Assembly on a Apple IIc+

From: Jim Keohane <>
Date: Sat Feb 8 15:22:01 2003

   There's apparently an ability for the 6502 cpu to do more than one thing,
in some cases, during a clock cycle. Whether that can be expressed as my
poor "2 cpu cycles per clock cycle" or whether it's better to refer to
"phases of a clock cycle" I'll leave to the poor folk following this
hread. - Jim

p.s. I almost put "thing" in quotes above but I don't know where the thread
would have meandered in that case. {double chuckle}

Jim Keohane, Multi-Platforms, Inc.

   "It's not whether you win or lose. It's whether you win!"
----- Original Message -----
From: "Sellam Ismail" <>
To: <>
Sent: Saturday, February 08, 2003 14:52
Subject: Re: Assembly on a Apple IIc+

> On Sat, 8 Feb 2003, Jim Keohane wrote:
> > I'm either being imprecise or various readings I have done were
> > imprecise. The reference to "one cycle" instruction may have been
> > to there being 2 cpu cycles per clock cycle. Also, there's the
> > some say the 6502 does when the last (or only) byte of an instruction is
> > acted upon simultaneous to next instruction's 1st byte (opcode) being
> > fetched
> Ok, I didn't realize that "one cycle" != 1 CPU cycle. I just know that
> I have a handy chart of how many clock cycles an instruction takes and the
> minimum number for any instruction is 2. I guess the key phrase is
> "clock cycles". Perhaps it's just semantics?
> > Of course, we're talking Apple ]['s which, if I can trust my memory,
> > steal every other clock cycle to refresh memory.
> I don't know myself.
> Sellam Ismail Vintage Computer
> --------------------------------------------------------------------------
> International Man of Intrigue and Danger
>  * Old computing resources for business and academia at *
Received on Sat Feb 08 2003 - 15:22:01 GMT

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