This is something I don't know enough about!! A customer complained of his 32-speed CDROM freezing his computer when he inserted an audio CD. The request wasn't to sort out this problem per se as he imagined it was a software glitch. The computer had become pretty well filled up with stuff and it's always a good idea to periodically start again from scratch. All sorts of weird problems disappear when a fresh operating system has been installed. This is mainly because out of date DLLs and EXE files that came in via freebees off magazines and suchlike and plonked their own program files in Windows System are replaced with proper versions. That's not to mention the odd undetected virus lurking around as well, also vanishing when the hard drive's been FDISK'd and reformatted. Computers start up faster, no longer freeze up and shut down cleanly when the hard drive's been reformatted and reloaded. That's what we thought anyway. Incidentally I don't believe anything short of a reformat will fix a badly errant machine completely and SFC is often confusing and only helps in isolated cases of lockups etc. A Windows Re-install sometimes helps but hardly ever.
Back to the example being described. The original configuration had a 10 gig hard drive as Primary Master, a R/W CDROM as slave and a 32 speed CDROM as Secondary Master. The BIOS which came with this "Times" machine had a page where one was supposed to identify items plugged into each IDE bus. The R/W CDROM was missing here as the last installer hadn't noticed the options. The customer requested that this drive be removed and a new x16x8x40 Yamaha R/W drive fitted. I fitted it on the Secondary bus as Slave to the x32 drive. After reformatting the hard drive Windows 98 loaded fairly smoothly. The only problem was identifying the modem. As with most new internal modems they are not recognised by Windows until partly installed manually. Having half-finished the manual installation Windows kicks in with its two pennyworth. Usually you end up with two modems installed. One won't work and the other will. The one labelled #2 is invariably OK. Then the "wave" bit can't be detected. You can tell it were it's to be found but you can't get it to be picked up. Sometimes after a dozen attempts it will suddenly click and in it goes. To remove the #2 it's best to remove the first one (the one that doesn't answer its diagnostic test) and the #2 and start again. This time it may get picked up as a plug and play device and all the drivers will fall into place automatically including the Wave bit. I guess it's something in the Registry that makes the PnP work second time around.
Anyway Windows went in OK and I started testing various programs. Nero would not work. It could see both CDROMs but it kept falling over when an audio CD was inserted in the R/W drive. After a few attempts I noticed the IDE drivers had changed from three Ali motherboard types to two plus a generic Windows variety. Then whenever My Computer was selected the computer froze. After a few reboots the secondary IDE driver suddenly showed an exclamation mark. Then both CDROMs dissappeared from System. Try as I might I couldn't get them back. One dodge is to load MSCDEX etc into AUTOEXEC.BAT and a CDROM driver into CONFIG.SYS. This generally kickstarts them back in. Not this time. They were picked up during the MSDOS boot phase as D and E but vanished when Windows got underway. Even though they were sometimes missing in System they sometimes did appear in "My Computer". When this happened the R/W could be selected but the others ICON refused to illuminate. Very odd. After much fiddling I swapped the IDE drivers by deleting them and letting Windows put them back in then both CDROMs suddenly reappeared. Unfortunately "My Computer" froze again when it was double clicked and the disappearing trick etc. followed....ad nauseam...
I changed the two IDE cables and tried different combinations on the two ports with no luck.
The only recourse was to remove the x32 drive. Then everything worked perfectly but for some reason the DMA option has gone away. I think because the three Ali drivers haven't got the option whereas the Windows generic secondary IDE port one did.
The explanation for all this (I think) is that the motherboard cannot support two varieties of IDE interface on one bus. The hard drive appears to be UDMA33. The Yamaha CDROM is probably that also but the x32 drive may well be E-IDE or just plain IDE. I could have put the two faster devices on the Primary bus but this isn't a good idea for Writing CDs. It's best to put the hard drive on one bus and the R/W drive on the other. Of course it's always possible the x32 CDROM is duff. I've found that CDROMs are probably the least reliable bit of a computer .... I mean a newly assembled machine. By the time it gets to the customer the duff ones have been swapped for good ones.