Just started on a SBC6120 RBC Edition kit. It’s a DEC PDP-8-compatible single board computer that uses a CMOS chipset from the early 1980s. Yes, it will be very slow, even with the optional speedy 8 MHz oscillator installed. With a 12-bit processor and 32 kilo-words of RAM, this is definitely going to be a Slow Computing device.
Lots and lots of sockets. So many sockets. It’s quite soothing soldering them all in, one hole at a time. It looks like it’ll go more quickly than the Zeta did.
> Does anyone know what each of the pins on the 6502 CPU chip in the Apple II Plus does? They all plug into the socket on the motherboard to keep the chip from drifting away. – c.s.a2 FAQ of yore
You have no idea how good it was to see that message come through over the serial link. The Zeta worked first time!
Here’s the board, fully populated:
I still have to put it in a proper case. A visit to Above All Electronics did result in getting a floppy drive (and most importantly, 3½” 1.44 MB floppies …) and all the cables, so I’ll add that later. But for now, I’ll try to remember how CP/M works …
Please excuse horrible blurry photo, but I think all the soldering is done —
This adds the crystal sockets, the 32.768 kHz RTC crystal, the status LED(s) and the reset button.
A whole new board I soldered up is the Mini-PPISD. It adds (slow) SD card storage to an SBC board:
Man, but those surface mount SD card pads are a pain. I had to get flux on the PCB pad and the bottom of the SD connector, load a little blob of solder on the iron, then warm up the pad and roll the solder into place. It made a satisfying little Zsht! noise as the flux burnt off, and the molten solder got drawn under the pad by capillary action.
Next up is checking the power and ground continuity, adding the chips, building a null modem (grr; I hate RS232, really) and finding a case. I may already have one, but I may forage at Above All to get a 3½” floppy drive and enclosure. I definitely have an old Turbo/reset button from an XT that would make a great reset breakout.
Just waiting for the full-can oscillator sockets (and most of the chips) to arrive from Mouser. I could have used 14-pin DIP machine pin sockets, as Sergey was thoughtful and had all of the holes drilled.
Most of the big sockets need to be fully soldered, as at the moment they’re just tack-soldered at the corners. Maybe I’ll put on some dronecore and have a meditative time with the Sn-Ag tonight. I’ll be glad to get the flux off the board, though: it’s not my usual stuff (which is Kester #951; no clean ftw), and what I’m using is smoky and a bit gummy. It does make nice bright joints, though, which is never 951’s strong point.
That’s all but one of the capacitors in. The big chip sockets are soothing to solder.
Apart from the bits I got in a frantic dash between Supremetronics and Creatron on College, the rest is coming from Mouser. Taking the advice of someone who should know better, I’ve ordered a made-in-DDR UA857D MME chip, since Z80 CTCs are back ordered. Sometimes, it’s good to have chips older than your colleagues …
Fun discovery #1: not all CR-2032 battery holders are the same size. This board call for the one just a tiny bit larger than the coin cell itself. Most of the ones with the retainer clip that goes over the battery are too big, and will prevent other components being installed.