"PIC" vs "APIC" setting in BIOS

Hi All,

I believe "PIC" allows for the standard 16 IRQ's, while "APIC" allows for more (unlimited?). My BIOS is set for APIC and everything works great in XP - EXCEPT - my old Adaptec 2940W SCSI card will no longer "rescan" the bus correctly. This means I need to turn on the scanner and reboot for detection if it's not altready turned on.

So!

Today I tried resetting my BIOS to "PIC ", but XP would never boot. in fact, I never even got the logon pic! I guess, what I'm looking for, is anyone running in PIC mode? I'm sure there are older systems out there that do not have a choice, so how are they configured?

The point to this exercise in futility was to see if perhaps the old Adaptec card would respond to a rescan if it was on a lower (recognizable) IRQ. It's currently on IRQ 22!

TIA!

Russ

 

You can limit XP to the original 16 IRQ's, providing you don't have devices that take up more than that.
Disable com 1 and 2 in BIOS, to free up two more for PCI devices, and you should be OK.
If you wish to get XP to run that way, you'll have to do a clean install. You cannot simply expect all IRQ's to magically change to one within the 16 limit, when you restart the computer.

 

I'm not suprised! Thanks for the info. Any input on why doing a "rescan bus" on my SCSI card no longer works under XP when it worked fine under '98SE? By that, I mean "scan for hardware changes" in device manager, and "rescan SCSI Bus" using a SCSI tool to reset the bus - both used to work, neither work now.

Russ

 

There's probably ghost devices on the scsi bus, and Windows thinks all is well, thus you can rescan and nothing changes.
In Safe Mode, go into device mangler, remove your scsi devices, and restart. Everything should reinstall for only the devices that are actually present.