Upgrading mac68k CPUs

Since I can't seem to find a reasonably priced 68060-based
system out  
there, I am looking at the CPU upgrade possibilities for 68k
Macs. I  
have been reading FAQs all over the place about upgrading
Mac CPUs. I  
have read that you can easily swap a 68LC040 out and put a
68040 in  
its place. I have not found a clear answer on one thing
though. Can I  
put a faster 68040 chip in place of a slower 68LC040 chip? I
just  
purchased an LC 575 motherboard for my Color Classic (which
now has a  
Color Classic II board in it) and I want to replace its
processor  
with a full 68040. It now has a 33 MHz 68LC040 and I want to
put in a  
40 MHz 68040. Would that work? I am thinking it will not but
I am  
hoping it will. If that would work than I assume I could
upgrade my  
Quadra 650s to 40 MHz 68040 chips as well.

Bryan

Hi,

I think the CPU will work at 33MHz. If you like to make it
work at 40MHz
you have to do the "Quadra Chipping". Info about
this you can find here:

http://lowendma
c.com/chip/quadra.html

On this page they say you can go with your Q650 as far as
44MHz with
proper cooling  (by changing the original 16,67MHz
oscillator with a 22MHz
version). Using higher CPU speeds give instabilities or
unusable serial
ports.

The LC575 will not work at 40MHz (http://hom
epage.mac.com/schrier/lc575.html)

Regards,

Johny.

P.S. IIRC am running a 33MHz 68040 instead of an 25Mhz
68LC040 version.


On Wed, 6 Sep 2006, Bryan Vyhmeister wrote:

> Since I can't seem to find a reasonably priced
68060-based system out
> there, I am looking at the CPU upgrade possibilities
for 68k Macs. I
> have been reading FAQs all over the place about
upgrading Mac CPUs. I
> have read that you can easily swap a 68LC040 out and
put a 68040 in
> its place. I have not found a clear answer on one thing
though. Can I
> put a faster 68040 chip in place of a slower 68LC040
chip? I just
> purchased an LC 575 motherboard for my Color Classic
(which now has a
> Color Classic II board in it) and I want to replace its
processor
> with a full 68040. It now has a 33 MHz 68LC040 and I
want to put in a
> 40 MHz 68040. Would that work? I am thinking it will
not but I am
> hoping it will. If that would work than I assume I
could upgrade my
> Quadra 650s to 40 MHz 68040 chips as well.
>
> Bryan
>

On Sep 6, 2006, at 2:44 AM, Gheorghe Ardelean wrote:

> I think the CPU will work at 33MHz. If you like to make
it work at  
> 40MHz
> you have to do the "Quadra Chipping". Info
about this you can find  
> here:
>
> http://lowendma
c.com/chip/quadra.html

I did come across this link. Thank you though.

> On this page they say you can go with your Q650 as far
as 44MHz with
> proper cooling  (by changing the original 16,67MHz
oscillator with  
> a 22MHz
> version). Using higher CPU speeds give instabilities or
unusable  
> serial
> ports.

It sounds interesting but I'm not sure it is worth the
instability.

> The LC575 will not work at 40MHz (http://homepage.mac.
com/schrier/ 
> lc575.html)

OK. Thank you for that link. It is very helpful.

> Regards,
>
> Johny.
>
> P.S. IIRC am running a 33MHz 68040 instead of an 25Mhz
68LC040  
> version.

You are saying that you are running a faster chip than was
intended?  
What machine are you doing this in?

Bryan

> Since I can't seem to find a reasonably priced
68060-based system out there,

You do know that m68060 upgrades don't exist for Macs (I'm
assuming you 
do...)

> I am looking at the CPU upgrade possibilities for 68k
Macs. I have been 
> reading FAQs all over the place about upgrading Mac
CPUs. I have read that 
> you can easily swap a 68LC040 out and put a 68040 in
its place. I have not 
> found a clear answer on one thing though. Can I put a
faster 68040 chip in 
> place of a slower 68LC040 chip? I just purchased an LC
575 motherboard for my 
> Color Classic (which now has a Color Classic II board
in it) and I want to 
> replace its processor with a full 68040. It now has a
33 MHz 68LC040 and I 
> want to put in a 40 MHz 68040. Would that work? I am
thinking it will not but 
> I am hoping it will. If that would work than I assume I
could upgrade my 
> Quadra 650s to 40 MHz 68040 chips as well.

m68040 processors are often overclockable to 40 MHz. I've
OC'd many, and 
I've never seen one that didn't work fine at 40 MHz.

You can swap out an LC m68040 for a full '040 in any system
(although it'd 
be very hard to do that with a surface mount '040 in a
PowerBook). The 
ROMs will be fine with the full '040.

As far as speed is concerned, yes, you can put in a faster
chip, but the 
speed rating isn't really a big concern. It won't run any
faster unless 
you make changes to the motherboard.

The 575s can be safely taken to 33 MHz:
http://hom
epage.mac.com/schrier/lc575.html

Quadra 650s and Quadra 800s can be taken to 40 MHz very
easily by using 20 
MHz oscillators (less than $5 USD from many places online).
Quadra 605s / 
LC475s can be taken to 33 MHz, like the LC575, by just
moving surface 
mount resistors. They can also be taken to 40 MHz by using
20 MHz 
oscillators, but that's a little more work.

John Klos
-- 
Today is the day that my destiny calls me!
   Meowth

On Sep 6, 2006, at 2:03 PM, John Klos wrote:

>> Since I can't seem to find a reasonably priced
68060-based system  
>> out there,
>
> You do know that m68060 upgrades don't exist for Macs
(I'm assuming  
> you do...)

Yes, I am aware of that. I was looking at Amiga machines and
also  
mvme68k machines (which I would love to use but I don't
know enough  
about them to know what to get).

>> I am looking at the CPU upgrade possibilities for
68k Macs. I have  
>> been reading FAQs all over the place about
upgrading Mac CPUs. I  
>> have read that you can easily swap a 68LC040 out
and put a 68040  
>> in its place. I have not found a clear answer on
one thing though.  
>> Can I put a faster 68040 chip in place of a slower
68LC040 chip? I  
>> just purchased an LC 575 motherboard for my Color
Classic (which  
>> now has a Color Classic II board in it) and I want
to replace its  
>> processor with a full 68040. It now has a 33 MHz
68LC040 and I  
>> want to put in a 40 MHz 68040. Would that work? I
am thinking it  
>> will not but I am hoping it will. If that would
work than I assume  
>> I could upgrade my Quadra 650s to 40 MHz 68040
chips as well.
>
> m68040 processors are often overclockable to 40 MHz.
I've OC'd  
> many, and I've never seen one that didn't work fine
at 40 MHz.
>
> You can swap out an LC m68040 for a full '040 in any
system  
> (although it'd be very hard to do that with a surface
mount '040 in  
> a PowerBook). The ROMs will be fine with the full
'040.
>
> As far as speed is concerned, yes, you can put in a
faster chip,  
> but the speed rating isn't really a big concern. It
won't run any  
> faster unless you make changes to the motherboard.

I understand.

> The 575s can be safely taken to 33 MHz:
> http://hom
epage.mac.com/schrier/lc575.html
>
> Quadra 650s and Quadra 800s can be taken to 40 MHz very
easily by  
> using 20 MHz oscillators (less than $5 USD from many
places  
> online). Quadra 605s / LC475s can be taken to 33 MHz,
like the  
> LC575, by just moving surface mount resistors. They can
also be  
> taken to 40 MHz by using 20 MHz oscillators, but
that's a little  
> more work.

Thank you for the info.

Bryan

On Sep 6,  1:36am, Bryan Vyhmeister wrote:
>with a full 68040. It now has a 33 MHz 68LC040 and I
want to put in a  
>40 MHz 68040. Would that work? I am thinking it will not
but I am  
>hoping it will. If that would work than I assume I could
upgrade my  
>Quadra 650s to 40 MHz 68040 chips as well.

You can generally replace a CPU with a faster one, so long
as the
replacement CPU's speed is equivalent to or faster than the
system
clock speed.  Replacing a 33MHz CPU with a 40MHz part will
work OK
(though the system will still be running at 33MHz unless you
change
out the oscillator too).

~Steve

Bryan Vyhmeister wrote:
> Since I can't seem to find a reasonably priced
68060-based system out 
> there, I am looking at the CPU upgrade possibilities
for 68k Macs. I 
> have been reading FAQs all over the place about
upgrading Mac CPUs. I 
> have read that you can easily swap a 68LC040 out and
put a 68040 in its 
> place. I have not found a clear answer on one thing
though. Can I put a 
> faster 68040 chip in place of a slower 68LC040 chip? I
just purchased an 
> LC 575 motherboard for my Color Classic (which now has
a Color Classic 
> II board in it) and I want to replace its processor
with a full 68040. 
> It now has a 33 MHz 68LC040 and I want to put in a 40
MHz 68040. Would 
> that work? I am thinking it will not but I am hoping it
will. If that 
> would work than I assume I could upgrade my Quadra 650s
to 40 MHz 68040 
> chips as well.

That's exactly what I did.  I cobbled one working Q840 out
of two, and 
used the spare processor for my Mystic.  Works great.  It
still only 
_runs_ at 33MHz (that's dictated by the oscillator, not the
chip) but 
there's no real voodoo involved.

The real trick is using a slower-rated chip at faster speeds
- 
overclocking.  It doesn't always work.  The chip has been
proven at its 
rated speed.  It might actually be capable of higher, but
you never know.

Tim

-- 
Tim & Alethea
christtrek.org