The Epilogue of My 486 DX2-66 Build

I remember that day like the back of my hand. The day my friends replaced their 386 DX-40 with a 486 DX2-66. I couldn’t wait to go see it! We were over at my grandparent’s place and I was begging my parents to take me over there. It almost didn’t happen, but persistence paid off!

That night, over at their place I remember the 17″ monitor, showing off Norton Commander the biggest I had ever seen it. They were copying some files around and man that baby flew! We still had our 386 SX-16 at this point and I remember thinking how duddly it was in comparison.

I spent so many days over there, I can’t even count them. This was really the one system that portrayed for me the beauty of the MS-DOS era. 1993 at it’s best.

Us, going from our 386 straight to a Pentium-100 was nice, sure! But looking back I definitely always felt like a missed the sweet spot, so a couple months back when I stumbled across a 486 motherboard at a thrift store I knew it was my opportunity to finally put together this classic rig of the golden era of pc-gaming… and wow, have I learned a lot. This has by far been one of the best times I’ve had with a build. Lot’s of challenges, changed plans and ideas. In the end I couldn’t be happier and it’s turned into my retro PC daily-driver (for the time being).

Here is the board I found-

Yes, it has a SX-25 chip on it. Pretty cool chip, and was useful enough for making sure the other components I had laying around worked while I awaited the golden DX2-66 to arrive that I snagged for a couple bucks online.

Turns out it was quite an old board. 1989 to be exact. No cache and no VLB. It was still a 486 though and it would still run a DX2 chip!

It booted up just fine!

As expected, the battery was dead, so I replaced it.

Yes, before you yell out loud and leave, I did put another barrel battery back on the board. Primarily because I didn’t have a CR-2032 battery socket with a diode on it to use instead. I’ll keep a close eye on it, and it’s brand new, so should last a few years at least before starting to leak.

At this point I was quickly finding out how difficult it is to find AT cases (with turbo buttons and LEDs of course). I stopped by the PC recycle shop where I’ve gotten several parts for this build and they had nothing. Stopped by another, and still nothing. Some of the people at the stores didn’t even know what I was talking about when I mentioned the letters ‘AT’ in front of the word ‘case’… sigh.

I mentioned to a buddy at work that I was putting together a 486 build and was in the market for a case with a turbo button and LEDs. He said he may have one and would let me know. Needless to say, a couple days later, this baby shows up!

As you can imagine, I was pretty stoked. I quickly got to cleaning it up to shine once again-

It came with some more components an AT power supply and a socket 7 board. After thinking it over, I decided to go with a new(er) ATX power supply and use an adapter. One less thing to worry about and adapters are really inexpensive.

This also has the -5V option on it which AT power supplies provide.

The day came when my DX2-66 chip arrived. That was a good day.

I quickly adjusted my jumpers and threw it in.

Here was challenge number two- For some reason it was only benching at 50Mhz. I thought- was it a bad chip? Is this motherboard too old after all? I got to researching and in doing so learned a lot about the DX2 line, about write-back cache vs. write-through cache, about all the different releases of them, AMD, Cyrix, so on and so on…

The other weird thing is the system would actually bench fastest when I had the jumpers set to run at a 16Mhz bus, and it would get slower when moving to 20Mhz, 25Mhz, and so on.

Stumped, I finally wrote a forum post asking what the issue may be and this is where I learned about crystals and that some older motherboards used them instead of clock generator chips.

Sure enough, my board had a 50Mhz crystal on it (which suddenly made sense, considering it came with a 25Mhz cpu installed).

So, a couple days later I snagged some 66Mhz crystals-

Finally my board was benching at 66Mhz and showing the correct speeds. Yay!

In the midst of all this, another co-worker of mine also said he may have an old 486 at his parent’s place that he’d be willing to donate. Not being one to shy away from retro goodness I asked him to bring it on in! And, I’m glad he did!

The case it came in is quite cool, I would say it was an early 386 desktop-style case with a red lever power switch (perfect for a future 286 build). The best part though was what was inside the case-

An Edom International MV035 Rev. D motherboard!

Yes, you are looking at this correctly. We now have VLB (Vesa Local Bus) and cache!

After all my research up to this point, I had certainly found out that these two together could nearly double the performance of your system, even using the same CPU.

Yes, it also had a DX4-120 chip on it. I may do a build around this chip one day, but this board will still be running the DX2-66. We’re after the sweet spot here, remember. If I need a faster rig, I have my other retro PC box for that (a future post on this one upcoming).

Wow. I was stoked even more now! But… there’s more.

Holy jumper city, Batman…

When I first powered this board up, after ‘thinking’ I had the jumpers correct to run the DX2, I was wrong. I think I spent 3 evenings after work getting it right. Again, learning more and more as I went along. There was lots of frustration, but I wasn’t about to give up on the perfect platform for a rocking DX2 setup.

Needless to say, she purrs like a kitten now.

For the remainder of this post, I’ll categorize it a bit, followed by some benchmarks during various stages of the evolution of this build.


I went back and forth on what to use as a storage solution for this build. Do I want to go period-correct and stick with a HDD? Finding an IDE HDD of a small enough size that actually works is a risk and a challenge, for sure. Also, DOS rigs can only see 2.1GB drives so anything more than that on a newer drive is wasted space.

I went initially with the same CF card reader that I use in my other retro rig (Startech 3.5″ bay CF/IDE adapter), but finding a good spot to mount it inside the case was somewhat of a challenge. I realize the case is sealed up and I’m not looking at it all the time, but I’m somewhat OCD when it comes to clean builds.

This was my first go… yeah, no… This will just not do-

Time for some moderate case-modding here, I think.

I took the drive bay out and got to drilling-

Then mounted the adapter to it. It’s actually a lot more solid feeling than I was expecting!

Much nicer now!

I’m using an 8GB CF card in it and use EZ-Drive overlay software in order to get the 2GB partitions correct. It worked great… It’s nice and quiet, at least.

Something was amiss though. It didn’t feel retro enough; it didn’t sound retro enough.

While at the PC recycle shop, I managed to spot a 2.1GB IDE drive laying around. The perfect size for a DOS build. I couldn’t resist so I snagged it. After applying EZ-Drive again for a full 2.1GB partition, I ran a quick scandisk surface scan on it and there were only a handful of bad clusters. Not bad for a 20 year old drive that’s gone through who knows what in it’s lifetime.

It’s been pretty crazy how the right parts for this build just happen to show up right when I’m looking for them. Either that or the parts aren’t as uncommon as I thought. Hard to say.

I left the CF card adapter in the case still if this drive ever fails or if, by some off reason, I decide to switch back to CF (or until I need to steal it for another build).

For the other drives, I’m using a standard 1.44MB 3.5″ drive, a 1.2MB 5.25″ drive.

I initially found a 3.5″ + 5.25″ combo floppy drive, but it had suffered a violent death of capacitor leakage and wouldn’t react to electrons at all.

For optical, I’m using a Creative 24X CD drive.



Deciding which graphics card to use was my next biggest question. Sure, I could just throw anything in there, but I wanted to play Doom on this box still, and have it be playable. I mean, what’s the point of having a 486 if you can’t even Doom it out a little, right?

More research time.

One of the biggest contributors to my knowledge of these systems is Phil, from Phil’s Computer Lab. His videos are great and he has a lot of useful information and utilities available for retro systems.

He did a couple videos comparing several lines and models of graphics cards for a 486 and I came to the conclusion I would be in the market for a Cirrus Logic CL-GD5429 card. Initially I picked up the ISA model for my first motherboard since it didn’t have VLB, but then managed to find a CL-GD5428 VLB card as well at the recycling shop. Since the 5428 and 5429 are very close in the benches, I went ahead with it.

This VLB card increased my system speed and bench results by a solid 50-60%. as compared to the ISA model (more on this later).

I tried out a few games though and my smile turned around 🙁

Something was wrong with the card unfortunately. There were strange vertical lines when running any games or applications, and Windows 3.1 would have weird glitches here and there.

I tried different VGA cables, different monitors and even re-seated the chips and re-flowed a bunch of the solder pads. Still the same result though.

Oh well, back on the hunt for a replacement, as this would just not do!

I managed to find an actual CL-GD5429 VLB card online for a good price and snagged it up! It benched even better and the 5429 chip was what I was after in the end anyway!

Here are the ISA and VLB versions of the cards-

I love that this VLB card also has sockets to add extra ram, so I quickly ordered some of that up as well, to up it to 2MB (yes, that was a lot 23+ years ago).

As I’m sure you’ve noticed by now, this build has been an evolution in progress though, and my buddy at the PC recycle shop had a box of sweet items for me. I ran by there during a lunch break and wouldn’t you know it…

An Tseng ET4000/W32 VLB card sitting there, begging to come alive again.

I couldn’t believe it… This was one of the few cards that could actually beat the CL-GD5429, by quite a fair margine in fact and considered by many the best performer ever on a VLB system! This model doesn’t have any slots to upgrade the 1MB of RAM, and I searched for hours for the make/model of the card to find out the jumper settings, but with no FCC-ID or model numbers, I couldn’t find anything. I’ll still be adding the additional RAM to the CL-GD5429 card to see if that makes any difference, but for now, this is quickly turning into the dream DX2-66 build, one component at a time.



I assumed initially that 72-pin RAM would out-perform 30-pin RAM, so I tried both to find out. Turns out they bench exactly the same. Confused by this, I did some research and verified the two specifications are in fact the same and there is no difference in performance. Since I only had 8MB of 72-pin and 16MB of 30-pin, I went with the 30-pin here. I know 8MB is plenty, but why not use 16, if I have it, I figured.

As for cache, this motherboard supports 512K, so I couldn’t resist seeing what kind of difference it would make, considering how much the initial 256K made. I snagged some chips and set the jumpers as per the manual and quickly got to benching it. It wasn’t an astounding difference, overall (again, more on this later). Certainly not as much as I was expecting, but such is the law with computers, there is always one bottleneck somewhere. At this point, it is likely becoming the CPU, which is exactly where I want it.



I initially had a Yamaha Audician 32 Plus card in here which is a nice card when using systems with external midi devices, which I will be doing. Mostly because of the on-the-fly IRQ and other adjustments via software, and the Yamaha OPL3 chip.

I noticed I was starting to have issues with this card though. King’s Quest V, for example would only work with IRQ 5 and King’s Quest VI with IRQ 7. Yes, I could just switch them before playing each game, but the more I though about it- it’s not a period-correct card and didn’t feel quite right. In one of my boxes of goodies from the PC recycle shop, I happened to obtain a Sound Blaster CT1740. Initially I thought I would have to adjust the IRQs with jumpers, which is true yes, but I figured it would be worth a shot to try anyway as I certainly don’t recall ever having to do so when playing games on any of my rigs using Sound Blasters growing up. The other nice thing about the CT1740 is it also has an OPL3 chip so no issues with midi devices. Bonus!

I tried it out and it works perfectly! No IRQ adjustments needed! I went ahead and installed the software and drivers for it, but quickly removed most of the extra bloatware it added to my autoexec.bat and config.sys files, which took up 35K of conventional memory.


Display, Midi, KVM-

Since, my retro cave isn’t considerably large by any means, I don’t have room for multiple CRT monitors for multiple rigs, especially since I snagged this beauty, brand new from the PC recycler for $10 with a mix of other parts-

(Sony Trinitron 19″ flat-screen)

There is no way I’m setting up retro rigs on LCD panels. I don’t care if this CRT barely fits on my desk, there is no comparison to the authenticity, the retro-ness, and the clarity of a CRT for DOS/Win 3.1 gaming (not to mention refresh rates).

I needed a way to be able to attach both of my retro PC systems to the same monitor, keyboard and mouse, so I picked up a cheap KVM that supports VGA and PS2, and it works great!

I was also looking for a way to attach both of my systems to my MT-32 and SC-88 midi modules. This was as simple as grabbing some cable splitters/adapters and hooking it all up.

At this point, I can essentially have both of my PC systems powered up and switch between them at will. It works out pretty good.

Again, I’ll soon be putting up a post on my ‘other’ PC retro system I keep referring to. Stay tuned for this.

Final thoughts, conclusions and benchmarks-

Here are my current benchmark results at various stages throughout the evolution of this build- (this chart is interactive. Hover your mouse over it to see numbers)

I took quite a bit of time with cable management on this build. Much of the cabling is on the backplate behind the motherboard. I didn’t really want a huge mess of cables everywhere, so here’s how it turned out-

What a beauty, eh?-

Overall, I am extremely happy with this rig. I’m even more happy to have finally built a 486DX2-66. What a joy it was and I learned so much in the process. A big shout out and thanks to Vogons members, Phil from Phil’s Computer Lab, Clint Basinger, Rusty and Erik from my favorite PC recycle shop- Recycle Techs, who have put up with me stopping by all the time looking for ISA boards and the like. And of course to my friends the Bensons, down the road who got me hooked on this system and were the inspiration for me doing all of this in the first place.

Final specs-

Edom MV035 Rev. D Socket 3 motherboard
Intel 486DX2-66 processor
Sound Blaster 16 CT1740
16MB 30-Pin RAM
Tseng Labs ET4000/W32 Graphics Card
3.5″, 5.25″ floppy drives
24X Creative CD-ROM drive
Sony Trinitron 19″ Flat-Screen CRT
MS-DOS 6.22 / Windows 3.1

Roland CM-32L
Roland SC-88vl
And of course, a Gravis Gamepad!