That useless A590 switch 4!

[Zac67]

1. deactivate LUN support (sw 2 off) - most probably LUNs work anyway, just not for booting from or auto-mounting
2. put your boot drive on ID 0 or 1 and use HDToolbox to mark it as last drive
3. deactivate long spin-up time (sw 3 off) - if your drive doesn't work without it better replace it anyway

This should start booting within 2 or 3 seconds.

[Zac67]

HDToolBox worked great for me with mine.  If you disable the LUN support, won't you also lose the option to use multiple cards (think it will limit you to just the CF in the PCMCIA slot)?

As long as you're using mountlists to mount the other cards I don't think it matters. The LUN scan should only affect the automount and autoboot mechanism; when a mountlist entry is used the controller should be looking at that LUN anyway. I'm not 100% sure (ignoring LUNs just because the scan is deactivated would be braindead though) but it doesn't hurt to try.
Back when I had an A590 I did a lot of hot-plugging and such, so what's been scanned during boot shouldn't really matter.