Anatomy of a Pentium based DOS PC

A lot of people are intimidated by DOS. I was one of those people, I grew up with a commodore 64 and a Amiga in the household so by the time I had a PC it was well into the Windows 95 era. Hopefully this article will help dispel a few myths about the difficulty of setting up a DOS based PC. I am also aware of DOSBOX which is a DOS emulator for use on windows machines and although sometimes emulation is a great way to play games that otherwise may be unavailable it’s still my opinion that it’s no replacement for the feel and nuances of the real deal, even with the latest versions of most emulators I still sometimes find errors in speed and sound. but to each his own I suppose. I’ve created a quick reference page for various PC slot and port types if needed

The easiest, cheapest and all around most compatible DOS PC to put together in my opinion is an early Pentium based system. The one I have assembled uses slightly more expensive parts in an attempt to create an “ultimate” Pentium based DOS machine and perfect for more late era DOS games from the mid 90’s. Usually you can find these older PC’s for cheap at flea markets or yard sales. I found mine for $5. usually they come with windows 95 but that can easily be formatted and replaced with DOS.

this is a typical mid to late 90’s PC case. they loved off white and beige back then.  Has your standard power button, reset button and sleep mode button.

Here’s a rundown of the parts inside. You’ll most likely have these (of some sort) if you picked your PC up at a sale.

1) motherboard, this determines the connectors, CPU’s allowed, max ram and all that good stuff. Mine is a socket 7 board which supports a range of Pentium 1 and AMD CPU’s. You also want to have at least 1 ISA slot (you can easily look up slot types on Google or Wikipedia) since DOS loves ISA slots for sound. My board here has 1 AGP slot 4 PCI slots and 2 ISA slots so its great for my needs. The one I’m using here is a PA-2013 which from what I’ve read is one of the faster socket 7 motherboard produced. It also comes with a massive 2mb of onboard L2 cache memory.

2) power unit, my motherboard has a ATX power connector which are very common but some of these early boards may have an AT power connector which are a bit rarer. you can also snag a ATX to AT power adapter off of eBay for a few bucks.

3) standard CD-ROM drive, you can use a DVD drive but there’s not many if any games from the DOS era that use DVD’s

4) 5 1/4 floppy drive. not really needed since this computer is going to be to fast for a lot of really old games and most DOS games from this era came on 3 1/2 floppy disks or CD anyways.

5) 3 1/2 1.44MB floppy drive.

*Not in the image above I recently installed a 100MB Iomega Zip drive in the bay below the 3 1/2 floppy drive. The zip drive runs off the IDE bus just like the CD-ROM drive. My late socket 7 Motherboard can recognize the drive in BIOS but for operation in DOS it requires drivers and is seen as drive F:. The ZIP drive is convenient because I’ve found there are a lot of files that are just to big to fit on a 1.44MB disk but are not worth burning onto a CD so the ZIP drive is a great and convenient middle ground.

6) Hard drive. I believe DOS 6.22 has a limit of 504MB without using partitions or any other tricks though FAT 16 format can read up to 2GB hard drives on one partition. certain BIOSes can support 2GB partitions though in DOS such as the BIOS on this motherboard. That’s still a lot of space since a lot of games and applications from this era are pretty small. larger drives will work no problem but the OS will only see 504MB or 2GB depending on your BIOS. The first drive I have installed is a 10,000 RPM SCSI drive. SCSI drives tend to be faster and more reliable then IDE hard drives but usually harder to find and more expensive. I believe I have a 8.5gig HDD installed though my OS only can “see” 2GB which is more then enough.

7) This is my secondary hard drive or drive D:\ which is connected to the IDE bus. It is slower then my primary SCSI drive and was formally my primary hard drive. I kept it in my machine after upgrading to SCSI as just a backup and extra space.

8) CPU, I have a 200mhz MMX Intel CPU installed. In my opinion it’s a little to fast and I would recommend something more along the lines of 100 or 133mhz CPU. as you go back and play older games your going to hit speed issues with any Pentium class CPU but anything faster than 200-233mhz and you could start seeing more timing and speed issues showing up in even some early 90’s games.

9) RAM, i have a 128MB stick installed. its a bit of an overkill. most games of the era would be more than happy with 64MB or even 32MB and less

10) cheap extra 99 cent slot fan i grabbed in bulk of eBay. not needed but it helps cool and we wont be using the AGP slot (although DOS should still run fine under an AGP card you may not have as much compatibility since newer cards don’t always support older video standards and resolutions)

11) SCSI controller card. You can also go with SCSI if you add a SCSI controller card. Using quality SCSI controller cards and high end SCSI hard drive/CD-rom drives can increase PC performance since SCSI is less taxing on the CPU. It also makes it easy and convenient to add multiple drives in the future via the external SCSI port available via the SCSI card. Using SCSI hard drives can also overcome the HDD size limit sometimes. On later machines like this one the performance boost is less pronounced then it would be on a 486 or lower but the option to add more external drives still makes it worth wild. I installed a PCI Adaptec AHA-2940w/uw card in the machine as well as a 2GB SCSI hard drive to compliment my IDE hard drive.  This card is well supported and has both external and internal 68 pin connectors as well as an internal 50 pin connector. I added a 8.5GB SCSI (seen as 2GB) IBM hard drive in this system to compliment the IDE Maxtor 9.5GB just to add more space and to test out the drive. using the speedsys utility my speed rating for the IDE drive is 424.81 while the SCSI drive is rated at 819.85 which is almost twice as fast as the IDE drive. I eventually may just go all SCSI with this setup.

12) graphics card, I’m using a S3 Trio64V2/DX PCI card. These cards are not very expensive, fairly powerful and were widely supported in the late DOS era. There is a very wide variety of graphics cards you can use for this era but in my opinion the Trio64v2/DX is the card for the job. There is supposedly a version of the Trio64V2 that uses faster SDRAM labled as a /GX but I have never run across one. You can also use a ISA graphics card but they are generally slower and not as capable. Some motherboards will come with on-board or built-in graphics chip. Generally these aren’t as powerful as buying an add on card. sometimes just installing a add on card will override the on-board video but sometimes you may need to disable the on-board in BIOS.

*After some debate I decided to upgrade my PCI video card to a S3 Virge/GX like this one in my “Building the best all around DOS computer” article.

It has the same 2d core as this Trio/V2 but also more Ram and the ability to run “accelerated” S3D DOS games like Terminal Velocity. Its a really minor thing and any DOS machine will be fine with a trio but I had an extra Virge on hand and decided what the heck.

Also when using either the Trio or any Virge I discovered a utility called S3VBE20. Do a Google search and it should be findable. Its a TSR DOS program that will update your S3 cards VESA from 1.2 to 2.0. This will help when running some games in SVGA. For example it will allow you to chose from many more resolution options in a game like Quake (though if you can actually run the higher resolution modes at a decent frame rate is another matter).

13) 3DFX Voodoo 1. You can also add a Voodoo 1 3d card to this setup. it is a PCI 3d graphics card that you can install in a slot next to your main 2d card (like the Trio64v2). you will need a short VGA cable to externally connect the Voodoo to whatever 2d graphics card you have installed. there are actually a few DOS games that support the Voodoo 3d accelerator card (Carmaggedon, Extreme Assault, Tomb Raider, Ect…). I use a righteous orchard voodoo 1 card with 4MB of RAM. This card uses a mechanical switch so there is an audible “click” when the voodoo activates for a game which has no practical effect but I like it. I recently added this card to my setup so its not in the numbered internal pic located above.

It should be noted that all but one Voodoo 1 cards have 4MB of RAM. Canopus sold a version of the Voodoo called the Canopus Pure 3d and its the only Voodoo 1 card to use 6MB of RAM as well as a TV out. Good luck finding one though as there pretty rare.

14) sound card. For my sound card setup I went through several options before settling. There really are many ways you can go. For this setup I am currently using a sound blaster/daughterboard combo. The current combo I have installed is a Sound Blaster AWE32 paired with a NEC XR385 For the general midi. The AWE32 is backwards compatible with the Sound Blaster 16. The daughterboard is a NEC XR385 which is a NEC relabeled Yamaha DB50XG. These cards are relatively cheap and when attached to a sound cards wavetable header give General Midi support. The general midi standard of the time was set by Roland but I actually prefer the Yamaha general midi sound for certain games and some even specifically support it (Extreme Assault). The sound is mostly the same as the Roland general midi but In certain games like DOOM I think the Yamaha GM sounds better. My particular model lacks a Yamaha FM chip for accurately playing FM tunes in older games but for the era this PC was created for most games will be using general MIDI or CD audio anyways. There are models of the AWE32 that do have genuine FM chips though if you lack a separate PC for older DOS games where you may want an accurate sounding FM capability. I have 6MB of RAM added to this AWE32 but with the superior GM daughterboard you’ll really never use the cards own midi.

AWE32

AWE32 with NEC XR385 daughterboard attached

Formally I used a Sound Blaster 16 model 2900 paired with NEC XR385 giving me good FM synth and SB16 compatibility. The big issue with this card is the “hanging note” bug that effects almost all SB cards. The degree of the bug varies from card to card but basically it created hanging or stuck notes when used in conjunction with a midi device (either external via the midi port or internal via the waveblaster header). my particular card works pretty well with some games but I get the error with others. Heres a clip taken from DOOM, you can here the hanging note bug as a high pitched “twinkle” sound that should not be there. Listen closely and you can hear it at 0:02, 0:07, 0:13, 0:34, 0:35 and 0:53 in the video here. This card was particularly bad with the “hanging notes” and made games like Daggerfall almost unplayable. After switching to the AWE32 I got the bug far less. In DOOM I’ve only heard it once so far and it hasn’t reared its ugly head in Daggerfall at all yet.

A simple alternative would be to use a Sound Blaster clone card or using two sound cards, one for MIDI and one for digital sound effects. Rather then dealing with installing two cards though I decided I can handle the occasional issue with the AWE32. I did attempt to use a clone card pictured below. It is a Audio Excel card. Unfortunately It failed to install on this computer for unknown reasons. I did manage to install the combo on a separate Pentium DOS PC where it performed fine with no “hanging MIDI” bug. Note though that this card lacks the Yamaha FM synth chip so FM sounds off. There are also reports of some games that just are not compatible or that sound “not right” when running as a Sound Blaster.

Now that all the parts are together there’s a lot to do. You should reformat the hard drive, install DOS (i strongly suggest DOS 6.22) and then install the mouse driver as well as the sound card driver. Most of the motherboards from this mid to late 90’s era should auto detect the hard drive, CD drive and floppy drives. You don’t have to but you may want to replace the CMOS battery. This is a little battery that remembers your settings and the date/time. It’s the same kind of battery they have in a lot of watches but a little bigger. Its cheap and easy to swap out. DOS should be available over the internet if you look hard enough or you can buy a copy online. Sound card drivers should be out there as well. Generally drivers are not required by DOS for graphics cards.

I also use dos navigator 1.51 which can be found for free. it’s a dos navigation program that makes looking around for files in DOS more “windows like” but it should not interfere with DOS compatibility at all. Be aware if its running it does eat some conventional memory.

on to memory. a lot of people have bad memories of running DOS because of frequent memory issues. some games, especially from the late DOS era that our computer is aiming for require large amounts of conventional memory. even when I was a relative newbie to DOS I have to say I ran into very few issues with making conventional memory free. some people say not to run it but if your running DOS 6.22 run the memmaker program and it will optimize your memory. usually that alone gives me almost 600k of free memory. there are a lot of tricks I won’t cover here but just look up how to optimize conventional memory in DOS. load as much as you can into high memory. lean how to manipulate the CONFIG.SYS and AUTOEXEC.BAT files with the EDIT command. one trick to free 1-3kb or more is to change the lastdrive parameters in the CONFIG.SYS file. usually its set to Z but your most likely never going to have that many drives so set it to something more reasonable like H. here is a pretty good but somewhat technical site for optimizing RAM in DOS http://www.mdgx.com/mem6.htm

I achieved 617k conventional memory with very little effort. that’s enough to run just about any game including Elder Scrolls: Arena, a huge mem hog.

I would say with a little looking around a setup close to this would cost less than $50 even less than $20 or free if your lucky and ask around. it’s most likely a little to fast for really old DOS games but offers good overall compatibility and the ability to play demanding late era DOS games at top speeds and visual settings.

Here’s a video I did on this machine.

Here is the sound setup I used prior which was an AWE32 you can listen to compare

*Updated image with the ZIP drive installed and the upper drives slightly rearranged.

Benchmarks

Pentium 200mhz MMX, 128 SDRAM, 1MB L2 cache, 4MB Virge/GX PCI

3dBench – 152.2 FPS

PCPBench – 60.2 FPS

DOOM – 81.54 FPS

Quake – 48.3 FPS

Landmark 2.0 – cpu – 1312 fpu – 3486 video – 24576