486DX2/80 Build - When You Have Lemons, You Make Lemonade

I mentioned in my 486 Pentium Overdrive blog post that I had gotten a 486 motherboard that did not work out for that project. The motherboard had actually come out of an arcade machine from a company called Lazer-Tron. There was no documentation to be found, so finding jumper settings for the CPU would be a next to impossible task. I put the motherboard aside thinking I probably was not going to use it anytime soon. Time passed and I was doing some reading on Cyrix CPUs. Cyrix did not manufacture their own processors, they contracted IBM, Texas Instruments or SGS Thomas to do that. Part of the licensing for these companies was that they could produce these CPUs under their own branding. So if you see a 486 from one of these 3 companies, it's really just a Cyrix 486. That motherboard came with a SGS Thomas 486DX2-66. I had Cyrix 486DX2-80 from another project. While I could not change the jumpers for the CPU, the jumpers for FSB speed and voltage are silk screened on the motherboard. A light bulb went off when I realized I only needed to change the FSB speed from 33MHz to 40MHz. The motherboard was already configured for Cyrix 486DX2 CPU! 

I had everything I needed already laying around except for a case. I looked on Craigslist, but there was nothing to be found locally. I went on eBay and to my surprise I found an AT case with with a 1.44MB floppy and CD-ROM for only $25 plus shipping. I immediately purchased it. When I got it there were some scratches on the case, but nothing a new coat of paint won't fix. I assembled the system and pressed the power button for the first time. The lights came on, but the system would not post. After some diagnosis, I came to the conclusion the power supply was not working. Luckily I had some spare AT power supplies on hand. I grabbed one and tried it. The system came to life, but then another problem arose. The system would not always post. About once in every 3 times I powered it on, the LED lights were on, but that was it. Pressing the reset button would get it to work. I cleared the CMOS and that fixed the issue. There must have been some corrupted CMOS data. I finally had a working 486DX2 system from a motherboard that I had pretty much written off. There a couple of minor annoyances with this system.  The motherboard does not have an IDE LED header and the case lacks a Turbo switch, but I can live with these minor issues. The lack of an IDE LED header is mostly like due to the fact the arcade machine this motherboard came out did not use a hard drive.

Here are my system specs:

    Mustek B887 486 PCI Socket 2 motherboard with a SIS496/497 chipset and 256K L2 cache

    Cyrix 486DX2/80 CPU

    1x32MB FPM 72-Pin SIMM

    ET6000 2.25MB PCI video card

    Sound Blaster 16 CT4170 ISA sound card

    3Com Etherlink III ISA network card

    2GB CompactFlash card with CompactFlash to IDE adapter

    MS-DOS 6.22 with Windows 3.11

The computer has been running for a few weeks now and it has worked flawlessly. It's nice have a straight up 486 build. I had a 486DX2-66 computer way back in 1992. It was the first time I ever assembled my own system. This build brings back a lot of memories.

Motherboard with original 486DX2-66 CPU
Post screen (Notice the Lazer-Tron name)
Computer running Windows 3.1








Comments

Post a Comment

Popular posts from this blog

The Little Known Epson Equity Ie - An IBM PS2 Model 30 Clone

Image
I have always had a fascination with 8086 XT class computers. Mainly because there were so few of them compared to the multitude of 8088 XT class computers out there. I own a Tandy 1000 SL with an 8MHz 8086 CPU (upgraded to an NEC V30). This is much faster than my Tandy 1000 SX with a 7.16MHz 8088 CPU (upgraded to a NEC V20). I have always wanted a 10MHz 8086 based system. These are as fast as you can officially go with an 8086. Intel only made them to run up to 10MHz. I had been keeping my eyes open for quite some time when an Epson Equity Ie came up for sale on eBay. The computer was in excellent condition and I ended up buying it. This is the only computer I know of outside of IBM’s PS2 Model 25 & 30 that have MCGA graphics onboard. This is basically a cut down version of IBM’s VGA chip. It only has 64K of ram vs 256K for the VGA. It supports the 320x200 256 color mode of the VGA as well as 640x480 2 color mode, but none of the VGA’s 16 color modes. This makes it pretty useless
Read more

Turning A $20 Craigslist Purchase Into A 500MHz Gaming Powerhouse

Image
Last year I picked up a couple of computers as part of a Craigslist purchase from a local seller. One the computers cost $20 and was described by the seller as "nothing special". It had a PC Chips M572 motherboard with an i430TX chipset, Pentium 133MHz CPU, 40MB of ram, 40GB hard drive, 1.44MB 3.5 floppy drive, DVD drive, 8MB ATI RageXL PCI video card and a low end Ensoniq PCI sound card. I was originally going  to take the motherboard out, but there was something about that motherboard that I remembered it could be upgraded with a much better CPU. I checked online and there was indeed a patched BIOS available to allow for the use of a K6-2+ or K6-III+ CPU. I download the patched BIOS and applied the BIOS update to the motherboard. The M572 motherboard has PnP CPU setup in the BIOS. There are no jumpers to set. This makes for easy changes to the motherboard. You can set the voltage from 2.0 to 3.5 volts, FSB speed of 60, 66, 75, or 83 MHz and CPU multiplier of 1.5 to 5.5. I
Read more

386/40 - Fun, Frustration, & Taking It To The Next Level

Image
  One of the computers I wanted to add to my retro computing collection was a 386. My initial plan was to find a period correct case and then just build it out from there. I made a post on the Vintage Computer Forum asking for such a case. A forum member, who is a recycler, reached out to me he may have what I was looking for. It turns out he had complete systems. I picked the one I liked which he told me that one was a 386. To my surprise when I got it was a 386/40 in nearly perfect condition. I upgraded the memory to 8MB, added a Cyrix FasMath math coprocessor,  XT-IDE CompactFlash adapter, Tseng Labs ET4000AX video card, Sound Blaster 16 sound card and 3Com 3C509B network card. I replaced the AMD 386/40 CPU with Cyrix 486DLC/40 CPU. I thought I was all set, but then problems began to set in. I could not get any protected mode games like Doom to run. They would just start up and then quit. I could not load an extended memory manager like EMM386 or QEMM386. I would get protection fa
Read more