You can "roll your own".
This old
Apple Hardware Technote describes how Macs with the two row 15Pin D-Sub connector works.
When you turn on your Mac, it checks 3 pins on the video connector to see how they're wired. The combinations were originally 2x2x2 or 8 codes. In this way, the Mac knows what model monitor is attached and hence what resolutions that monitor can do. This was extended later by wiring pins via diodes as well to extend the number of combinations.
I usually select the 16" Multiscan, (which also represents a 17" Multiscan). This gives you 640x480, 832x624, & 1024x768 at scan rates that most Vesa SVGA monitors can handle (most 15-17" CRT & LCD monitors).
Tie pin 4 to ground and place a diode (a
1N4148 or 1N914 will do) from pin 7 to pin 10. The black stripe on the diode should be at the pin 10 side. (see "Figure 4" on the linked page - NOTE the numbers in that figure refer to SENSE line numbers, NOT the connector pin numbers).
Wire all the other pins red(2), green(5), blue(9), VSync(12) and Hsync(15) thru to the matching pins on the 3 row 15pin D-sub SVGA connector. Wire the ground (GND) pins thru to the appropriate GND pins on the SVGA connector. See
this pic for the SVGA Pinouts. Don't wire anything to the "ID Bit X" or "DDC" pins on the SVGA connector.
This gives you the above resolutions only but there's little reason to go much higher IMHO.
Confused? Buy the adapter noted above from eBay which is simpler, really!
PS: LCD monitors look best at their HIGHEST resolution so 1024x768 on a LCD with a highest resolution of say 1152x870 will look fuzzy. A CRT should look fairly crisp at ANY resolution.
