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> The MS-DOS Machine |
| The MS-DOS Machine Good old DOS. I used to use DOS a lot back in the day, up until Windows 95 came out. It was probably the best operating system ever for games. The hardware back then was pretty limited, so the high quality graphics of some DOS games are that much more amazing. I recently found myself wanting to go back and revisit some of those games and applications I was so fond of, so I decided to build my own DOS machine. Hardware So, finding the hardware was nothing hard. Modern hardware tends to behave a little unpredictably with DOS, which is why I chose not to install it on my do-everything workstation, which is already hosting three operating systems. Old computer hardware is pretty much everywhere for free, sometimes people will even pay you to take it. In fact, I already had a couple of older computers laying around doing nothing. One was an Acer, with 16MB of memory and a Pentium Overdrive processor running at 60 MHz, from 1993, and the other was a more expensive "Vektron" with a 100 MHz Pentium and 32 MB of RAM, ca. 1994. Neither one of them had any interface cards, but each had seven slots, three PCI and four ISA. I ended up using the Vektron system, since I kept having trouble with the Acer and its configuration settings. It uses one of those Dallas real-time clocks that has the integral battery, so it loses its configuration data every time you turn it off. There's a four pin header on the mainboard that says it's for an external battery, but it doesn't say which are the positive and negative leads. The Vektron has some battery issues as well; it was left out in the rain for about a week which caused some internal trace in the mainboard to corrode, so it doesn't keep its config settings either but it still boots OK. Probably the most important part of this machine would be the sound card. Modern soundcards are pretty much all awful, in that for the most part they don't have built-in synthesizers. Fortunately I have a very old ISA soundcard, an Acer Magic S20, from 1991. It uses a Crystal CS4234 CODEC, and a Yamaha YM262 FM synthesizer. Crystal makes great DACs, but the synth part is really special. Most keyboards, synthesizers, and software MIDI players these days use wavetable synthesis, where samples, extremely short recordings of an instrument are looped to create a note. FM synthesis, on the other hand, works by daisy chaining together oscillators. The oscillators can generate square waves, sine waves, and sawtooth waves of varying frequencies on their own; to get more complex waveforms the output of one oscillator is used to drive one or more other oscillators. The sound produced by this process usually isn't as "realistic" as wavetable synthesis, but it has more of that classic, chirpy, sound chip sound characteristic of old video games and a lot of music from around 1979 to about 1994. The video card is an old Diamond Stealth 64+ PCI card, which uses an S3 Trio 64+ graphics core. I don't know a whole lot about it, but I think it has 1MB of graphics memory. It also has various header connectors with cryptic labels like "MPEG Feature Connector" that I have no idea what to do with. One MB of graphics RAM might not sound like a lot, in comparison my desktop has 2048 MB, but it's way more than enough for most DOS games, some of which were designed for systems with half that amount of main memory. I think the mainboard on this system is pretty neat. For one, it was made in Ireland. How often do you see anything made in Ireland? How often do you see anything electronic made outside of Asia? As I mentioned before, it has plenty of expansion slots, three PCI and four ISA. It also features two IDE channels, two serial ports, a parallel port, and two memory banks that can accept up to around 64 MB of RAM. I'm using 40MB, supplied by two 16MB fast page mode SIMMs in bank 1 and two 4 MB EDO SIMMs in bank 0. I had a few larger RAM chips, but the downside of SIMMs is that unlike todays DIMMs, they have to be installed in matching pairs. The floppy controller on this board is worth mentioning. It's a National Semiconductor PC87306 super IO chip. I have one "vintage" computer that uses floppy disks not common to the world of PCs, and I might end up with a few more eventually. The BIOS natively supports 1440kB and 720kB 3.5" floppies as well as 360kB, 720kB, and 1200kB 5.25" floppies, which is a good thing. The Image Disk program developed by Dave Dunfield is capable of using a PC to write floppies for a variety of really old computers, including the 8" floppies that are pretty much non-existant today. According to his database of tested floppy controllers, the PC87306 is one of a very few that passed all of the tests on all of the different types of floppy drives. The Software I wanted MS-DOS version 6.22 as the main OS, but I'd also like to have Windows 95. A machine this old doesn't really like to dual boot, so I came up with a better idea. Instead of using hard disks I'll use flash cards. Both MS-DOS and Windows 95 require very little space, so they wouldn't even have to be very big cards. That way when I want to switch operating systems all I have to do is eject one card and pop in another. It will also simplify transferring files, since I can just plug the card directly into my desktop instead of going to the trouble of writing files to a floppy disk. Getting the cards set up was a little convoluted, and also a pain in the ass. For some reason none of this old hardware has any kind of a keyway or blocked pin to let you know which way the interface cable should go. If you get it backwards the mainboard won't even POST. A simple trick is to look for the tiny dot, arrow, or number 1 on the mainboard that indicates pin 1; the cable should be plugged in so that the red stripe is on that side. I have my cards plugged in through two adapters, there's a 40-pin to 42-pin desktop to notebook adaptor, then a notebook hard disk to CF card adaptor plugged into that. The interface used on CF cards is essentially the same as ATA, so the adaptor is pretty much just physical, there isn't any active circuitry other than a voltage regulator. What this means in the end is that all of this hardware is really cheap. The cards themselves are nothing special. The one I used for DOS is a 64 MB Lexar CF card that I bought for about $40 way back in 2001. The other one, for Windows 95, is a new San Disk 8GB model that cost about $20. There's not much sense in spending extra money for really fast cards, since the interface used on this mainboard would probably have to fall back to a lower speed anyway. Installing DOS This is pretty much the easiest operating system to install eve. There are only three floppy disks, you just boot off of the first one, it asks you a few questions, formats your drive, then prompts you when you need to insert another disk. The whole process only takes a few minutes. Installing Windows Windows is a little more complicated. The setup menus are actually pretty similar at first, but then it goes to a graphical screen where it asks you for things like registration information, time zone, whether the machine will be connected to a network, etc... By far the longest part was waiting for the files to copy over. I have the floppy version of Win95 for some reason. It comes on 13 floppy disks, 11 of which are formatted weird, so that they hold 1.68 MB instead of the usual 1.44 MB. Microsoft calls this "Distribution Media Format". I actually have no idea what happened to my original Win95 disks, so all I have were disk images. I had a hard time writing them to disks because of the weird formatting. The only program I found that would work was the shareware program WinImage, and even then I had to select "Format and write disk", which incidentally takes forever, for every single disk, even if it had been formatted before. If you're going to go this route I suggest using good quality disks fresh out of the box, things will go alot quicker and more smoothly. I actually did this with just two disks, I'd write one, put it in the machine I was installing it to, write the other, swap them, overwrite the first one with the next image and so on until I had all of the files transferred. I guess the only problem with this method is that if it prompts you to insert disk number x later on you'll have to write another one. |
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