Sun SPARCstation LX boot from CDROM?

About 20 years ago I rescued a fully working Sun SPARCstation LX with CDROM and QIC-150 tape drive - all 3 in lunchbox format - plus monitor when we moved office and management decided they no longer wanted/needed it. Shortly after I have installed an early version of NetBSD (1.3.3) from the CDROM drive. I played with it for a few days and then stored the entire system in a museum grade glass display cabinet. This is indoors with minimal dust and benign temperatures between 18 degrees C to about 28 degrees C (typical room temperatures here in Perth in Western Australia unless you run the air conditioner). Now retired I took the stack of "lunch-boxes" and the CRT monitor out of the display cabinet and powered it up. After 20 years no smoke came out but the system didn't boot but reported trouble with the NVRAM setting. I still could start NetBSD using a "boot disk" command. I googled the problem and bought and installed a replacement TIMEKEEPER chip (M48T08-100). After defaulting the settings and setting the MAC address and machine ID it was happy and booted from disk without intervention. In NetBSD I then set the date and time and all was good. Then I decided to upgrade to the latest version of the SPARC version of NetBSD 9.0. I downloaded and burned the ISO image to CD. Dropped it into a CD caddy and inserted it into the CDROM drive (SUN Model 411 - really a Sony CDU-8012 3.1e). I did a "probe-scsi-all" and it found both the hard drive and the CDROM (target 6 unit 0).