Electrically, the Power Macintosh Desktop can support 384MB of memory, using three low profile 128 MB DIMMs. Without low profile 128 MB DIMMs, the computer is limited to three 64 MB DIMMs for a total of 192 MB.
Note: Power Macintosh G3 computers (Desktop and Minitower) that have revision 3 logic boards can support 256MB DIMMs for a total of 768MB of installed RAM. Refer to Kbase article 24924: "Power Macintosh G3: Identifying The Logic Board Revision" to identify which logic board a Power Macintosh G3 came with.
Some third party vendors have redesigned their 128MB DIMMs to be slightly shorter and to fit in the desktop case. If the developer has followed the electrical JEDEC specification and verified the design and functionality for the Power Macintosh G3 Desktop, then these shorter DIMMs should work without issue in the Power Macintosh Desktop G3.
In addition, it is the responsibility of the third party manufacturer, not Apple, Inc., to verify the design and ensure the reliability of their memory modules, including standardized parts, designed for the Macintosh.