After several days of trying to coax reliable results out of my Pioneer DR-US124X CD drive on the CQD-220, I finally gave up and acquired a proper Plextor drive. The Pioneer had various issues, some of which may just be due to it being in bad shape - I'll have to test it out on some of my Macs to see if that's the case. In case anyone stumbles upon this in an archive, I thought I'd list the symptoms: - After it warmed up, it would throw errors when operated in sync mode, even in the CQD-220's built-in drive test - When not in sync mode, it would work on the built-in test, but would periodically just stop responding. VMS would eventually (after a good 5 minutes or so) give up and declare it "not software enabled". This had an annoying tendency to happen during lengthy installs. - All the other drives in the SCSI chain (a hard drive, a Zip drive and a Jaz drive) seemed to work just fine, so I'm relatively sure it wasn't a termination issue. And yes, the drive was jumpered to 512 byte blocks. It would boot the VMS install CD without the jumper, but it would never proceed to executing the standalone BACKUP program. Someone was selling a 20x Plextor drive on eBay for a pretty good price, so I snapped it up. It's worked 100% reliably since I plugged it in. Perhaps their SCSI implementation is more compliant? All I know is that they have an extremely good reputation, and their user manuals seem to be cognizant of the various reasons you might want to run in 512-byte block mode.