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.

Mac Musings

Should Apple Use the New G3?

Dan Knight - 16 June 2000 - Tip Jar

There's been some interesting discussion of IBM's new PowerPC 750CX and forthcoming 750CXe processors, especially related to IBM discusses new PowerPC chips on MacWeek. A lot of Mac users seem to think the 750CX would be a poor choice; I beg to differ.

PowerPC 750CXThe biggest difference between the 750CX and the old 750 (commonly known as the G3 in Macintosh circles) is the integrated 256 KB level 2 (L2) cache.

External L2 Cache

The old 750 supports an external L2 cache in sizes of 256, 512, and 1024 KB. Apple has only produced one model, the "Road Apple" PowerBook G3 Series I at 233 MHz, which has used the G3 without a cache - and performance suffered significantly in comparison to the later PB G3 Series II 233 MHz model which did include a cache.

IBM has provided some comparisons for the G3 with various cache sizes. The numbers are rounded off, but a G3/400 with a 256 KB 200 MHz L2 cache* and a 100 MHz system bus (the configuration of the Yosemite G3/400) scores approximately 15 using the SPECint95 benchmark. Doubling the L2 cache to 512 KB increases that to roughly 17, and going to a 1 MB L2 cache brings the SPECint95 score to about 18.

* Note that some less expensive Macs run the cache at only 40% of CPU speed. This provides lower performance than a cache running at 50% of CPU speed.

With the old G3, the PowerBook G3 demonstrated that a 512 KB L2 cache improved performance by about 40%. Thus, a G3/400 with no L2 cache would be expected to score about 12 on the SPECint95 benchmark. Adding a 1 MB L2 cache improves that by about 50% - very impressive.

Internal L2 Cache

The new G3 (750CX) doesn't use an external L2 cache. The internal cache is 256 KB in size and runs at full CPU speed, giving it a distinct advantage over the external 256 KB L2 cache. In fact, IBM has benchmarked the 400 MHz 750CX at 16 using SPECint95. That's one-third faster than a cacheless G3, about 6.5% faster than the old G3 with a 256 KB cache, and about 6% slower than the current G3 with a 512 KB cache.

Of course, the G3/400 came with a 1 MB L2 cache, so the 750CX won't quite match it's performance. In fact, it will be about 12% slower - but a 450 MHz 750CX will match the performance of a G3/400 with a 1 MB external cache.

All of this closely matches IBM's theoretical analysis, which points to the 750CX being 6.5% faster than a G3 with a 256 KB cache. The same theoretical model points to a 512 KB internal L2 cache offering an insignificant (1.5%) improvement over a 256 KB cache.

The Benefits of 750CX

I believe Apple should adopt the new IBM processor for the iBook, iMac, and PowerBook. It may not match the performance of a G3 with a larger external cache, but it has the following benefits:

  • The 750CX uses less power than the 750, about 4W at 400 MHz vs. 7W.
  • An external L2 cache draws power, reducing battery life in a portable. The 750CX doesn't use an external cache.
  • Putting a G3 along with L2 cache chips and other support circuitry is an expensive process. With the 750CX, there's just one chip to plug in, reducing complexity.
  • It's also less expensive to buy the 750CX than a G3 plus cache chips plus the board they sit on.
  • Today's computers are plenty fast. Being 5-15% slower than some theoretical maximum is virtually unnoticeable.

Based on IBM's data, a iBook with a 750CX at 400 MHz would be about 25% faster than the current 300 PowerPC 750CXMHz model and roughly equal to the iBook SE in performance while using a less expensive processor that draws less power. Likewise, a PowerBook with a 750CX at 550 MHz would offer comparable power to the PowerBook 500 while reducing power consumption.

In the end, Apple would benefit from moving to the 750CX for their consumer line. It will reduce costs, making these machines even more affordable, increase battery life, and give Apple a boost in the megahertz wars.

That's something work discussing, especially in the engineering and marketing departments. LEM

Update: On Sept. 13, 2000, Apple announced the second-generation iBook and iBook SE, both running the 750CX processor. Apple managed to trim US$100 from the iBook's price while boosting CPU speed and adding FireWire. The iBook SE received a DVD-ROM drive and faster processor with no change in price.

Further Reading

Dan Knight has been using Macs since 1986, sold Macs for several years, supported them for many more years, and has been publishing Low End Mac since April 1997. If you find Dan's articles helpful, please consider making a donation to his tip jar.

Recent Mac Musings

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.