basic testing.
MS-DOS 3.31 and Windows 2.1 seemed like a good late-eighties combo. It’s pretty eye opening just how bare-bones DOS 3.3 is compared to 5.0 and 6.x. Reminding myself of how to use edlin instead of the MS-DOS Editor was not fun.
DOS 3.x doesn’t include an XMS driver like that in newer versions of DOS. The 1988 version of HIMEM depicted above was actually provided by Windows 2.1. Although I was able to take advantage of XMS memory, 286 systems are not able to use EMM386 for EMS emulation.
This 12MHz 286 system has only about 1/4 the raw processing ability of a 33MHz 386 system. The turbo button header on the board is also functional, but the resultant 8MHz clock is only a one third reduction. I can barely notice a speed difference with it in this mode.
One of the unfortunate things about being limited to 16-bit code is that many DOS tools, games and utilities were optimized for 386 CPUs over the years. The popular chkcpu tool is one requiring a 386:
There are many other examples, but Speedsys wouldn’t run, nor would ‘Windows 3.11 for Workgroups’ due to the 32-bit optimized network stack it includes.
A good number of classic games will run just fine. I had no problem running any of the Commander Keen titles as well as one of my favorite side-scrolling games – Hocus Pocus.
One thing I noticed was that the usual jerky motion problem that Commander Keen exhibits with ATI cards was nowhere to be found on this 286. Processor speed must be playing a role with that problem, as the same Mach32 card makes Commander Keen unplayable on my 486.
I was also able to play Wolfenstein 3D, Ultima 4, Alien Carnage and Duke Nukem 2. Wolfenstein 3D was choppy, unfortunately, but shrinking the view area made it very playable.
The key thing to remember is that this is a CPU architecture designed in 1982 – you’ve got to use software from the correct era.
Anyhow, it was a fun project. I don’t think I will be building a permanent system out of this, as I still can’t find a suitable AT case for my 486 restoration. If anyone knows of a good place to find AT cases, please let me know!