Booting sequence issue with T5500

I have 2 T5500 (RAID & Non RAID). Specifications are as given below:

 Bios – A01

CPU – E5506 2.13GHz / X5570 2.93GHz

Memory – 3GB (3*1GB DDR3)

Video – Nvidia Quadro FX580 / NVS 420

ODD – Internal -- PLDS DVD+/- RW DH-16A6S / External -- Sony Optiarc AD 7240S

 I have intended to implement following BIOS settings:

1) System Configuration à  USB Controller à No Boot.

2) General à Boot Sequence à

·         Onboard or USB floppy drive

·         Onboard or USB CDROM drive

·         HDD( WDC WD1600AAJS)

I have saved settings and exit from the BIOS. I have inserted the Bootable CD on CDROM (OS CD) and were trying to boot the machine from the CDROM.

 but the System can not boot from the CDROM. It shows “No boot device available”.

 After that I did following changes to BIOS settings:

1) System Configuration à  USB Controller à Enable.

No changes made to boot sequence. Now if I boot the machine using the same bootable CD as above and this time boot from CDROM was successful.

 Queries:

1. Is this a known issue?

2. Why this malfunction is happening?

3. In BIOS how this USB Controller option play with boot sequence?

Regards

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B.Akbar