The performance is the main issue today, I believe. These devices had a nominal access time of about 450ns, which would ostensibly work (as it was designed to do) with the "standard" i805x, but not necessarily with the faster versions.

The voltage requirements are about the same, BUT, the output current both sinking and sourcing, of the 8155 is quite small, on the order of 2 mA sinking and perhaps 1.2 mA sourcing (I'm guessing here, as it's been almost 30 years.

I used these guys once or twice, but, due to their dismal output current, requiring external buffering with TTL, I gave them up almost right away, replacing the buffers with output latches and providing input paths with tristate buffers.

If one needs the 256 bytes of RAM and the timer and the I/O, then yes, it could work out, but it's more economical simply to buy an MCU that has all the I/O pins already built in, even if it's not an 805x. Today's technology is also limited in usefulness, as one has to provide level shifters just to use a common mostfet with today's low-voltage parts.

RE