I have the following config:

Dell OptiplexGX1p
PentiumII 450MHz
128MB RAM
Seagate SCSI 9GB - BOOT drive
Zip100 drive - Primary Master
Western Digital EIDE 80GB (Data only) - Primary Slave
TDK CDRW40/12/48 - Secondary Master
Samsung 40X CDROM SC-140B - Secondary Slave

I'm using Nero 5.5 to do CD Copy w/on-the-fly option enabled. A burn at 24X took 12 minutes, but both read and CDRW buffers never maintained levels above 90% except at startup. Is this the optimal setup? I've read other suggestions and tried separating the CDROM and CDRW on different channels, but it resulted in either system crashes, or EXTREMELY long burn times. Please help!!!

if i read correctly, are your reader and writer on the same ide? if so, then ofcourse you'll get major slowdown (even resulting in buffer underruns). set the writer as master on one ide, and the HD and reader master and slave on the other. never do any data transfer over the same ide. about those crashes, i don't know. i have a hd that doesn't work when puttting it together w/ my cdrom drive, don't know how that comes either. I ended up buying a scsi recorder.

Yes, I have the writer and reader on the secondary IDE controller. The funny thing is, I get better success completing CD copies with it this way. But you're suggesting I put the writer on the Primary IDE as master, and the HD and reader as master and slave on the secondary? My last resort is to buy a Ultra66 or 100 IDE card for more options.

yes you could... but if I were you i'd try to figure out what caused these system crashes. Perhaps all it is is a misplaced jumper or so, perhaps let a pro check out your pc, i don't know... instead of going at once for additional ide cards. three devices on 2 ide channels are generally no prob. Hope you get it all to work.