J21 vs. J24 for empty DIMM slot in G4-450 AGP

[Richard Kriss]

For reasons I don't understand a PC user wanted to trade me his PC-133 256K
DIMM for two of my PC-100 128K DIMMs.  Sounded good to me and we swapped.
My G4-450 AGP accepts either PC 100 or 133.

Before the swap I had the G4 configured:

DIMM1/J21 SDRAM 128 MB
DIMM2/J22 SDRAM 256 MB
DIMM3/J23 SDRAM 256 MB
DIMM4/J24 SDRAM 128 MB

After the swap I have the G4 configured:

DIMM0/J21     =     empty
DIMM1/J22 SDRAM 256 MB
DIMM2/J23 SDRAM 256 MB
DIMM3/J24 SDRAM 256 MB

Should I have left J24 empty rather than J21 or does it really matter?  It
seems to work okay and the DIMM first aid says everything is Okay.

I'll probably get another 256 or 512 to fill up the G4-450 sometime soon.

When I ran the DIMM First Aid (that only runs under OS9), it said one of my
old PC-133 DIMMS was okay but added a note that CL2 not supported. What does
'CL2 not supported' mean?

Dick