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Inside  the PowerBook G3 "Wallstreet" - Adding Ram
Published: June 1998


Now you can see the main access area to the motherboard and hard disk. To access the ram expansion slot, you'll have to remove the flat metal CPU heatsink in the center of the open area. The heatsink is retained by two screws (philips head) and Apple has thoughtfully provided a thin wire lifting handle into the heatsink (nice touch).

Heatsink screws identified
CPU Heatsink Retaining Screws

Once the screws are removed, grasp the wire lift handle and lift it up to release the heatsink, pulling it toward you once the edges are clear. In case you're interested, I took closeup photos of the top and bottom of the heatsink. The bottom of the heatsink has conductive pads that isolate the CPU from shock and vibration while still allowing heat to be conducted away from the G3. Notice the round conductive disc on top the CPU, which contacts the pad on the bottom of the heatsink.

Removing the CPU Heatsink
Lifting out the CPU Heatsink

With the heatsink removed, the main internal components are exposed. I've labelled the CPU, cache, PCI to Cardbus controller and HD. Just forward of the PCI chip and CPU is the modem (Rockwell/56Flex based).

Internal PowerBook Internals
PowerBook Internal Components

Now that the heatsink is removed, to the right of the CPU is the ram SODIMM slot. You simply insert the ram dimm, pressing firmly to make sure the contacts are fully seated, no contacts should be visible peeking out of the socket. The retaining dimples cut in the side of the dimm will be aligned with the locking tabs in the powerbook when its fully seated into the socket, then you simply press down to snap it in place. DO NOT FORCE IT. Any severe resistance is a sign that the dimm is not fully seated into the socket.

ram installed
Ram Locked and Loaded

Reassembly is simply reinstalling the heatsink, securing it with the two screws and replacing the keyboard by aligning the metal tabs on the rear edge of the of the keyboard with the grooves in the case. Slide it in and lower it down, pressing on the front edge to snap it in place.

Now simply put your expansion bay devices back in and you're done!


Finishing Up - Software Settings:

Power-up and immediately turn off Virtual Memory in the Memory control panel, restart and get ready to notice a real difference in performance. Don't forget to allocate more ram to those resource hogs like Photoshop - it makes all the difference in the world. You might want to increase your disk cache as well, but beware Photoshop likes smaller (minimum) disk cache sizes (based on PS 4 and earlier and I assume v5 as well).

Even finder operations are noticeably faster with the extra ram.

(NOTE: The PB G3 "Wallstreet" (and later Lombard model, as well as iMac G3/233-333MHz, Beige G3 and B&W G3) use a memory controller that is limited to a max dimm/sodimm size of 256MB BUT ONLY if the module is made from 128Mbit chips. (The memory controller in these models has a limit of 128Mbit chips and 16 chips per dimm - for a Max of 256MB per module. Note that many 256MB modules are made from 256Mbit chips (x8) and therefore will not be fully recognized (they will be seen as 128MB modules). Some Mac savvy vendors sold compatible 256MB modules, although again most common ones are 256Mbit chip based. The last source for low-profile, 256MB SODIMMs for PB G3 Wallstreets/Lombards/iMac G3 233-333MHz models is OWC.)


PowerBook G3 vs Gateway Solo PII notebook: I've also posted a comparison review between the PB G3 and the PII Gateway Solo - design/ease of use, layout and performance comparisons are done with some surprising results. Check it out.


Some Component Details of the "Wallstreet" PB G3/250:
  • CPU: Motorola/IBM PowerPC 750 at 250 MHz
  • Cache: Motorola MCM69P737ZP3.8 (1 MB)
  • PCI Controller: Motorola MPC106 (same as desktop G3)
  • PCI to Cardbus Controller: TI PCI131PDV
  • Modem: Rockwell RCVDL56DPFL/SP
  • OEM Memory: Hitachi 10ns SDRAM
  • Bus Speed: 83 MHz (for G3/250)
  • Screen: TFT (Active Matrix) 1024x768 (fixed)
  • Video Ram: 4MB 10ns SGRAM (Sync. Graphics Ram)

Cache Notes: The PB G3/250 appears to have the same cache chips used in the Beige G3/300 desktop. The Motorola part number (MCM69P737TQ3.8) specs are: 3.8 ns access, 6.7 ns cycle time, rated for 150 Mhz according to the Motorola data sheet. The parts are Motorola's 128K x 16 Bit, pipelined BurstRam Synchronous fast static rams. These Motorola parts integrate input registers, an output register, 2 bit-address counter and SRAM into one device for lower assembly parts count.

Other PowerBook Related Articles:

  • See the Systems Page, PowerBook section for drive upgrade guides, CPU upgrade reviews and more.


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