On 2017-08-14 19:06, Milton King wrote:
Thank You. I probably asked the wrong question an I was thinking largest
single processor on a 100 bus. This old G4 will not do much past email and a
few web sites. As you know, all of the browsers are not supported. My last
hopeful was Roccat and not I cannot get it to run on Tiger. At Any rate, I
see some reasonably priced 500 to 733 single core mhz units on some websites.
Thank you for your informative response.
Milt King
You're welcome.Since it's about size (dimensions): yes, you can use any
single CPU card, provided it is the original small sized one (from
Apple, original processor). It is preferrable that the heat sink of the
original CPU will also fit the replacement processor daughter card.If
you WOULD replace a 7400or 7410 with a 7450, there WOULD BE a slim
chance that the original heat sink may not be enough, since the newer
7450-based G4 CPU generally produce more heat. BUT there are two issues
here, that PREVENT this possibility from actually happening. ONE, the
heat sink for this replacement CPU from the other PowerMac model will
not fit on your older PowerMac anyway, so you WOULD BE left with only
the chance to use the original one.TWO, and that is the real problem:
ALL 7450-based G4 dautgher cards from Apple have larger dimensions,
preventing any use of them in older Macs as the Digital Audio,
Quicksilver, Quicksilver 2002. The other way around is also true: the
larger Dual processor daugher cards of the earlier Gigabit Ethernet,
that will fit in all early models including the AGP Graphics, will not
fit in the later models that came with a redesigned motherboard for the
7450 processors.
IN ANY CASE, if you use a CPU from a later model with a different bus
speed, you need to adjust the multiplier on the CPU daughter card. E.g.
if you use a 533 MHz CPU from a "Digital Audio" with a 133 MHz bus in a
"AGP Graphics" with a 100 MHz bus, you only get 400 Mhz. That is due to
the multiplier set to 4:
100 MHz x 4 = 400 MHz
133 MHz x 4 = 533 MHz (skipping the number behind the comma, e.g.
exactly it would be 133.3 x 4 or so...)
So, using a later CPU in an earlier Mac is possible, but 1) it has to
fit and 2) the bus multiplier has to be modified for it to work.
I myself did this once: I got a 533 MHz G4 7410 from a "Digital Audio"
quite cheap on eBay for using it in my original Cube. The Cube had a 450
MHz 7400. To get the 7410 running at 500 MHz, all I had to do was to
remove one resistor from the CPU daughter card. That was easy, but it
may well be the other way around: you might have to add a resistor (or a
connection, like a wire) to get the correct multiplier. (It was my
intention to run the Cube with passive cooling, so downclocking the 533
to 500 MHz was intentional. Otherwise, 550 MHz would have been a good
option too.)
Concerning the bus multiplier modification, this should be a good
starting point for you:
https://linustechtips.com/main/topic/158931-mac-overclocking-database/
Find the correct PLL resisitors. Modify them to your system clock speed.
You may decide to overclock the CPU a little, there is normally no harm
in that -- except for heat reasons.
If you are more adventurous, you can also overclock the system bus from
100 MHz to 133 MHz, but this requires more than one tweak and may be
unstable since the motherboard hasn't been tested for this higher speed.
Instabilities (such as freezes and crashes) may occur.
http://www.xlr8yourmac.com/G4ZONE/sawtooth/SawtoothCPUdesign.html
Even if this all sounds very promising, THERE HAS TO BE A WARNING: There
is absolutely no guarantee that a 7450 series CPU works without any
modifications to the motherboard/firmware in a Mac designed for a
7400/7410! BUT normally they should: most third-party CPU upgrade cards
used a 7447/7448 or 7455/7457 CPU and worked without modification, so
why not an original Apple CPU?
So, again: All CPUs up to the single Digital Audio 533 will have the
correct dimension for any Power Mac G4. This is the original small
daughter card and fits in any Power Mac G4 (except the heatsink will be
different in later models!).
The Digital Audio 733 as well as the Quicksilver (original 2001 and
2002) use wider daughter cards, even when single-CPU. They WILL NOT fit
in any other Power Mac except the Digital Audio and the Quicksilver
series. The connection PINs are the same, but the dimensions don't fit
on the motherboard. The same is true for the MDD series: only MDD
processors (and Xserve G4) will fit into those machines!
So, actually, when going for an original single CPU from Apple, the 533
is your only option.
A Dual-500 will fit: it is a wider daughter board, but this one will
only fit into the original AGP Graphics up to and including the Gigabit
Ethernet. In a Digital Audio it will not fit, as the daughter board is
to wide on the wrong side. Like the Dual AND single CPU cards of the
Digital Audio with a 7450 processor won't fit into earlier models for
the same reason: the daughter card is too wide ON THE WRONG SIDE.
So there you go again. Your best option is to get a third party upgrade
with at least 800 MHz to 1 GHz or more, that has the dimensions of a
single processor daughter card from the early series, like original
Apple CPUs looked like up to and including the Digital Audio 533 MHz.
Since they are small in size, they will of course also work in all later
models (except maybe exclude the MDDs and the Xserve G4s).
This is how it should look like:
https://spectrhz.files.wordpress.com/2014/06/img_0976.jpg
Again: good luck!
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