Microelectronics | System Design Assembled Machines


I assembled two machines from hardware components that I designed over time.

I wanted two systems because I had a couple of PCBs left from each project. And second to that, I wanted to cover the entire '90s decade in terms of computing performance.

Disclaimer: I reserve the right to change these designs or implementations without further notice. These are entirely hobby do-it-yourself projects and I am not responsible for any damage made by any possible mistake in any version or revision of the schematics or PCB layouts of the computer cards involved in these projects.

This page is work in progress.
I am still adding text and images, time permits.

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Laudatur ab his, culpatur ab illis. This project consists of multiple individual sub-projects, all of them provided as-is and not for commercial purposes. It reflects my experimental work in microcomputer system design and should be treated as such. I release the schematic diagrams and circuit board layouts to the public for educational purposes. I did all this at my own expense and in my free time. If you like my work, please consider making a donation. It helps me continue these kind of projects.

Machine #01: 80386DX / 33 MHz or TX486DLC / 40 MHz

This was the dream that started it all. This is what I had in mind when I started working on all these individual x86 System Design projects.


This machine is made with the following components.

Known Issues

Unfortunately, there are some issues that I haven't had time to address yet.

  • Floppy disk drives do not work -- suspecting DMA problems some controllers don't work while some others do
  • Digitized sound effects do not work -- suspecting DMA problems

In the meantime, I tested multiple ISA floppy controller cards based on the Intel 82077AA or National Semiconductor PC8477BV integrated circuits. None work with this computer. The floppies will seek but will not read or write data. Every floppy access is terminated by a Drive Not Ready error. I even tried an Adaptec AHA-1542CF SCSI adapter that also implements a floppy disk drive controller. That doesn't work either. However, other generic ISA floppy disk drive controller cards work for some reason. I will have to investigate this issue.

Assembly and Pictures

I chose an unbranded AT tower case from the mid-90s decade. It was very dirty, and the plastic acquired a yellowish tint. I might try to retrobright it at some point in time. I quickly converted the case to accept an ATX power supply. In fact, the conversion had nothing to do with the case itself. I have just removed a small retainer metal C-clip from the power button internals. So the button acts like a momentary action switch, and now it is able to pulse the ATX power-on circuit on the system backplane.

These are the two floppy disk drives that I am using with this computer. The front faces are a bit on the gray side. They don't fit the color of the case. But I don't really care about that, given how scarce these floppy disk drives are. Both units are part of the real floppy disk drive series, with a decent build quality and high reliability.

The 1.44 Mb 3½" floppy disk drive is model MP-F17W-02 SMM, made by Sony in 1993. This is the underside. I particularly like the disk motor construction and the heavy duty magnetic shield on top of the motor coils. This unit has an amber front LED.

The 2.88 Mb 3½" floppy disk drive is model MP-F40W-15 SMM, made by Sony in 1993. Again, same construction style on the underside. This unit has a green front LED.

Two CF cards are installed in a dual CF to IDE adapter in a master-slave configuration. This adapter is available in 2½" form factor. I am using a 2½" to 3½" metal adapter that is further installed in a 5¼" adapter.

Here are the two 40 Mb IDE storage devices. These are Seagate ST-351A/X stepper motor hard disk drives. These hard disk drives are not connected to the machine on a daily basis. I am using them only for nostalgia purposes and experimental software that needs to access magnetic drives only. I would've liked the front covers to be computer-grade beige. But they do look retro nonetheless.

This is how the computer looks like.

Although a 7-segment speed display is present, unfortunately, this case does not have a turbo button. It would've been pretty useful for older MS-DOS games that require slower CPU speeds. In addition, the speed display would've switched numbers on the fly. I am thinking about adding a turbo button on the back of the case. It doesn't matter that it is going to be a bit difficult to toggle it as I won't be using this function on a daily basis anyway.

The discolored beige case contrasts well with the black front covers of the storage devices, creating an industrial-looking PC. Initially I wanted to search for a floppy disk drive that matched the color of the case. But I gave up quickly since it's hard to find new-old-stock MP-F17W-02 (or related) drives in beige color. However, I might investigate at some point whether a beige front face from a newer MPF 920 drive will fit the old ones.

In the end, I configured the jumpers on the speed indicator to show 40 MHz.

This gray tone on the floppy disk drives reminds me of early Hewlett-Packard Vectra desktop PCs.

And before you ask, no, I don't actually use the EIZO screen. It is pending complete restoration, and now it just sits and waits for its turn.

Machine #02: Pentium MMX / 233 MHz

Playing DOOM, Quake, Duke Nukem 3D, Terminal Velocity, and the like, require a faster CPU. In addition, I wanted to remember the Windows 98 experience. And since an 80386 CPU is out of discussion and the effort of building a 486 CPU-based SBMC is not worth it for my purposes, I went for an industrial Pentium SBC on a 16-bit ISA card.


This machine is made with the following components.

Known Issues

This machine also has some issues that I haven't found a resolution for.

  • Floppy disk drives do not work -- no idea what is causing this behavior

Assembly and Pictures

The case is an InWin IW-Q500 full tower case that I found dirt cheap at the local flea market. Of course, I had to clean it thoroughly, an operation which took quite some time. But then this case is spacious enough for an experimental DIY computer that will have multiple storage devices and a lot of individual ISA cards.

The 1.44 Mb 3½" floppy disk drive is model MP-F17W-02, made by Sony in 1993. Again, this one of the real floppy disk drives with a decent build quality and high reliability. Similar to the other floppy disk drives that I am using with the 80386-based computer, the front face is a bit on the gray side. As a particularity, this drive is made in Japan. The other two FDDs are made in Malaysia. There are no visible quality differences between them.

This is the underside. The same construction style as shown on above. This unit has an amber front LED.

This CD-ROM is a four-speed SCSI drive made by Toshiba in 1996. The exact model is XM-5401B. It has a grayish front face that matches the floppy disk drive. But it is way off the white color of the case.

Human Interface Devices

I decided to use only one CRT monitor and one keyboard to control both machines, since I don't have too much space for a lot of computing hardware. For this to happen, I have sourced a very cheap KVM switch from eBay. After some quick maintenance involving replacing old electrolytic capacitors, I had a working switching unit. Unfortunately, the switch came without connection cables and in the end, these were more expensive than the switch itself.

Here are the HID peripherals that I am using with these two computers.

I also have a very nice 17" EIZO CRT monitor, but it developed a defect lately. The screen displays a reddish tint after a couple of minutes after powering the monitor on. I hope I will be able to fix this issue at some point. Until then, I won't use it at all.

Conclusions and Reflections

It took me a long time (in fact, in the order of years) to build these projects. Even though I designed the schematics and PCBs for all the projects in less than one year, the knowledge required for this was acquired during many years of hard-working, learning, experimenting, and so on. I also started raising funds for this a long time ago, since I knew it was not going to be cheap. However, if I were to buy every component from eBay, including shipping and possibly import duties, the price tag would've been on the high side as well. But there wouldn't have been the fun part.

But in the end I managed to get almost all the important pieces working together. Hopefully everything will be good once I will address the remaining issues.

Copyright © 2004- Alexandru Groza
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