The Quarky Engineer

A slight diversion this evening…..the powerhouse that is the PCJr.

The PCJr was an eventual failure in the market, with around 400,000 total produced. Interestingly enough Tandy even made a PCJr semi-clone called the Tandy 1000.

The power supply was bad, but I had a spare so I was able to get that working. At first the keyboard wasn’t working, which is a somewhat common problem with these PCJrs. There is a capacitor in the keyboard that eventually starts shorting, so a replacement fixed that.

I have a cartridge that goes in the cartridge port that maps an SD card as a hard drive, which makes it much easier to move things around.

Once I get it formatted, I’ll get Kings Quest running.

On to a 486. The ever classic 486DX2-66. The DX2-66 was perhaps the most popular of the 486 line, and was the standard platform for many games in the early 90s. The 486 was the first x86 processor with more than 1 million transistors ( close to the first processor ever, with that distinction going to the Intel i860 that same year).

It was produced on a 1000nm process at the start, moving to an 800nm process along the way. 5000 dhrystones seemed like a lot back then, and it was often converted to VAX equivalent MIPS by dividing by 1757. A raspberry Pi is something in the range of 5,000,000 – 6,000,000 dhrystones for comparison.

8MBs of RAM and a VGA adapter would have been pretty good fare back in the day. I have a nice AWE32 sitting on the shelf that would fit right in as well.

When I moved to Oregon to work at Intel right after graduating college, I brought a 486DX2 with me. It was as a sweet machine.

No doubt many of my friends will have had a 486DX2 at some point.

Moving forward in time a few years – I also had an old 386SX motherboard that would not turn on. Sure enough one of the traces was damaged by the battery leaking. It seems like 70-80% of the 386 era motherboards have now failed because of this exact problem. So many of them used a Varta NiCd battery that eventually leaks, and the leak almost always eats traces.

Fortunately there was only one trace that was damaged bad enough to need a patch. I soldered in a patch and the board POSTs. A quick bath in the ultrasonic to clean up some corrosion as well. 8MBs of RAM in this one, so it would have been a nice machine back in 1989. I had a 386SX machine during part of college, so good memories with this.

I’ll have to look around and see if I have a 387SX in my parts bins.

This has been an interesting resto-project. While there are a good number of IBM PCs, IBM XTs, and IBM ATs still floating around, you don’t see very many IBM XT/286s. It was a computer IBM released after the first IBM AT came out, and it was an XT sized case with a 80286 motherboard similar to the IBM AT 5170 but sized to fit. It has a 6Mhz 80286 like the first AT, but is ever so slightly faster due to 0 wait-state memory.

The one I have is pretty amazing condition and with a very original configuration. It has the original factory installed 20MB hard drive (ST506) as well as the 1.2MB 5 1/4 floppy drive.

There is only one BIOS revision from IBM for this platform, and it does not with with the XT-IDE-CF ISA card (which gives you a compact-flash based hard drive). I pulled the EPROMs for the BIOS out and repalced the BIOS with a period correct AMI 286 BIOS, and that allowed the XT-IDE-CF to work correctly.

It has 640k, which we all know is more than anyone will ever need. 😉

I have the CGA output going into an RGB2HDMI converter that drives a display, so you get those awesome 4 color graphics!

The memory and the machine test out fine, which is pretty cool given it was first sold in 1986, 36 years ago. It was $2500 back then, which would be about $6400 now. Premium!

My rack-o-risc assembled. A little PA-RISC, SPARC, PowerPC, Alpha, and MIPS. Of course the raspberry pi serial console is probably more total computation power than everything here , but remember RISC architecture is going to change everything!

A few upgrades for my SE/30.

Time for some hi-speed networking!

While I was out on my camping trip I did a little astrophotography. Mostly with just my Sony Alpha A7IV camera and a zoom lens, but one shot with the Alpha on my Celestron C8. The Sony worked well once I got the config figured out. Next time out I’ll do a lot more exposures, but this was a good test before the clouds rolled in. Most of these were only 10-20 stacked 20-30s sets, but I did do darks, flats, and bias. A few comments on each picture.

It was fun to have a little time under the great skies of the eastern Oregon forest.. so little light pollution.. and you can almost read something with just the glow of the milky way.

I finally had a chance to do some remote camping with my setup. I did three days in the Ochoco National Forest at a somewhat remote location. I didn’t see a single person or hear any signs of life with the exception of the wildlife, so it was a nice get-away.

I was able to do a bit of astrophotography under the very dark night sky, and I was able to test all of my power management systems.

I had my Starlink with me, as there is no cell coverage of any kind here. I powered the Starlink with my Ecoflow battery pack (3.6kWh) plus a solar panel, and the panel was able to generate enough power to provide 24 hours of Starlink usage.

I also had a generator, which was nice to use during the 100+ degree peak temps to run the AC.

Everything else in the boondocking setup worked great. Plenty of water, great cooking, sleeping, etc. It is a good setup for doing remote work with no support services needed.

Summer time = more power!

Getting back to 120kWh producing days.