VOGONS


First post, by ockiller

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Hey all!

This is inspired by the work of TheRasteri on the mini DOS PC and the weeCee projects (here is his topic if you happen to have missed it). Thanks a lot for making me discover a lot on the world of embedded industrial computers, I didn't know much about PC/104 and wasn't even aware of the existence of the Vortex86 line !

I already investigated on the subject of MS-DOS compatibility with modern hardware, I know all of the quirks, the declining support of the legacy graphics modes, etc, and the toughest of all, the Sound Blaster compatibility. I concluded that you had to rely on >20 years old hardware to run DOS games with sampled sound, and was pretty sad it would only get more and more difficult and expensive to get rarer and rarer compatible hardware. So I was surprised to see that x86 PCs with ISA bus are still produced and can be bought brand new. These Vortex86 boards/modules are incredibly capable of running games from a lot of eras (probably better than a regular PC), with great magnitude of CPU speed settings, the VESA 3.0 adapter, the ample enough resources to run Win98SE without breaking a sweat. They are already "dangerously close to my dream devices", and although they are not cheap, they are not that expensive either (~the cost of a new modern PC...).

The only missing thing is the Sound Blaster compatibility, hence TheRasteri awesome projects. But I wanted to explore this path but with an approach that is more friendly for those like me who find assembling and soldering too daunting. So I wanted to assemble my retro PC from parts that are still produced to this day, that are easy to find, and cheap. It seems to be one of the first ideas of TheRasteri as he mention this in the beginning of this video. So yeah, the idea will be to build a regular case, with an existing old ISA sound card. Yes, it still relies on old used hardware, but I like the fact that it considerably reduce the problem as we don't have to rely on old motherboards, CPUs, RAM, graphic cards, (etc ?). And, projects like the Orpheus exist, so it's possible to build an all brand new retro PC...

Mmmh, how geeky that looks...

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Yeah, screaming all of it's OPLy Grabbag

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Even if I haven't entirely succeded, I'm happy of the result, and I want to share my experience for those who want a bulky weeCee clone (ugleeCee ?).

First, the Vortex86 PC/104 products from ICOP are good candidates, as they contain by themselves almost everything you need to run old games (CPU, VESA 3.0 graphic adapter, RAM, USB, PS/2, IDE, LAN, Serial/Parallel) and are easy to power (5V only, many options, including a simple molex plug). As PC/104 Sound Blaster compatible sound cards are not an option, there are two ways to get ISA ports. An ISA to PC/104 adapter, which seems to be very easy to make, but expensive to obtain (100 $/€...). I could get away for cheaper with an ISA backplane, with the added benefit of easily providing the +/-12V required by ISA sound cards from an AT power supply. Some backplanes can take an ATX power supply directly, but ATX->AT converter cables exist. If you can, take an adapter with the green/black wires to plug a "hard switch", otherwise you will have no convenient way of shutting down the PC (or a multiplug with a switch?).

Some backplanes can take directly a PC/104 board, as seen in this topic. I took the route of "half-length single board computers", which look like ISA daughter boards. It can be plugged as is in a backplane, along with any number of other ISA real daughter boards. The exact model I chose from ICOP is the VDX-6324RD-FD. I recommend going with a DX/DX2/DX3 as they seem to be the more powerful options (avoid the SX with no FPU). Not too much RAM as it's known to cause trouble to MS-DOS and some Windows 9x. This board also includes a floppy drive controller with the appropriate header (thus the "-FD"), sadly this one and the IDE header are smaller than the standard PC headers (2mm pitch instead of 2.54mm/0.1"), and require special, hard to find ribbon cables (they seem to be provided if bought brand new). The IDE adapters are reasonably hard to find, but for the floppy cable, I suggest building one from jumper cables...

These Vortex86 boards/modules don't like USB mice, so you have to find a PS/2 mouse or a USB one that handle the PS/2 protocol (compatible with a passive converter). No problem with an USB keyboard, and USB mouse work correctly under Windows 98 SE. These boards only have a VGA D-sub output, and it's a problem on its own if you don't have a VGA input any more on your monitor. Consult this topic for more information.

Then, for the case, I guess most backplanes use the AT screw holes locations. Some are common with the ATX form factor, it may be sufficient, the daughter boards will also help adding more rigidity, but it may not be ideal. You will need an ATX case with front USB ports, that's the easiest way of using the USB header ports of the board, but beware, these USB headers are not located at the same spot as they usually do, they require a longer cable, and those of your case may be too short! That was the case for my old unused cases, so as you could see, I have no case at the moment 😀. I still harvested the front ports with their cables, along with a crappy old ATX PSU.

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On the storage side, I bought a SD card reader on IDE (small board presently shamefully dangling behind the desk), but you are free to go any option, even add a CD-ROM drive (not tested). That way, you can setup your computer like any computer of the era, including TheRasteri's way.

And last but not least (the whole point actually), the sound card. The only part that you can't easily find new. I had a couple left in my attic, an AWE64, and a Yamaha YMF719s based. I chose the later as it seems easier to configure, and is smaller. Don't judge me, I know some value the AWE64 way higher than the Yamaha, but both have OPL3 synthesis, and my ears are not OPL experts 😀. Nothing to say except that it's working as it should \m/.

On the performance side, my BIOS doesn't allow going below 100 MHz (486 level performance), but we can still disable the caches (286 level performance). That's still too fast for some PC/XT games. The maximum it can reasonably run are games like Tomb Raider/Quake, at around 15/20 fps at 640x480 (~300 MHz Pentium, as TheRasteri and LGR mentioned). It has no 3D acceleration and no possibility to add it. You would need boards that also handle PCI (I haven't investigated that path, but it seems possible to build something similar with a real Voodoo).

Up to that point, this project cost me ~200 €, I bought the Vortex86 SBC used on ebay, along with a backplane, and I harvested many things I already had (PSU, ISA sound card, VGA screen, keyboard/mouse). Yeah, wanting to buy used parts that are still in production, does that make sense? Yes to me because as there is still a market for those parts, there is no reason the source of used parts will dry up soon. And I love the idea that the future of native MS-DOS retro gaming is not as dark as I thought 😀. But yeah, for the same money you can build a far more powerful PC, still with maximum compatibility, or go emulation for free (but at a slower speed), I even have a hard time to justify the interest of this, apart from that it's fracking cool 😀.

I still want a case for this build, and with my 6 ports backplane I can't get away with a µATX one, so I will end up wasting a lot of space. That space would probably help me screw the SD card board somewhere, I don't know. A case with an easily changeable power button will also be nice (no soft-OFF). And I also haven't seen any header for the power ON LED nor the disk activity LED on the SBC.

I hope I got you interested, and I will be glad to discuss about even better ideas, answer your questions, etc.

Last edited by ockiller on 2021-12-08, 12:59. Edited 2 times in total.

Reply 1 of 3, by janih

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Great stuff. I've got a Celeron 400 based pc104 board and a 386sx sbc and a ISA backplane waiting for something like this.

Maybe I'm going to make a small dos pc with an ISA > PC104 adapter: Cheap Homebrew ISA->PC104 adapters or just use the ISA backplane that I have.

Reply 2 of 3, by Hezus

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Very cool! 😀 I applaud these kinds of developments, although at this point buying a used 486 or pentium is still a lot cheaper than going to Vortex86 route. Let's hope it'll stay that way for a bit longer 😉

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Reply 3 of 3, by ockiller

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@janih: I didn't know about the old Intel PC/104 boards. Your Celeron seems to be a Tualatin core, the last desktop P6, cool stuff! And if you can also expose the PCI ports, you could plug a Voodoo too 😀. The 386 SBC seems to be the ancestor of all the Vortex86 things, and I like the possibility to plug old floppy drives.
I recommend using a backplane instead of an ISA adapter, the SBC is likely to only use 5V, and won't provide the other voltages to the daughter cards. The backplane offers a convenient way of providing all the different voltages (except the -5V, which is rarely used).

@Hezus: Totally agree, it's cheaper and has much less hassles to go with old used standard PC components. The non standard headers for IDE/FDD is a pain if cables are not provided. There are no IDE drivers for Win9x so it uses real mode / compatibility mode. But as I said, it's kind of a "for science" project, I dreamed about a "686 NuXT" PC and this is the closest I could get, thanks to TheRasteri's inspiration 😀