Re: Apple IIe Enhancement Kit

["Michael J. Mahon" <mjmahon@aol.com>]

aiiadict@gmail.com wrote:
> INA and DEA seem like nice ones to me (never tried using
> 65c02 instructions)...  I would type them into an assembly
> assuming they were legal codes (or, falsely remembering
> them as legal).  instead, tay, iny, tya and it seems a bit
> far to go just to increment A.

Of course, if you know the state of the Carry flag, and
don't need to preserve it (both common situations), then
ADC #1 or ADC #0 and SBC #1 or SBC #1 do the job easily...

If you don't know the state of C, then adding a CLC or SEC
gets you there.

Don't get me wrong--there are good places to use the new
opcodes.  It's just that it is seldom hard to avoid using
them.

Of course, in an interpretive loop, every cycle counts,
so the added cost to have two versions (65C02 and 6502)
is worth it.

-michael

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Home page:  http://members.aol.com/MJMahon/