On Sat, May 29, 2004 at 05:46:03PM -0700, Ron Hudson wrote: Not sure how rare, but the 1802 is still in production (~$50), or you can find them for a lot less than that on ePay. What's rare is the 1861 "Pixie" video chip. I built a Popular-Electronics Elf here at Pole. I brought down the processor and many of the parts when I arrived, and ordered what I was missing while we still had daily flights. I finished the circuit about six weeks ago, but I still haven't found black paint to finish the switch panel. It runs, but I'm not ready to take pictures of it yet. If you aren't trying to make a picture-perfect replica of the one in the magazine, all you need is a hunk of perf board, a handful of sockets, some resistors and diodes, 11 toggle switches, 1 push button switch, a +5V power supply, and a few chips (1802, SRAM (1822/5101/2101 were used 28 years ago, but even a 2016 or 6116 would work), 2 x 4016, 2 x 4050, 4049, 4013, 4023), either a pair of hex displays (like the TIL311) or a slightly different circuit and 8 LEDs, and a clock. The two most popular frequencies are 1MHz and 1/2 of 3.579545 MHz. The P-E Elf started out at 1MHz and switched to 1.79MHz to accomodate the 1861 (by adding a 3.579545MHz crystal, a 74L00 used as an oscillator, and a 7474 to divide by two). The ACE designs specified 1.79MHz. Toggle-in programs expect one of the two frequencies. If you want to get fancy, you can hook interesting things up to the Q line, like a speaker or a relay. You can also latch some of the upper address bits and have more than 256 bytes of RAM, but that's a lot of toggling. There's an active Yahoo! Group about the 1802... http://groups.yahoo.com/groups/cosmacelf Folks are discussing new designs, there was a thread last year about reverse engineering a hand-held factory "palmtop" computer (the size of a *large* calculator) that some of us bought surplus for $4 each, there's even some people from the old days that are still around and still working with the 1802. I think you have to sign-on to access the pictures and download files (one of the pictures in the gallery is of my Quest Elf I built as a kid). -ethan -- Ethan Dicks, A-130-S Current South Pole Weather at 30-May-2004 02:40 Z South Pole Station PSC 468 Box 400 Temp -76.2 F (-60.2 C) Windchill -125.3 F (-87.40 C) APO AP 96598 Wind 20.8 kts Grid 358 Barometer 664.3 mb (11225. ft) Ethan.Dicks(a)amanda.spole.gov http://penguincentral.com/penguincentral.html