Way back in May 1995, Apple introduced the first of a family of
computers that put the CPU on a daughter card, making it easy for Apple
to offer a faster version simply by putting a faster CPU on a new
daughter card.
Daughter Cards
The Power Mac 9500 first shipped at 120
and 132 MHz speeds, sporting the then-powerful 604 processor. The
slowest model in the family, the Power Mac
7500, shipped in August with a 100 MHz 601 processor.
I don't recall that Apple ever sold replacement daughter cards, but
companies such as Sonnet, Newer Technology, XLR8, and others certainly
did. And when the G3 processor became available, they offered G3
upgrades. And when the G4 was available in quantity, they made G4
upgrades available.
Until recently, we were limited to a top speed of 500 MHz on
daughter card upgrades. The 50 MHz bus on the Power Macs and most
clones combined with the 9x or 10x maximum multiplier put a ceiling on
speed. Adding to the difficulty were the ongoing redesigns of the G3
and G4 CPUs, meaning you couldn't just plug a new processor into an old
card design.
Still, you could take a computer designed to run a 100 MHz 601 CPU
and drop in a 500 MHz G3 (see our Guide to G3
Daughter Cards) or a 450 MHz G4 (see our Guide to G4 Daughter Cards). That was pretty
darned impressive - but it pales in comparison to Sonnet's latest offering.
You may remember that Sonnet was the only company to offer G3 and G4
upgrades for the "unupgradeable" Power Mac
7200. This upgrade used a 33 MHz PCI slot and incorporated Sonnet's
Fortissimo technology to double bus speed, making it possible to offer
CPUs as fast as 400 MHz.
The same kind of thinking has gone into the new Crescendo/PCI G4, a
card advertised on page 8 of the August 2002 issue of Macworld and
expected to be officially unveiled at this week's Macworld Expo. If the
new PCI daughter card isn't using the same bus doubling technology as
the Crescendo/7200,
it must be something similar, because there's no other way to run a G4
at 800 MHz on a 50 MHz system bus.
Update: Since posting this article, we've been informed that the
744x and 745x G4 processors support a multiplier of 16x, which means
they don't require any cache doubling to reach 800 MHz on a 50 MHz
system bus.
Yeah, you read that right - 800 MHz. Stick that in your Power Mac
7500 and watch it smoke the Power Mac G3! With the 800 MHz
Crescendo/PCI 400, those old PCI Power Macs and clones designed for
daughter cards can offer performance in the same ballpark as Apple's
800 MHz iMac, PowerBook, and Power Mac G4.
ZIF Reaches 1 GHz
When Apple introduced the beige G3, they
moved from CPU daughter cards to an even less costly system, Zero
Insertion Force (ZIF) sockets. The old beige G3s used a 66 MHz system
bus and support G3 and G4 upgrades to 500 MHz. The newer blue & white G3s have a 100 MHz system bus and
could theoretically support 800 MHz or faster CPUs, although to date
none have been announced.
Apple made some changes to the motherboard when they announced
the "Sawtooth" version of the Power Mac
G4, the model that used an AGP slot for video, not the older,
slower PCI technology. Ranging in speeds from 350 MHz on up, the
upgrade market has been almost nonexistent (XLR8 makes a 550 MHz G4 - it's
the only one I know of) until now.
The Encore/ST G4 advertised in Macworld magazine promises 800 MHz
and 1 GHz options - twice as fast as Apple ever offered with the
"Sawtooth" design, and 1 GHz is faster than today's entry level
Power Mac. No pricing yet, but these upgrades should be very attractive
to those with fully decked out Power Mac G4 systems who need to really
boost CPU performance.
Two Brains Are Better Than One
Sonnet's Encore/ST G4
Duet upgrade (US$600) puts a pair of 500 MHz G4 CPUs into any Power
Mac G4 with AGP video, not only allowing those with slower G4
processors to reach the 500 MHz mark, but also adding dual processor
support for even more performance under OS X and some classic
applications.
XLR8 also offers a dual processor G4
upgrade, but theirs takes Apple's 450 or 500 MHz dual processor Power Mac G4 and boosts them to 550
MHz.
Conclusion
The CPU upgrade market was stuck at the 500 MHz wall for years. It's
nice to have a couple 550 MHz options available today and know that far
faster upgades will be available in the near future. Stay tuned to Low
End Mac for more information as we learn what Sonnet, XLR8, and others
announce at the Expo this week.
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We believe in the long term value of Apple hardware. You should be able to use your Apple gear as long as it helps you remain productive and meets your needs, upgrading only as necessary. We want to help maximize the life of your Apple gear.
We believe in the long term value of Apple hardware. You should be able to use your Apple gear as long as it helps you remain productive and meets your needs, upgrading only as necessary. We want to help maximize the life of your Apple gear.
We believe in the long term value of Apple hardware. You should be able to use your Apple gear as long as it helps you remain productive and meets your needs, upgrading only as necessary. We want to help maximize the life of your Apple gear.
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Page not found | Low End Mac
Welcome Image and Text
We believe in the long term value of Apple hardware. You should be able to use your Apple gear as long as it helps you remain productive and meets your needs, upgrading only as necessary. We want to help maximize the life of your Apple gear.
