I too have buildt one. My A500+ has an internal zorroII scsi-card with 2MB fastRam and HD. I did not use any extra chip tough I remember it was recommended, I followed some instructions on Aminet, and It worked right away. It slowed down the computer abit tough, and if I query the scsi-device the whole thing hangs. The GVP software works ok, however. Maybe the missing logical chip would correct that, not sure what it is for.