Site icon xiphod

Project Xiphod 386: About this 386

Advertisements

BACK to main Project Xiphod 386 Summary

TABLE OF CONTENTS

Overview of the mainboard

I came across this particular 386 at a local area Retro Computing get-together. The drives were loose, the original 3.5″ drive didn’t work. The power button was missing (though the interior switch still works). It was in overall clean condition and the front panel switches were all still hooked up to where they needed to be on the motherboard. But it is what we could call a “no-name brand” system (“POSITIVE” for the case and “MOTHERBOARD FACTORY” for the mainboard; the board is marked 1990, while the BIOS has 1989).

NOTE: “Turbo” buttons were in fashion for 286, 386, and 486 era. This was a stepping stone towards the industry understanding how to run CPUs more dynamically in speed, which (ideally) could save a bit of power. The turbo button on this 386 allows reducing down to a “bare-minimum” 386-16MHz.

From a prior article, I determined the mainboard in this system is identical to a Northgate Slimeline 320.

The “tree” expansion offers room for 3x 16-bit ISA and 2x 8-bit ISA. The reason this motherboard has so many chips is because it has VGA, serial/parallel IO, and RTC all built right onto the board.

Expansion Card Selection

No expansion cards were originally included, since with so many features built in it didn’t really need any expansion cards to boot and become a useful system. As was expected, the CMOS battery needed to be replaced. I kept looking for a typical CR2032 disc battery, until remembering that in some builds the battery was hidden inside a large IC – which this one was like that.

The 16-bit cards I did end up adding are:

After testing a variety of cards (across ATI, Orchard), I’ve recommend an STB (STB SYstems) card or Diamond 16-bit ISA VGA card, which were very popular starting around 1991 to 1994.

Replacing the I/O Card

(replacement #1)

A note about the parallel port: While swapping the SDLPT when the system was powered, I heard an electrical pop and knew that wasn’t good. The onboard parallel port stopped being responsive. Everything else in the system still seemed fine, so luckily that was the only damage. Fortunately it was easy to disable the onboard parallel port, and there was one expansion slot available to add in a replacement IO card. “IO cards” are available in all variations of having serial ports, game ports, parallel ports, and many often include their own RTC (real time clock) replacement. Here is an example of one such “all in one” I/O expansion card (using a 16450 UART):

For this situation, I sought out a simple card that just had a single parallel port (then tape over the onboard DB25 port to reminder everyone it doesn’t work anymore). Sacrificing an entire slot to this is my punishment for having damaged the onboard one (but also quant to have an original IBM part put back into operation).

(replacement #2!)

Later on, while testing conex 7.5 (terminal program like QModem) and LapLink and FileMaven (which can do both serial null modem and cross-parallel cable data exchange), I found that it appears the onboard serial ports were also damaged. I set the jumpers to disable them and sought out a more advanced I/O card (that is, one that includes more than just parallel port).

I settled on the DIO-200X Multi IO card, which has Game Port, Serial, Parallel, option for 1 extended serial, and RTC. The card is from about 1988. The manual has been digitally archived and is available here: Diamond Flower DIO-200X Users Manual.pdf

I made a video about upgrading this card (adding a 16550 UART as the 2nd COM port), which is located here: Upgrading an 8250 to 16550 UART in 2025? Who does that!? I can explain!
( https://www.youtube.com/watch?v=qJTZv9sEYMk )

Selecting an Operating System

The included 3.5″ disk drive didn’t work. Luckily, I had previously gotten re-conditioned and tested 3.5″ disk drives earlier at VCF SoCal. I didn’t need them at the time, but I had a feeling someday I would (and I appreciated talking with the old gentleman who had refurbished them). And so, this was the system to benefit from that. Then fortunately, aside from not being bolted down securely, the 5.25″ disk drive has so far worked flawlessly. A friend imaged a 320KB (yes, 320) MS-DOS 2.11 for me (FAT12), which it was able to boot that – although it was one intended for a SHARP computer, it did still boot ok. That commitment to backwards compatibility is admirable.

FreeDOS also works on this system (which lets you use large capacity drives that are over 2GB). But I decided on keeping this system closer to the 1992-era, which meant using MS-DOS 5.0 (which was released in June 1991 while the famous MS-DOS 6.22 was released later in 1994). It was fun finding an original MS-DOS 5.0 set of 3.5 disk (3x of them) and installing the OS from that original media.

The manual for MS-DOS 5.0 is still very extensive, in covering each command and included program. But MS-DOS 5.0 was a very “weird” time for Microsoft – they were “secretly” building up Windows as their mainline product (in competition to OS/2), and desperately trying to cross the threshold of being a “GUI app on top of DOS” versus a ground up “first class operating system” (with a GUI). Linux still wasn’t really on anyone’s radar by 1992, it was still more of an academic curiosity at that stage.

The main issue about MS-DOS 5.0 was that the 386 memory manager it included wasn’t very good. Or more specifically, Quarterdeck was a third party software vendor that provided a still superior memory manager (in terms of just easier to use). So I do still use the period-correct versions of DESQView and Quarterdeck Memory Manager (QEMM386) on this system.

About the Sound Card and Network Card

Upgrading past the original Sound Blaster that I used in my IBM PC 5150 system, I chose the period correct Sound Blaster Pro. Wing Commander 1, the “SimCity Classic” update run excellent on this system. There were no particular issues installing this sound card. However, I noticed the SB gamepad stopped responding after I installed the serial card that also had a gamepad port (even though I wasn’t using it).

Basically I was forced to set the jumper to disable the SB gamepad port, and use the one off the serial I/O card. I came across a few MS-DOS joystick test programs that verified this.

I used the same network card as in my IBM PC 5150, those notes are available here. The same mTCP tools work here, and I can FTP files across the system.

Using an ISA-USB adapter

“ISA” is the standard IBM PC bus available in the original IBM PC in 1981. The “expansion bus” concept can be found in earlier PDP-8 models and later S-100 based systems (Sol-20, Poly-88, Altair, etc.). I came across an expansion PCB device that claims to allow supporting data exchange with a USB thumb drive. Being a “tree” style system, this Slimline 320 system was out of expansion slots.

So I’ve put together a friend for this 386, a slightly faster 386DX-33, and explored using this ISA-USB expansion card on that system. Details about that card are here.

Closing thoughts on this 386

This a nice addition to the collection – desktops take a lot of space, so I’m a bit selective on which ones I collect. The IBM 5150 is great for exploring the “origins of the PC industry” and going all the way back to a 16K boot-to-BASIC configuration, with CGA. But late 1980s software does start to struggle on that original system (things like SimCity, Flight Simulator, AutoCAD).

Another thing this build highlights is the “open standard” nature of the PC hardware industry – of being able to buy parts and assemble your own working PC. IBM had paved the way (in the 1981 PC launch) and in 1987 began their newer PS/2-series (which appealed to schools, government, hospitals, businesses who felt compelled to stick with the reliable IBM brand). But for home consumers, PC-clones were abundant: DELL, Compaq, Packard-Bell, Gateway, Tandy and countless others.

But one point of contention was the IBM PS/2 MicroChannel bus, which apparently IBM did try to license that – and the PC industry just steered around it, evolving onward to AGP and PCI bus. This approach ended up biting IBM again later, when they tried to license the PowerPC CPU.

By early 1990 home computing, it wasn’t unusual to say that IBM was out of the picture as a household name. IBM still focused mainly on business-needs, and did well on “POS” (point of sale) systems (you’d often see IBM-based cash registers in stores). Also in my experience, many universities and businesses did continue to have confidence and used IBM PS/2 systems (but they weren’t commonly used in homes). IBM did have massive success with their ThinkPad line throughout the mid-1990s. But as far as desktop home computer, smaller shops had verified-compatible pre-packaged models. Custom building your own was also not unusual (as an increasing number of local shops were available with parts to assemble a full PC). The “PC industry” had asserted itself by 1993, and many competitors (Tandy, Commodore/Amiga folded around this time; even Apple nearly folded at this time, but managed to pull through after the release of the iMac). Things got even easier in home assembly of a PC when the ATX mainboard configuration and power supply connector was introduced in 1995.

“SW3” (switch block jumpers group 3) at the top in the diagram below is where to enable/disable onboard serial and parallel ports.

References to this Northgate Slimline 320 (same board as this):

Exit mobile version