Low End Mac Reader Specials

TypeStyler For Mac OS X is Now Shipping! Download The Free Fully Functional 60 Day Tryout at www.typestyler.com

OWC: Get the Right Memory / Ram for your Mac. Top Quality, Competitive Prices, Lifetime Warranty. Expert Support and Video Installation Guidies too! 4.0GB Matched Sets from $87.99, Options up to 32GB. Click here

Poker Mac Don't install Parallels to play poker online! Poker Mac will show you how to download and install a native Mac poker application such as Full Tilt Poker Mac.

Laptop Hardware Provided by TechRestore - Overnight Mac & iPod Repairs.

Compare products like desktop computers, apple laptops, apple macs, and LCD Monitors side by side! All the information and reviews to make the best purchasing decision for new mobile phones, sat nav systems, or MP3 players. The Ciao online shopping community makes searching products easy for you.

Low End Mac's Online Tech Journal

The PowerPC G3 Story: From 233 MHz to 1.1 GHz

Dan Knight - 2007.05.24

The PowerPC G3 CPU was a big step forward in design. Where the earlier PowerPC 601, 603, and 604 RISC processors had been designed for compatibility with IBM's POWER architecture, the third generation (hence G3) processor was optimized for the code being run on PowerPC computers.

A 233 MHz G3 was so efficient that it could hold its own against a 300-350 MHz PPC 604e CPU, so Apple quickly moved away from the older CPU except in multiprocessor models (the G3 has very limited dual processor support).

The G3 is officially known as the PowerPC 750 family. This article provides an overview of that processor family as used in Apple computers.

PowerPC 750

The first generation G3, the PowerPC 750, was the first PowerPC CPU designed to run on a 66 MHz bus. It found its way into the original Power Mac G3, released in November 1997. The "beige" G3 was initially offered in 233, 266, and 300 MHz versions. (It was also the first Power Mac to use an IDE bus for hard drives.)

The PPC 750 had two 32 KB level 1 (L1) caches, one for instructions, the other for data. An external level 2 (L2) cache of 256 KB, 512 KB, or 1 MB was supported running at an intermediate speed between the 66 MHz system bus and the CPU's core frequency. The PPC 750 reached speeds as high as 366 MHz, and the faster chips made their way into a later, relatively rare 333 MHz and 366 MHz revision of the beige G3.

The beige Power Macs and original iMac had a 512 KB L2 cache running at half the speed of the CPU. The first PowerBook G3 (essentially a PowerBook 3400 with a G3 transplant) ran at 250 MHz, had a 50 MHz system bus, and a 512 KB L2 cache running at 100 MHz (a 5:2 ratio).

PowerPC 755

Motorola moved to aluminum fabrication and a tighter .22 µm die to produce the PPC 755 in 1998. The new CPU supported a 100 MHz system bus and achieved speeds as high as 600 MHz. The 755 was used in early iBooks.

After this, Motorola essentially abandoned the G3 in favor of the G4 (PowerPC 7400) architecture.

PowerPC 750CX

IBM kept developing the G3, and the PPC 750CX was the first G3 CPU to incorporate an on-chip L2 cache. This eliminated the need to have a separate cache running at a fraction of the CPU's full speed. Although the onboard cache was only 256 KB in size, the fact that it ran at full CPU speed made the 750CX a better choice than Motorola's 755.

The 750CX was first used in the second-generation iBooks, which ran at 366 MHz and 466 MHz.

PowerPC 750CXe

IBM introduced an enhanced version of the 750CX in 2001. The PPC 750CXe supported a 133 MHz system bus and reached speeds as high as 700 MHz. The 750CXe replaced the 750 starting with 500 and 600 MHz iMacs in February 2001.

IBM also improved floating point performance with this revision of the G3 CPU.

PowerPC 750FX

The next step forward came in 2002 when the PPC 750FX was designed to run on a 166 MHz system bus and at speeds up to 900 MHz. IBM doubled the size of the L2 cache to 512 KB, further improving the G3's efficiency. This was the last G3 revision used in Apple computers, possibly as early as the iBook 600.

PowerPC 750GX

Introduced in 2004, the PPC 750GX was IBM's last revision of the G3 design. The new version has a 1 MB L2 cache, could run on a 200 MHz bus, and topped out at 1.1 GHz. This CPU made its way into at least on upgrade for the blue & white G3, although Apple never used it.

Further Reading

Recent Online Tech Journal Columns

Links for the Day

Recent Content on Low End Mac

Recent Deals

About LEM | Support | Usage | Privacy | Contacts

Entire Low End Mac website copyright ©1997-2009 by Cobweb Publishing, Inc., unless otherwise noted. All rights reserved. Advice presented in good faith, but what works for one may not work for all. Please report errors to .
  LINKS: We allow and encourage links to any public page as long as the linked page does not appear within a frame that prevents bookmarking it.
  Access our RSS news feed at http://lowendmac.com/feed.xml.
  Email may be published at our discretion; email addresses will not be published without permission, and we will encrypt them in hopes of avoiding spammers. If you prefer your message not be published, mark it "not for publication." Letters may be edited for length, context, and to match house style.
  PRIVACY: We don't collect personal information unless you explicitly provide it. For more details, see our Terms of Use.
  Low End Mac is an independent publication and has not been authorized, sponsored, or otherwise approved by Apple Inc. Apple, the Apple logo, Macintosh, iBook, iMac, eMac, iPod, iPhone, PowerBook, MacBook, MagSafe, Mac Pro, Apple TV, and AirPort are registered trademarks of Apple Inc. Additional company and product names may be trademarks or registered trademarks and are hereby acknowledged.

Custom Search

Amazon.com

Navigation

Used Mac Dealers
Apple History
Video Cards
Email Lists

Favorite Sites

MacSurfer
MacMinute
MacInTouch
MyAppleMenu
InfoMac
Macs Only!
The Mac Observer
Accelerate Your Mac
RetroMacCast
PB Central
MacWindows
The Vintage Mac
   Museum
DealMac
DealsOnTheWeb
Mac2Sell
ramseeker
Mac Driver Museum
JAG's House
System 6 Heaven
System 7 Today
the pickle's Low-End
   Mac FAQ
Abandonware
   Petition
Mac vs. PC Info

Affiliates

The Apple Store
Mac Connection
B&H
MacMall
TechRestore
ExperCom
Crucial Memory
batteries.com

Advertise

All of our advertising is handled by BackBeat Media. For price quotes and advertising information, please contact at BackBeat Media (646-546-5194). This number is for advertising only.

Open Link

Problems viewing this page with Internet Explorer 5.5 or 6? It works fine in other browsers, including IE 7. We recommend Firefox for those using Windows, as it is standards based and more secure than IE 6 (and earlier). More LEM visitors use Firefox than any other browser.