Not sure what the heck it is. I have changed and upgraded a half dozen times. I have used multiple mothers and I can't recall what is running now.
Probably not SCSI , as that is a very deliberate act, I have a
a PCI SCSI card ( only 160 Mbyte / s transfer rate ) but 3 SCSI Maxtor Atlas 10 K disks for 72 Gigabytes of capacity.
Motherboard is Gigabyte with an AMD64 3000+ processor. kind of overkill for a Browsing system, but very responsive.... I love it.