My First 486 Build

I’ve always had a soft spot for the 486 since this was the generation of the first PC I ever owned. Getting a 486 has been on the short list of computers I’ve been wanting for quite some time, but I've been holding off because of the price.  I'd love to buy my original 486, a slimline Gateway product from 1993/94, but they have become both rare and expensive.  The next best thing would be to do a build from the era which would be a great learning experience since I wasn't doing builds at the time.  Frankly, at the time, I didn’t know enough about computers to do a build, but thanks to the Internet and the willingness of the Vintage and Retro Computing community share their knowledge, this is no longer the barrier than it once was.

One of my retro computing friends had a board from an old build that he wasn't using, and he sold it too me at a good price, along with a Cyrix 486DX2-66 Processor and some RAM.  This is a 386/486 board with VLB.  It was an offer I couldn't refuse, even though I didn’t know where I’d find a case.  Within a few days a case popped up on Craigslist from a trusted seller, so at that point I knew I had to start the project.

I was able to gather the parts and start into the build.  The case was a donor from a PC with an older 386 Motherboard that had an exploded battery.  It had been cleaned up some years back, but the board has an A20 Gate Error on boot.  I did some preliminary troubleshooting on this, but as the seller had already warned me, there was nothing obviously wrong with the board.  I may come back and make another attempt at repair later but I set the older 386 board aside for now and turned to cleaning the case.  This was a system from 1990.  It was dirty and the plastics had yellowed, as you can see here...

I took the case apart, and took the LEDs and switches out, just as you will see many of the smaller YouTube channels doing like Necroware and RetroSpector78.  I really enjoy the process of cleaning this old gear up and getting it looking better again.  Sometimes it's not possible for me to get it back to complete like new appearance, but I know I got the case front looking significantly better...

The plastic front still doesn't quite match the painted metal, but I don't have a very powerful UV light on my retrobright tank, so it took a couple of days to get too this point.  I may need to think about an upgrade at some point on the UV LEDs in the tank.

Once the case was cleaned up it was time to start the build.  The 486 motherboard I already mentioned has a BIOS on it from 1994, so I decided that the timeframe for the build was going to be a system  thats started out in 1990 (with the case) and had gotten upgraded over the years up until the mid 90s, I didn't want to use any gear in the build later than that.  Also, I didn't want to spend an arm and a leg, so that meant (mostly) making do with parts I had on hand.

One of the first things I needed to deal with was cooling of the 486DX2/66.  I had a heatsink from a Dell machine, but the heatsink alone wasn't enough.  Since there isn't much airflow in this case, I added a fan inside to blow air directly over the top of the processor while the machine is on.  This keeps the CPU cool to the touch even after hours long periods of use.

The specs of the build at the start were:

486DX2/66

5MB RAM

Cirrus Logic ISA VGA Video Card w/ 512 KB RAM

16 Bit ISA Disk Controller Card w/ IDE2SD Adapter, and 1X Sony IDE CD ROM

Super IO Card for Serial / Parallel ports

Opti 82C929A Sound Blaster Compatible

Being the first project of this kind that I've tackled, there was quite a learning curve.  The early PC stuff that I've worked on really doesn't have that many options and frankly you just can't get that much performance out of them,  This 486 system is pretty different.  I was easily able to get the system up and running, but the performance was horrible when I ran the tools in Phil's DOS Benchmark Pack.  (3 fps in SuperScape) And probably more important, it didn't perform anywhere near what I remembered from my 486 in games like Star Wars X-Wing, Wolfenstein 3D, Doom, etc.  I got discouraged and put the build on hold for a couple of weeks because of this.

I tried quite a few things to remedy this situation.  First, I did a RAM upgrade, bringing this machine up to 20 MB RAM, which would have been a shocking amount of RAM back in the day.  My PC had either 4 or 8MB at that time.  Sadly, increasing the RAM did not help.

I also asked for advice from a friend at Free Geek Twin Cities about doing a VLB upgrade of the Graphics card and Disk Controller, but that was going to end up costing almost as much as the rest of the build just for those two cards so I abandoned that idea.

I ended up going through the AMI BIOS settings one at a time, googling those settings that I wasn't familiar with, and trying to understand how those affected machine performance.   What I ended up landing on was this article on the Vintage Computer Forums.  The key to unlocking the performance on this machine was the AMI Bios setting:
Advanced Chipset Setup / AT BUS Clock
The default value was CLK1/6
I changed this to CLK1/4 saved and rebooted.

The machine performance was vastly improved (27 fps in SuperScape), and more important, X-Wing runs like it should.

There were various other minor things that came up along the way during the build but after the bus speed was set correctly the machine has been running really well.  I’ve been getting a lot of enjoyment out of it.