Re: 65c02 in ][+ problem

["Server" <Server@aol.com>]

I've got a II+ that I ran a 4Mhz 65802 on in the motherboard socket, with no
problems.  I later put the 65802 in a Transwarp IIe, and ran it in the II+
with no problems.  I believe that I read a long, long time ago that the
65C02 was not a good replacement cpu for the II+ because of some instruction
timing problems with the 65C02.  I know that the 65802 was a preferred
replacement though.  Sorry I can't be more helpful, but it was a long time
ago.


"David Empson" <dempson@actrix.gen.nz> wrote in message
1f3w42i.1w039qopbbmucN%dempson@actrix.gen.nz">news:1f3w42i.1w039qopbbmucN%dempson@actrix.gen.nz...
> John L <jd@logotech.8m.com> wrote:
>
> > I've got a Rockwell 65c02 CPU running quite well in my ][+ (64K with
> > language card), however, I can't seem to get ProDOS 2.0.3 running at
> > all.  When I attempt to boot P8 2.0.3 from any device I get the splash
> > screen then the system locks up with a few garbage characters.
>
> One possible explanation is that ProDOS is trying to use a CPU detection
> algorithm which involves 65802/65816 instructions but doesn't allow for
> the Rockwell R65C02.
>
> The R65C02 defines unique instructions for all opcodes with low order
> four bits of '3', '7', 'B' or 'F'.  These intructions are reserved on
> standard 65C02 (they are guaranteed to be NOP), and have completely
> different functions on the 65802/65816.
>
> (On the original 6502, all undefined opcodes are reserved and have
> behaviour which is not documented officially, which is typically a
> mixture of other related instructions.)
>
> Has anyone else had P8 2.x running successfully on a II+ with replaced
> CPU?  If so, what CPU was involved?
>
> I suspect that P8 2.x will work fine in a II+ if a 65802 or Zip chip is
> used.  Most (all?) non-Rockwell 65C02s don't work at all in a II+, due
> to timing or electrical signal problems.
>
> > I thought perhaps the lockup was due to P8 2.0.3 requiring the //e
> > mousetext ROMs - further investigating reveals this not to be (A 65c02
> > CPU is the only requirement).
>
> There is no possibility that any software would fail to operate based on
> the character set available in the video ROMs - these ROMs are not
> accessible to software, and only affect the appearance of data on the
> screen.  The lack (or availability) of MouseText could cause a program
> to be difficult or impossible to use due to the screen display showing
> the wrong character set.
>
> The IIe firmware might have been a requirement, but I don't think that
> is the case with P8 2.x.