Don't disregard your PPC card as dead just yet. The two clock jumpers must be set to EXT position. The card doesn't boot when those jumpers are set in INT.
Also, it could be that CSPPC makes bad contact, or not as good as A3640 with your motherboard's cpu slot. If possible, try testing your PPC card in another A4000.
2 things. It could be that your motherboard has a flakey fast slot connector and that affects the CSPPC, but is good enough for A3640, and it could also be that CSPPC comes with a flakey connector which just doesn't sit right when inserted in the CPU fast slot.
I hope that your card is fine afterall! :-)
edit:
Also, your card will not boot if the simms installed are not paired properly. Install a matching simm in ever other slot. For example:
0 -> 32MB Brand A
1 -> 16MB Brand B
2 -> 32MB Brand A
3 -> 16MB Brand B
Make sure to get matching simms for best results! The above rule is a must. Also, CSPPC needs some memory on it in order to boot. Remove motherboard memory and try booting just with CSPPC memory.
Try holding ESC on boot and see if you get the CSPPC early boot menu.
