test strategies

Yeah!

Double Eurocard, 80186 , dual ported DRAM to Multibus I, floppy wd2793, SCSI, Zilog Z8500 serial ports, TI9914 IEEE-488 and parallel I/Os:

bottom side:

detail GND/VCC distribution:

Gerhard

Nice good old color code resistors..

My designs were "CPUs" -- lots of MSI used to build the various parts of the processor (ALU, register file, microstore, etc.). More conventional chips (memory, I/O devices) would reside on other boards.

I had a fair bit of experience on projects that used machine-wrapped Augat panels (18x72" assemblies with 1/2" dia Cu bus bars down the length -- no belt buckles, jewelry, wire-framed eyeglasses, etc. allowed!) and really liked how clean the layout ended up (at least on the *top* side :> )

I laid out a 12x12 (!) card with dual edge connectors instead of relying on perf board. This let me utilize off-the-shelf "card cages" to mechanically support the cards while giving me freedom to use the card edge connectors as I saw fit (no need to interface to off-the-shelf cards using someone else's notion of an interconnect bus!).

The top and bottom were large pours to act as power and ground planes. This was a real win on the Augat panels that I wanted to leverage. Everything was bipolar (e.g., schottky logic, ROMs) so there was a fair bit of power consumed. The rest of the board was rows of 0.1"-spaced holes on 0.3" centers in a pattern like:

o o o o o o o o o o

The hole in each ALTERNATING doublet was *not* isolated from the ground/power plane so installing a single WW pin in the hole and tacking it in place on the top (or bottom) side, as appropriate, connected it to power or ground. Thus giving you a nearby point to wrap to power/ground AND a place to install a bypass cap, topside. Soldering, of course, done before laying on wires!

On 0.3" centers, regular DIPs would straddle a pair of rows with wider DIPs (e.g., 0.6" 24 pin) straddling two rows. While you couldn't place devices side by side (like you could on Augat panels), the enforced separation served as a good wiring channel. And, made the power/ground pins accessible topside for bypass caps.

I made a point of picking a drill size for the holes that matched the outer diameter of the pins used on Augat WW sockets so you could press-fit a socket into the holes and secure it to the board without having to add a wrap on the backside to hold it in place (as was necessary for regular perf board). So, I could effectively make an Augat panel without the expense ($$$$$).

As pins only existed where they were needed (i.e., undersides of sockets), you could keep your bearings as to the topside layout from below (the Augat panels were just rows of pins so you couldn't easily tell where a device began/ended among them).

To connect to the card edge fingers, I put a pair (top+bottom foil) of rows of holes with surrounding lands so individual pins could be tacked in place for each conductor.

As the card was ample size, I didn't have to resort to daughter cards or interboard wiring "within" a design. (I didn't use "integrated" devices like the 29xx bitslice series so there was a *lot* of logic on the board predating PALs/PLAs, etc.)

I found them so handy that I reproduced the layout on other jobs. It was particularly amusing to see some "giant" board rendered into a ~40 pin "custom" a fraction of the size and power! Getting off a chip via a pin/pad driver uses a disproportionate amount of power vs interconnects *within* a chip! (my designs are always fully synchronous so everything is switching at the same time)

But, you're still left with a lot of labor to make a second copy of a prototype. And, you have to treat them with care lest you late discover that two pins have accidentally made intermittent contact.

This was much more fun than the more highly integrated designs that are now so common -- far less design choice! :<

Nowadays one can use free layout tools to order a bunch of 4-layer boards from JLC and others and get a few boards in a couple of weeks for beer money.

Few parts come in DIP packages any more.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Though, to be fair, things are so much faster now that one can "emulate" a 40MHz custom CPU just by writing some code (if you ignore cycle-accurate criteria).

OTOH, one could *implement* a 40MHz CPU on a 4-6 layer board whereas the current crop of processors all rely on HDI and closer to 10 layers!

Amusing to think we designed custom CPUs because bog-standard CPUs were too slow to meet the needs of the applications. Now, using bog-standard CPUs to implement the features of those custom CPUs!

Would that we could have the custom ability AND the modern levels of performance!

Soldering veroboard the same day Want 2? One more day. bit of 60/40 (yes I know you use 38? is all it takes. Faster cheaper more fun. End easy modifications / corrections / adding new features. May even be more reliable.

Many .1 inch adaptors on ebay, using those all the time. Some come with the chips already on it.

Jan Panteltje snipped-for-privacy@comet.invalid schreef: |---------------------------------------------------| |"[. . .] | | | |It is bad thing they dropped Ceefax. | |Almost all German and Dutch channels still have it,| |with lots of program data and ads." | |---------------------------------------------------|

I showed a German Teletext in the British Isles. He contrasted it with German Teletext, because he said that German Teletext is bare. (S.

I think you mention German twice, what did he contrast (compare? it with?

You can make teletex as nice as you want I have done some coding to display it on my old PC in Xwindows

These days you just type:

Some of that code I wrote I still use (see above).

Jan Panteltje snipped-for-privacy@comet.invalid schreef: |----------------------------------------------------------------------------| |"I think you mention German twice, what did he contrast (compare? it with?"| |----------------------------------------------------------------------------|

This German did not contrast technologies. He contrasted contents of German teletext with non-German teletext: i.e. basic data versus interesting essays written like magazines.

|----------------------------------------------------------------------------| |"Some of that code I wrote I still use (see above)." | |----------------------------------------------------------------------------|

Congratulations! (S.

OK, got it.

What is also fun, you can use a Philips SAA5281 teletext chip to add subtitles to analog video.

Here I use it to add flight information to my drone Head Up Display: