Apple II Plus 6502 vs. 6502a?

The 6502 is a 1MHz design, and the 6502A is designed for 2MHz, is also more prevalent.

.. and with that, the unique characteristics of the II design come into play.

As a programmer, if you are so anally relying on timing to accomplish stuff and your code does not run on something, it's probably because there's a 6502, not A, in there. Or the other way around.

Mostek produced the 6502A, and it was intended to be 100% compatible with the MOS 6502, though it's designed around a 2MHz clock. Think Apple ///.

From there on out, further 6502x derivatives were built on that.

I believe it's possible to put in 6502A in ][ or ][+ only some software that relies on specific timing would fail. There were accelerators for the pre-//e line that could go ~4MHz but had a fallback key on boot up to run at 1MHz to keep it compatible.

Maybe the card is compatible with ]['s with accelerator chips as well hence the > 2MHz mention.

Yes, putting a 6502A in the oldest II's isn't an issue. There are -far more- 6502A's out there, and any compatibility is going to be built on the highest percentage of the marketshare.

But the Uthernet specs are written because it's been established that it -does not- function without the 6502A.

tevion5 said:

Ahh so a run of the mill II plus will not have the "a"?

Click to expand...

It's possible, I've seen them both ways. "Check first" and get one at the same time, if needed..