Re: Apple //c++ experiments...

[John <zzzjoki@yahoo.com>]

On Aug 15, 1:55 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
> John wrote:
> > On Aug 11, 4:37 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
>
> >>I recently acquired a //c+ (Yay!), so I decided to try replacing the
> >>16MHz accelerator oscilator with a 32MHz oscillator to bump the speed
> >>from 4MHz to 8MHz (making it a "//c++"  ;-).
>
> >>I was concerned that simply replacing the oscillator might shorten
> >>the "slowdown" times for slow slots and the speaker and joystick,
> >>which could pose a problem.
>
> >>The answer is that the slowdown times are timed by counting down
> >>the 1MHz Apple bus clock, not the accelerator clock, so they are
> >>unaffected by oscillator frequency--a very convenient result.
>
> >>Also, the Zip Chip Utilities, and in particular the ZIP.SYSTEM program
> >>that runs before any other system program on the boot volume, configures
> >>the IIc+ just as it would for any slotted Apple II.  Of course, it is
> >>necessary to leave slots 5 and 6 slow for disk access to work, and in
> >>the IIc+ it does not appear to be possible to set the joystick to
> >>"fast" (but the speaker can be set to fast).
>
> >>In short, just replacing the 16MHz oscillator with a 32MHz oscillator
> >>converts a IIc+ into a "IIc++", and the Zip utilities can be used to
> >>configure the actual speed, or even to default the accelerator to "off".
>
> >>BTW, I understand that some IIc+ machines will not run with a 32MHz
> >>oscillator.  I have several 32MHz oscillators, and found that one type
> >>would not work, while another (RXD 1100) did, so maybe the problem
> >>some have reported is an oscillator problem, not a IIc+ problem...
>
> >>I tried a 39.750MHz oscillator, and it didn't work--but it was of the
> >>same type that did not work at 32MHz, so I don't think that proves
> >>anything.  I was hoping it would work, so that I could run at 32MHz
> >>with some assurance of some "headroom" for reliability...
>
> >>-michael
>
> >>NadaNet file server for Apple II computers!
> >>Home page:  http://members.aol.com/MJMahon/
>
> >>"The wastebasket is our most important design
> >>tool--and it's seriously underused."
>
> > I haven't opened the //c+ up so, what kind of oscillator is it?
> > I have a mystery 27 MHz crystal for a radio or something. Maybe I
> > should just try it and see.
>
> The accelerator clock oscillator is under the middle of the
> keyboard.  It is a 14-pin DIP form-factor oscillator, but like
> all such oscillators, it has only the four "corner" pins (1, 7,
> 8, 14).
>
> A plain (2-lead) crystal won't do--you need an oscillator (which
> has a crystal inside the sealed metal case).
>
> The 32MHz replacement oscillator will look almost exactly like
> the installed 16MHz oscillator, except for markings.
>
> -michael
>
> NadaNet file server for Apple II computers!
> Home page:  http://members.aol.com/MJMahon/
>
> "The wastebasket is our most important design
> tool--and it's seriously underused."

If and when I decide to do this I'll try and match it except for the
speed.
Thanks, again, for the help. May your //C+++ sing a higher note
clearly.