Curiously, I pulled out one of my dismantled iBook G3 700MHz units and have the same findings as
@ApplePearGrapefruit. I've never actually upgraded to SSD in these models, so I hadn't come across this incompatibility before.
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The HDD/CD-ROM ribbon cable pin arrangement from the 700MHz iBook G3 appears to match the 500MHz model in first post, however the pins are filled from factory rather than being plugged with a putty as also shown in first post. It doesn't make a difference, but just an observation.
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The pin block is accommodated for on a regular 2.5" IDE HDD from this era...
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But attempting to connect an mSATA to IDE adapter shows the board/housing are obscuring the pin block.
Let's mod!
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You could modify your adapter/housing, but I opted to mod the pin block because those two outer pins are clearly unused, and just getting in the way...
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Carefully cut the last two (blocked) pins of the plastic block away. Do not damage the ribbon!
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I discovered there are two inaccessible pins under the block here. I bent them down in the photo here.
Be careful not to cut into the adjacent cells.
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Bend the superfluous pins back and forth a couple of times and they'll cleanly snap off.
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We can now connect the mSATA to IDE adapter!
Let us know how you go