Re: WDC W65C816S8PL-14 MHZ

[toddpw@avarice.ugcs.caltech.edu (Todd P. Whitesel)]

thoang@rigel.oac.uci.edu (Trangdaithi Hoang) writes:

>The good news is that at 5 V it not only runs reliably at 14 MHz, but
>also up to 15.5 MHz.  I haven't tried it at > 5 V other than at 20
>MHz.  I don't plan to play around with increasing the voltage unless
>I have free time and nothing fun to do.

This _is_ good news. (Can't wait for mine to show up..)

While I have the floor, a word of caution to the voltage experimenters.

The 65816 outputs signals to the rest of the board, and these signals must
not exceed the safety limits of the other chips. Most TTL and CMOS will
let you feed them up to .5v over _their_ Vcc pin (i.e. 5.5v in the IIgs).
After that point they will protect themselves by shorting their inputs to
+5v with a strong diode (this is how static shock protection works) and
that will draw as much current from the 65816 as it can manage, which
will turn the 65816 into a mini popcorn popper real fast.

The 65816's outputs are (I believe) guaranteed to be at least Vcc-.5 or
something like that (check the data sheet), so you are really playing with
fire if you jack your 65816 over 6 volts. If anyone has done that and not
burnt out their CPU after leaving it running for a week or so, I'll be
really surprised.

Todd Whitesel
toddpw @ ugcs.caltech.edu