Upgrading the VRAM in a Quadra 950

So you have a lovely Macintosh Quadra 950 with only the onboard 1MB of VRAM, and you want to upgrade it to the full 2MB? Here’s how.

Firstly you will need 4 sticks of compatible VRAM. These come in either 256K or 512K sizes. While you can use 512K sticks, only 256K will be visible to the system, so a bit of a waste.

Make sure you observe Anti Static precautions for the next few steps. At a bare minimum, make sure you are earthing yourself to the metallic parts of the system chassis while you work. Better yet, use an ESD workstation. (My entire desk is an ESD workstation)

Open the side panel with the two press in latches at the back and swing it open from the back edge.

Side panel removed

Now unplug the 50 pin SCSI ribbon cable from the board (It has two levers on each end that pivot out and backwards that will assist you with this task. Try and move them out at the same time), unplug the power lead to the motherboard (There is a clip that needs to be pressed in at the top to release it), the drive power leads (These also have a clip like the power lead to the motherboard) and the floppy drive ribbon cable. (Despite the difference in size, it comes out just like the SCSI cable).
Fold the cables up and out the way. Don’t worry about this with the motherboard power cable.

Now, on the top metal rails between the drives and the power supply, remove the outer two visible screws. There is a concealed screw behind the front fascia, but we’ll get to it shortly.

Cables folded back and outer screws removed.

Now slide the entire upper drive assembly towards the back of the case. There’s a little thumbrest near the back that can assist. Remove the drive assembly and put aside.

Next you need to remove the front fascia. First, unplug the speaker. It simply unclips from the two pins it’s connected to. There are two plastic clips in the middle of the fascia that protrude into the case. There are another two underneath the system.

Carefully lever the clips away so that you can remove the fascia. Just be aware, these plastics are up to 30 years old, and can be quite brittle. Take it gently!

Fascia removed.

Once the fascia is gone, there are three screws (Two at the back and one at the front) to remove to allow the power supply to come out. Once they have been removed, the power supply can be lifted straight up and out by the cable ties through it.

One at the front, two at the back.

With the power supply out the way, you can now reach the VRAM slots. they’re the 4 white ones at the top.

Starting with the uppermost SIMM socket, place the VRAM SIMMs in with the chips facing the top of the board (assuming 256K SIMMs. For 512K simms, put the side marked “256K” facing the top) in at about a 45 degree angle, and slowly, applying a pressure towards the point the SIMM meets the socket, lever the SIMM to vertical, making sure both metal clips engage.

Once all four are populated, you can start buttoning the whole system back together. It’s pretty much a reverse of disassembly. The only trick I can suggest is that while inserting the power supply, it’s easiest to get the front guide in the “L” shaped guide before getting the back part lined up. Don’t forget to plug back in the speaker.

Power on and you now can use 24 bit colour in all but the highest resolutions. Those now support thousands (16 bit) of colours. Enjoy your new Macintosh setup.

Published by ilike8bits

I collect old computers and consoles

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