Why would you even consider EMC on a prototype of which you're building exactly one unit, particularly if you're planning to build a PCB later, provided the product turns out to be useful, which it probably won't, in this case?

Yes, there are parts that are fast, but, with the capacitances he's hooking to his bus, if he's doing this correctly, the edge rates will be limited. Secondly, while the last 62256-types I used were 8 ns parts, I doubt he's using those, since they don't come in packages suitable for wire-wrap.

There's no doubt that a multilayer PCB, designed with EMC considerations at the forefront, can produce a quiteter, lower-radiation circuit but at what cost? He's wanting to build ONE unit. While the cost of the PCB ought to be about $10US at q100, the first one will cost ~$8000US at $0.50 per hour if he has free software with which to create the multilayer PCB layout, and that's only if he already has the 10 years' experience at creating the layout with the tool he's using. Whereas a 4" x 6" two-layer PCB might cost $0.65 US or thereabouts in his part of the world, a multilayer board will cost considerably more.

IF he builds this thing with wire-wrap, when he's done, he'll still have the wire-wrap board, the sockets, the components, and the experience he's gained from working up this completely silly design. He'll be smarter next time, and he won't have to give up a year's income in order to gain all this knowledge.

If he's the rank beginner that he says he is, he needs, first of all, to learn how silly it is to sacrifice two ports on his MCU in order to gain the three ports on the 8255. He then needs to learn a few things about the general notion of what an 8-bit MCU can appropriately be used for and lastly how silly it is to use a mid-range MCU like he's wanting to use together with a three-generations-obsolete part like his 8255. Now, there are applications that the 8255 can handle, but there are better ways, particularly if he doesn't intend to attach the 8255 as a memory-mapped peripheral, which, of course, he can't do if he pushes up the speed of his MCU beyond the typically half-microsecond access time of his 8255. He also needs to learn that the PIC (interrupt controlle) doesnt' marry up with the 805x types nearly so well as with the 8080 for which it was designed.

I doubt he has to meet CE standards, and I doubt he can afford to invest what he would have to invest in order to produce a multilayer board that meets them. I also doubt that anyone will want to buy such a board, since the peripherals he's proposing are so out-of-date. AFAIK, there's only one manufacturer still offering the 8255 and I don't know about the 8259.

The 8279 is not at all designed for use with the 805x, particularly since he's not going to use the keyboard or the display for which that part was intended. He's got the intention of putting on an LCD. They didn't even have those when the 82xx series was designed.

Let him build his one-of-a-kind project, and let him learn what he can learn from it. Eventually he'll arrive at the conclusion that there are reasons why these parts are scarce and no longer made. When he gets to the point at which he realizes that he needs to use parts intended to be used together, and that they should be parts of the same generation in order to allow seamless integration, he'll have learned something. In the meantime, there's no need for him to epxend resources sufficient to feed a family of four for a year just to meet EMC standards that don't have to be met.

You're a smart guy, Kai, and expert in your field, but I think you're solving the wrong problem here.

RE