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Power Macintosh G3/266 Processor Upgrade And Discussion Page - Performance Of Latest G3 & G4 Processor Upgrades

Power Mac G3/266 Facts at a Glance

  • G3 (750), 266 MHz
  • Bus Speed: 66 MHz
  • L2 Cache: 512K, backside @133 MHz
  • Installed RAM: 32 MB (768 MBMax)
  • RAM Slots: 3, 168-pin SDRAM
  • Min RAM Speed: 10 ns
  • Installed SGRAM: 2MB (Max 6 MB)
  • Drive: 4 or 6 GB EIDE
  • Internal Zip Drive, 100MB
  • CD Drive: 24X
  • Removable Drives: Floppy Drive, Zip Drive
  • Networking: 10baseT
  • Slots: 3 PCI, 1 COMM
  • Drive Bays: 1 (DT) 2 (Tower) external
  • Additional Ports: ADB, 2 Serial - Printer & Modem (modem port deactivated by Personality Card), SCSI
  • Supported MacOS: 8.0 - 10
  • Introduced: 8-5-97
  • Discontinued: 1/98
  • Initial Retail Price: $2,399, 2,999 (Tower)
  • Current Price
  • Has Personality card with 16-Bit audio in/out and internal modem (video in/out on the tower machine).
  • ATI 3D RAGE II+ graphics accelerator
  • Desktop model requires low-profile memory modules
  • Internal Zip drive takes up one drive bay on the Tower
  • There was a DVD drive option for these machines

PowerMac Upgrade & Troubleshooting
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The Power Macintosh G3/266 was part of the first generation of machines from Apple based on the new 750 PowerPC or G3 processor. It came in two flavors, the desktop and the minitower. For an additional $600 the tower configuration offered better storage capacity with a larger hard drive (6GB vs. 4GB) and an internal Zip drive for hauling those weighty graphics files around. Both machines came with a propriatary "Personality Card" which added functionality to the machine. The personality card in the desktop model provides 16 bit stereo sound in and out as well as a connector for an internal modem. The tower personality card offered these features as well as 24 bit video in and out.

When the G3/266 was first released MacAddict pitted it against an 8600/300, a machine with a 604e processor running at 300MHz. They found the G3/266 completed a suite of Photoshop functions 78% faster than the 8600. NortonUtilities gave the G3 a score roughly 30% higher than the 8600. These scores reflect the advantages of the G3 over the 604e chip. The G3 chip found in the 266Mhz desktop model was a faster version of the PowerPC processor. It's speed was enhanced because the L2 cache resides on a dedicated backside bus running at 133Mhz between processor and cache. Previously L2 cache performance was limited by the speed of the main logic board bus which runs at a much slower speed.


The processor and cache reside in on a removable card that fits into a PC type Zif socket making it easy to replace with a faster processor. The main system bus of these G3 machines runs at 66Mhz (the previous Macs ran at 50Mhz). The G3/266 comes with 32MB SDRAM, expandable to 768 MB using the 3 DIMM sockets (standard profile 128MB DIMMs will not fit in the desktop machine). The graphics controller is the ATI 3D Rage II+ and the machine came standard with 2MB SGRAM graphics memory which allows for millions of colors (32-bit) at up to 832 x 624 resolution. Graphics memory is expandable to 6MB which will allow millions of colors at higher resolutions and faster 3D performance. There are 3 PCI slots for add on cards and a proprietary slot for the included personality card. The hard drive is a 4GB EIDE on the Desktop and 6 GB on the Tower, and the CD ROM is 24x. The Tower machine has one free 5.23" drive bay (the other is filled with the internal Zip drive) and both machines have external SCSI connectors (5Mbytes per second). The machine case is easy to get into and the simplicity of the new logic-board design make upgrades a snap.

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Below you will find the MacBench 5.0 results for most of the processor upgrades available for this machine.

** Note that MacBench does not take advantage of the Velocity Engine (AltiVec instructions) of the G4. For AltiVec accelerated applications you can see a 1.4 to 4 times performance improvement over the G3, depending on the application and the functions you are trying to perform.

"But I thought that the G4 was so much faster than the G3?" In some cases it is! For G4 Application specific scores - Click Here

MacBench Absolute Scores

Processor Upgrade Card

MacBench 4.0 Processor Score

Power Macintosh G3/266 895
XLR8 MACh Speed MPe G4/400/200/1MB 1186
XLR8 MACh Velocity MPe Dual G4/400/200/1MB
PowerLogix PowerForce G4Z/400/200/1MB 1243
Sonnet Encore G4/400/200/1MB 1252
XLR8 MACh Speed G3Z/400/200/1MB 1314
XLR8 MACh Speed MPe G4/450/225/1MB 1335
XLR8 MACh Velocity MPe Dual G4/450/225/1MB 1335
PowerLogix PowerForce G4Z/450/225/1MB 1398
XLR8 MACh Speed G3Z/450/225/1MB 1478
XLR8 MACh Speed MPe G4/500/250/1MB 1483
XLR8 MACh Velocity MPe Dual G4/500/250/1MB 1483
XLR8 MACh Speed G3Z/466/233/1MB 1531
Sonnet Encore G4/500/250/1MB 1565
XLR8 MACh Speed G3Z/500/250/1MB 1643
Sonnet Encore G3/500/250/1MB 1679
PowerLogix PowerForce G3Z/500/250/1MB 1680