Posting this for the benefit of other ppl who might run up to the same problem.
It appears that the reason my DVD ROM drive was not recognized by my M6H was the fact that:
1. Either the IDE TO SATA card was not seated properly.
2. Or that the DVD ROM power cable was not seated properly.
I solved the issue by reseating both the power cable on the DVD ROM drive as well as reseating the IDE TO SATA convertor card.
For the record, DVD ROM drive used is:
LG MODEL GDR-H30N (MANUFACTURED JULY 2007) DVD ROM DRIVE, a relic from my first Intel Core 2 Extreme
QX9650 on a Gigabyte P35 DS4 motherboard build back in March 2008.
https://www.lg.com/us/commercial/documents/gdr-h30n-spec-sheet.pdfNow that the IDE TO SATA Convertor Card is seated properly, the boot time is back to normal, which is around 5 seconds
on my i7-4770K@4.42 GHz/Maximus VI Hero.
Hope this post helps people.
God bless.