Catching up with the P8284A (quickie)

I have a few secret projects I’ve been working on, but a quick thing that I can show is how to make a working clock with a P8284A (Here is the datasheet)

This chip was used for generating the clock for 8086s and 8088s, so it’s kind of a big deal. The unfortunate thing is, they are hard to find nowadays.

If you are able to get your hands on one and want a quick and dirty way to set up one, then use the layout below:

or use this pdf.

Now wait! I hear you exclaim! You’re using a 24MHz to drive an 8088!? Those things can only handle a max of 8MHz and you’re supplying a crystal 3x as much!

Yes, this is true, but the P8284 outputs a signal 1/3 that speed. It’s wave output is a little weird too. Take a look:

Now I did make a board layout for it as shown below. The first image is of the front:

And here is the back:

I haven’t tested it, but I’m gathering a batch of boards to ship off to JLCPCB for further testing.

The giant circle in the middle is a mounting hole which should fit a m3 screw, but it might be too tight, we’ll see.

I won’t go in to too much detail about the various values I chose, but there are some “optional” parts (i.e. the capacitors). I don’t recommend skipping the timing (electrolyte) and bypass (ceramic) cap. You can get some more information on that here and other videos:

So maybe if you’re fixing your old IBM AT or IBM PS/2, then this might help 🙂

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