Erik,

You are right and i know the rest of he world uses that technology, but even so, a freshman student, just entering his 4 year BS degree program is still taught about basic RAM, ROM and IO interfacing. And alas, the text for such beginner level does specify such obsolete ICs as teh 8255 and 8279.

Moreover, i have seen quite a number of 8051 trainer boards (i dont remember from which companies) tha have about exactly the same structure. Infact this was one of my inspirations and reasons to go with this design. The only change i made to this structure was the addition of a 8259 PIC which i know is designed to be used by the 8088 / 8086 processors. I thought if i am able to marry it with teh 8052, it would be something new, albeit stupid.

Ok, i know that whatever board(s) are used for teaching OR whatever boards i worked upon in my days didnt need double writes to the 8255, but hey, even i never wanted to do the double writes ! It just s happens that in this particular wire-wrap design, i have to do it to make the darn things work. I am sure thsi will not be necessary in teh PCB version.