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

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.

Second Class Macs & Road Apples

Power Mac and Performa 5200-53xx & 6200-6320

four

Dan Knight - 1998.01.10

Road Apples are Apple's most compromised hardware designs. For the most part, they're not completely bad - simply designs that couldn't meet their potential. (On our rating scale, the more brown apples, the worse the hardware.)

This entire series of PowerPC-based Macs suffered from the most bizarre motherboard architecture Apple ever devised and is perhaps the most deserving recipient of the Road Apple title.

To save time and money, Apple chose to build these on a modified Quadra 605 (a.k.a. LC 475) motherboard - which was a fine design for a 25 MHz 32-bit 68040 CPU. (They also used some Quadra 630 parts - as well as its case for the 6200-63xx.) However, the PPC 603 is a 75 MHz or faster 64-bit CPU.

You'd think Apple would have learned its lesson with earlier Road Apples (the LC, LC II, Classic II, Color Classic), all of which coupled a 32-bit CPU to a 16-bit data bus. But no, they did it again, this time hobbling a CPU with a 64-bit bus on a 32-bit motherboard.

Apple went beyond crippling the 64-bit CPU on a 32-bit data bus - way beyond that.

  1. Depending on CPU speed, memory runs at one-half to one-third CPU speed. (Because RAM is so slow compared to current CPUs, this is normal for Power Macs. In fact, the G3 can run at up to 8 times motherboard speed. If this were not possible, we'd still be living with computers running under 200 MHz.)
  2. It takes four memory cycles to load a 64-bit word (which equals 8-12 CPU cycles, since the processor is two-to-three times faster than memory!). Cycle 1: read 32 bits. Cycle 2: store 32 bits. Cycle 3: read next 32 bits. Cycle 4: combine with first read for 64-bit instruction. Then the CPU can process the instruction.
  3. Because it used a 32-bit motherboard, different functions were handled by different 32-bit buses, called Left 32 and Right 32.
    • Left 32 handled networking, audio, ADB, and SCSI. Networking, audio, and ADB are each 16 bits wide; SCSI (for CD-ROM and external devices) is 8 bits wide. This involves a lot of overlap and causes a lot of problems.
    • Right 32 includes the 32-bit memory controller, the 8-bit IDE controller (for the hard drive), the 32-bit graphics controller, the 16-bit video controller, and the (thankfully optional) 8-bit TV controller. Again, this involves a lot of overlap and can cause a lot of problems.
    • Any time something on Left 32 needs to communicate with Right 32, or vice versa, it must go through the CPU, which acts as a bridge. This really slows down the CPU, since it must divert its attention from processing data to moving data between sections. And don't forget the four-cycles-per-64-bit-word problem noted above.
    • Because of the design, all data from the serial port, comm slot, or an ethernet card must pass though the CPU to reach RAM. This makes these very poor performers on the internet.
    • Because of this peculiar architecture, upgrading the level 2 cache or increasing VRAM would slow things down. Good thing they aren't options.
  4. Apple saved money by using IDE hard drives instead of SCSI drives. Not only is IDE cheaper, but cheap IDE drives tend to be slower than cheap SCSI drives. (Today this is not the issue it once was. The Blue Power Mac G3 has a very fast IDE drive.)
  5. Again to save money, Apple left hardware handshaking off the serial ports. These were the only PowerPC-based Macs without GeoPort serial ports. (Even the Mac Plus had hardware handshaking!) This limited users to a comm slot modem or a 9600 bps or slower external modem.
  6. A comm slot modem disables the modem port; a comm slot ethernet card disables the printer port.

Because of their unusual architecture, installing a 25-pin SCSI terminator to the SCSI port (if you have no SCSI devices attached) will improve network stability.

The poor benchmark performance of this series gave the PowerPC 603 chip a black eye. It wasn't the chip that was at fault, for it was more efficient than the PPC 601. It was the horrible architecture of this system that made the 603 a chip-non-grata until the 603e came out on Macs with better designs.

Overall, the design compromises make these Macs to be avoided at all costs. But also remember that there were several different versions of some of these models, both ongoing revisions and models created for other markets. Some later motherboards fixed some of these problems.

For a different perspective on serial throughput on the x200 series, see Modem performance using FreePPP and OT PPP on at 5320 by Adrian Winnard. It should also be noted that reports from the field indicate that Mac OS 8.1 and later smooth out a lot of issues these models suffer from. LEM

Details

Cautions

Other Resources

Links for the Day

Recent Content

Recent Deals

About LEM | Support | Usage | Privacy | Contacts

Entire Low End Mac website copyright ©1997-2010 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

Low End Mac's Amazon.com store

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.