486 Build Part 1: Hardware

By: Nicolas Foster

This guide is intended mainly for retro hardware and software enthusiasts, but it can potentially help those who manage legacy systems within professional environments. The 486-computer documented within this guide is from the early to mid 90s. This guide is not a purist guide as I use many modern components in this build. The new components are crucial to relieving bottlenecks, anachronism, and obsolescence of aging hardware.

This guide helps in preserving some of the past by utilizing current technologies. I will demonstrate how to move past the floppy drive by using a hardware emulator and leave mechanical drives behind by embracing flash memory. Such an agenda is born out of my own learning within the hobby and my desire to make retro-computing sustainable and cheaper for myself. The actual augmentation of retro computers doesn't have to stop at drives. AT PCs motherboard actually fit into modern ATX cases. Power adapters can be purchased to allow a retro computer to use a modern power supply. Since the PC open standard hasn't changed that much over the years, retro PCs are by far the easiest to build and maintain. Also due to the popularity of IBM PCs and clones, the actual standard transcends the PC itself. For example the floppy drive emulator used in this guide is also widely used for retro musical keyboards. In fact that is likely the most dominant use case for a floppy drive emulator but retro hobbyist can capitalize off of it because of the popularity of such a standard in the late 80s and early 90s.

A warning to anyone entering the hobby! This hobby is expensive at best and very expensive at worst. Be prepared to fight the urge to collect many pieces of retro-computing. Try to find a niche within with the retro-computing hobby and fully embrace it. This not only helps with cost but it also helps build a compounding knowledge pool. I have personally chosen to focus on the early and mid 90s PCs but there are many different systems retro-computing hobbyist can embrace. Old Macs, Amigas, IBM PS/2s, Commodores, and even consoles can be embraced and worked on!

List of hardware being used:

Motherboard (Mainboard) with a AMD486-40 CPU:

RAM includes 4 x 30pin 4MBs Micron SIMMs, and a 72-pin 4MBs Kingston SIMM for a total of 8MBs:

WDC (Western Digital) ISA Video Card:

Sound Blaster 16 ISA Sound Card:

IDE Controller ISA Card (used to connect Hard Disk and Floppy Drive):

The Hark Disk is an emulator. This device will enable much greater flexibility than a traditional mechanical disk as I will demonstrate later in this guide.

Please note that I modified this device with a metal bracket. The metal bracket is from a random device I had. I needed to use epoxy because the holes didn’t line up. I could have easily expanded the holes on the pcb with a knife to make this bracket fit but I just used clear wield epoxy. Putting a bracket on this device allows me to mount it differently. This device could be mounted in the same place as a traditional drive though:

The back of device shows modification:

The floppy drive is an emulator. This device uses USB drive which is partitioned 100 times into little 1.44MB partitions. These partitions act as a floppy disk. Buttons on the front of the emulator are used select the specific floppy:

Old AT power supplies are very old and they can have bad caps, so they have tendency to break during use. This can cause damage to the mainboard and components. If you intend to use a old AT PSU then do a recap of capacitors so that the PSU wont damage the system. An AT to ATX power supply adapter is used in this build so that a modern ATX power supply can be used.

This build also uses an AT DIN to PS2 keyboard adapter (Bottom) so that using expensive and old AT keyboard can be avoided:

A hacked together AA battery will help power our CMOS settings which the BIOS uses so that settings don’t disappear when the machine is powered off. Even if a battery is not used, the computer could still be operated, but it would lose its BIOS settings every time its either powered down or powered down for a specific and undefined amount of time. The BIOS would then require setting input every time the computer is powered on. That would get old quickly.

I find this hack works well. I ordered a retro motherboard on eBay and it came with this battery. It looks like someone just cut the wires off an old speaker. The three holed plug looks compatible with both speaker and battery jumpers. Red wire is positive and black wire is negative.

Just note that this is not the best way to power the CMOS chip. Soldering a CR2032 battery holder where the Ni-Cd barrel battery would go is a better example of how to power the CMOS chip:

Right next to the battery jumper is where the Nickal Cadmium (Ni-Cd) barrel battery would go. Such batteries have destroyed many retro computers. Over time they leak and corrode the main board by eating into the copper traces and other components on the mainboard leaving a teal copper patina.

Here is an example I have encountered and documented. I removed the barrel battery:

Another critical part of this build is a serial mouse. Unlike the PS2 keyboard, serial mice were the most popular mouse connector. I haven't found a VLB or ISA that has a PS2 port. This serial mouse will connect to the serial port on the HD controller card:

Some additional things include VGA cables, VGA monitor, PS2 keyboard, and a C13 power connector:

This build uses an SD card as the hard drive and another computer to back up the SD. An adapter should be used if there are no SD ports available:

Another important tool for this build is the manual for the motherboard. Retro computers use jumpers to configure and define hardware. The motherboards manual is used to see all specific jumper settings.

Head over to https://theretroweb.com/ to find almost any retro PC manual. When on The Retro Web main page click Motherboards and a search page will load. Enter motherboard information:

Do a search with the entered information:

Find the specific board:

Click on downloads where you will find the manual and sometimes some extra stuff like a BIOS image. The BIOS is stored on an EPROM chip located on the motherboard. These EPROM chips can be removed and imaged so that if they become corrupted, they can be reimaged:

Download and open the manual:

Now that we have the manual, we can find important information which for example could help us upgrade the CPU:

Identifying the jumpers:

Upgrade and remember to try to always use a fan. The Am486 DX-40 doesn’t need a fan, but the DX2-66 should have a fan even if it’s not required :

After all the resources have been gather its time to build the computer:

Install the power adapter:

Install the ATX power supply:

Install the motherboard standoffs:

Place the motherboard on the standoffs:

Screw the motherboard in:

Now route the power cords and plug in the power connectors to the proper places:

Connect the battery. When it comes to the AT power connectors the rule is black wire touches black wire. DO NOT plug these connectors in the wrong way as it will cause damage to the motherboard. I learned that the hard way:

Now start inserting expansion cards:

Insert the hard drive emulator:

Insert the Sound Blaster 16 sound card:

Insert the Western Digital video card:

Insert the IDE controller:

Connect the ribbon cables. The key to direction of ribbon cables is the red line on one side of the ribbon cable which defined which side connects to pin 1 on the connector. PIN 1 is highlighted on all the PCBs.

40-pin IDE ribbon:

34-pin floppy ribbon cable:

Boot the system to see if it works:

The best-case scenario is when the decades old computer works for the first time. Many times, things don’t work the first time. Luckily, if you enjoy the hobby then this is fun part begins. You get to troubleshoot! Start removing components to isolate the problem. Most 486 computer of this era generally need only a video card to boot. If you find yourself not booting with a video card and motherboard only then the problem is either something with the motherboard or the video card. The problem doesn't have to be complex either. It could be a simple fix like the expansion card wasn't making good connection. Start working down by removing ram, swap out the video card, and check the power connectors. Eventually you'll find out if you have bad hardware or if its just the personality of the chosen hardware. Sometimes hardware doesn't work for a while but then will eventually work again.

After successful bootup, the HD emulator, SD card, and ribbon cable must be tested. Boot into the BIOS by hitting the DEL key on startup. The example below has a CMOS checksum error and has BIOS loaded defaults. This occurs when the computer doesn't have a BIOS battery and has been powered down for a while:

Press DEL to enter SETUP (BIOS):

Once in the BIOS go into IDE HDD AUTO DETECTION:

The autodetection begins and if a drive is detected then it is confirmed everything is set up properly. We know the IDE card, cable, and HDD emulator works because of the auto-detect hard drive readout. If one component wasn't working then this screen would be blank. Don’t select anything in this menu right now:

At this point we know the power supply, motherboard, CPU, RAM, video card, controller card, and IDE emulator work.

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