Is this what I need? Adaptec AHA-2940UW
It's the UW model and it stands for Ultra Wide. What does it mean?
You should be able to use that. I've got one of those, and it's got both the regular Fast SCSI-2 50-pin connector, and the higher bandwidth "Wide" 68-pin connector. The "Ultra" is just the name of the faster SCSI standard.
WinXP : PIII 1.4GHz, 512MB RAM, 73GB SCSI HDD, Matrox Parhelia, SB Audigy 2.
Win98se : K6-3+ 500MHz, 256MB RAM, 80GB HDD, Matrox Millennium G400 MAX, Voodoo 2, SW1000XG.
DOS6.22 : Intel DX4, 64MB RAM, 1.6GB HDD, Diamond Stealth64 DRAM, GUS 1MB, SB16.