ISA is 8MHz*16-bit=128Mb/s=16MB/s. As you can see, the max data flow is 16MB/s, which only meets original Fast SCSI standards (10MB/s). While this is fine for a CD burner (1x=150KB/s, so 68x=10MB/s), it's far too slow for reasonable hard drive performance.
What's the frequency, Kenneth?