G3 & G4 SDRAM!

Model number links below point to logic board diagrams elsewhere on this website. The diagrams may be useful to experienced Macintosh users in identifying significant motherboard landmarks and memory expansion slots. If you do not see a diagram for your Macintosh and need assistance, feel free to email a MacGurus support engineer. If you are in doubt about your ability to handle sensitive electronic components, please contact your local authorized Apple dealer. Don't void your warranty!

Note: All 168-pin PC100 SDRAM DIMMs listed on this page are high-quality 3.3-volt, unbuffered "2-2-2" SDRAM, fully PC100-compliant, 64-bit-wide, with a speed of 125MHz/8ns or faster. These SDRAM DIMMs feature a properly programmed 256-byte Serial Presence Detect ROM for perfect compliance with Apple specifications. Two inches in height (or less), these SDRAM DIMMs have been specifically engineered for use in Yosemite, Yikes G4, and original Sawtooth, and incorporate 64 Mbit parts in 32MB and 64MB pieces, and 128 Mbit parts in 128MB and 256MB pieces. (Low-profile Sawtooth 256MB SDRAM is 1.25-inches in height, and appropriate also for improved iMac, aka iMac DV.)

Apple Power Macintosh G3 and G4 released before January, 2001 are compatible with 3-2-3, 3-2-2, and 2-2-2 PC100 speed codes, though MacGurus ships only genuine 2-2-2 SDRAM for enhanced compatibility with G4 processor upgrades which are entering distribution channels at this time and to optimize memory bandwidth and performance. While Yosemite, Yikes and the original Sawtooth query the presence detect ROM for memory timing settings of all memory installed, and throttle down for compatibility with the slowest installed device, mixing speed types generally inflicts only a minor performance penalty. Please be advised that Apple has historically shipped older Apple G3 and G4 with 3-2-3 or 3-2-2 SDRAM preinstalled, though faster PC100 Sawtooth did frequently ship with all 2-2-2 SDRAM, including the 500MHz G4, G4 Multiprocessor, and the Power Macintosh Cube. The improved G4 Digital-Audio Sawtooth released in January, 2001 is a special case, and will be discussed below. In any case, G3/G4 SDRAM is compatible with all factory-installed SDRAM in all configurations.

It must be noted that Apple released G4 Firmware Update 2.4 to fix a bug that arises when more than 1GB of main memory is installed in the original Sawtooth. Previously, SDRAM auto-refresh was set by firmware at 15mSec. Higher density SDRAM with 7mSec refresh was often problematic as a result. This important update makes it possible to use denser 512MB SDRAM DIMMs, and is strongly recommended for all original G4 Sawtooth owners. This functionality has been integrated into the updated firmware in the improved Sawtooth Digital-Audio G4, which is hence compatible with 512MB PC133 SDRAM out of the box. The easiest way to ensure that your Power Macintosh is running the latest firmware, regardless of when it was manufactured, is to use the Software Update control panel, featured in MacOS 9 and later variants, including OS9.1.

The Apple G3 Yosemite "Blue and White" and its G4 Yikes and original Sawtooth "Graphite" variants have four SDRAM expansion slots. No memory is soldered to the logic board, so at least one DIMM must be installed for these machines to boot. Apple does recommend that DIMMs be installed in slot 1 first (J19), then in J20, J21, and J22, in order. As the Grackle IC memory controller and PCI bridge on the Yosemite/Yikes and the Uni-North memory controller on the Sawtooth logic board support only linear memory organization, no benefit accrues from installing SDRAM DIMMs in matched pairs, and DIMMs (installed in any slot and any order) are addressed as a contiguous memory array. Originally, the max memory installable in Yosemite/Yikes/Sawtooth was 1GB, in the form of four (4) 256MB 128Mbit pieces. With the release of G4 Firmware Update 2.4 (5-26-2k), memory configurations up to 2GB are physically conceivable in original Sawtooth using four (4) 512MB SDRAM DIMMs. Due to limitations in MacOS 9.04 and OS9.1, the max memory configuration useable at this time is 1.5GB. No, we have not yet tested in all possible configurations in all machines. In fact, we just recently confirmed that it is not possible to run a Yosemite or Yikes with memory beyond 1GB. The densest pieces that work in Yosemite and Yikes--and yes, Beige G3--are 256MB. We have confirmed the 1.5GB limitation in Sawtooth G4 500 under MacOS9.1 with Firmware Update 2.4 using three 512MB SDRAM DIMMs. Reports from the field are welcome.

As mentioned, the improved Digital-Audio G4 Sawtooth is a special beast. This variant of the latest G4 has only three DIMM slots, yielding a maximum configuration of 1.5GB using three PC133 512MB SDRAM DIMMs. No memory is soldered to the logic board, so at least one DIMM must be installed for these machines to boot. As the Uni-N memory controller on the improved Sawtooth logic board supports only linear memory organization, no benefit results from installing PC133 SDRAM DIMMs in matched pairs, and DIMMs (installed in any of the three slots and in any order) are addressed as a contiguous memory array.

Unlike earlier M6709LL/A and M6709LL/B iMacs, the iMac, iMac DV and iMac DV Special Edition require PC-100 DIMMs. The new improved "AirPort-capable" iMacs have two DIMM slots and support PC100 SDRAM DIMMs in densities of 32MB, 64MB, 128MB and 256MB, with a maximum DIMM density of 256MB per slot for a total maximum memory capacity of 512MB. We emphasize that only "low-profile" 256MB SDRAM DIMMs are compatible with the improved iMac. They require the lower 1.25-inch form factor. As of June, 2000, all SDRAM sold via this page will fit. We have not yet confirmed compatibility of 512MB SDRAM in iMac DV. Again, reports from the field are welcome.

With the exception of the improved iMac, Apple G3 and G4 main logic boards lack video memory, and Yosemite/Yikes/Sawtooth requires its standard 16MB ATI Rage 128 video card (or Rage 128 Pro, Radeon, or NVIDIA G3Force2, in the case of the improved G4 Audio Sawtooth) to function. VRAM on the video card is not upgradable.

All listed PC100 pieces are fully compliant with Apple Yosemite/Yikes/Sawtooth/iMac DV specifications, including form factor, which is 2-inches (or less), 256MB DIMMs excepted. Again, in the event you are confused, all PC100 memory sold via this page after June, 2000, is by definition "low profile," and will physically fit all Yosemite, Yikes, original Sawtooth, and iMac DV. PC100 DIMMs listed on this page are appropriate for use in the "Blue and White" versions of the Apple G3 Yosemite, the "Graphite" Apple G4 Yikes and original Sawtooth variants, and the "improved" iMac DV, and are engineered to support their faster logic board bus speeds of 100MHz.

LIkewise, all listed PC133 SDRAM is fully compliant with Apple improved G4 Digital-Audio Sawtooth specifications, including form factor, which is 2.0 inches or less. SDRAM is not adversely affected by Apple's Firmware Update 4.1.8, which disables SDRAM with incorrectly programmed serial detect EEPROMs. If you would like to test your memory for compatibility, Glenn Anderson's DIMMCheck and DIMM First Aid are available on our FTP site, along with several other memory testing utilities. PC133 SDRAM is engineered to support both the 133MHz clock and MaxBus protocol of the improved Sawtooth logic board.

Yes, you can use most PC100 and PC133 SDRAM in minitower (MT) revisions of the Beige G3, and it does generally work well with G3 and G4 processors, including dual-G4's, running at 500MHz and faster. PC133 G3/G4 SDRAM in densities up to 256MB is compatible with G4 upgrades from third-party manufacturers installed in MT Beige G3. We have confirmed that 512MB SDRAM DIMMs are not compatible in beige G3. The max configuration for beige G3 is 756MB, attained using three 256MB SDRAM DIMMs. Larger 512MB SDRAM DIMMs will not work in Gossamer or Artemis logic boards.

Be advised that the form factor limitation of 1.25-inches in the desktop (DT) versions of the Beige G3 precludes the use of earlier 2.0-inch SDRAM in those variants, with the one-time exception of the 256MB "low-profile" SDRAM DIMM. As of June, 2000, all memory listed on this page up to densities including 256MB will physically fit and work beautifully in all beige G3, including desktop (DT) configurations.

Chip-sets used vary, but G3/G4 Yosemite SDRAM DIMMs invariably work error-free in the Power Macs listed below.

The DIMMs on this page are specifically designed to support: