CompuServe Messages

I'd like to try and hopefully straighten out a few misconceptions about SCSI. First there was just "SCSI" (1 or I if you like). This was a command set and an 8 bit interface. "SCSI-II" (2) is an expanded command set, but is still based on the 8 bit interface. "SCSI-II WIDE" is the SCSI-II protocol using a 16 bit interface, allowing up to twice the maximum data transfer rates of 8 bit SCSI (I or II). "SCSI-II FAST" can be implemented on either the 8 or 16 bit interface, and means that it supports synchronous (burst) transfers of 10 million 8 or 16 bit transfers per second instead of the normal 5 million. Most original SCSI controllers were SCSI-I command compatible, using 8 bit interfaces. GVP's Series II HC8 board which has been around for a few years supports the SCSI-II command set, and is 8 bits wide. This means in theory it could support up to 5MBytes / second, but it doesn't due to various hardware limitations in it. It's actual limit is about 3.5MB/second, I believe, although I could be a bit off on that figure. Commodore's latest and greatest 4091 is a SCSI-II FAST 8 bit interface card I believe, meaning that it that supports bursts up to 10MB/second. If such a beast existed for the Amiga, a SCSI-II FAST *and* wide interface card could support up to 20MB/second. BUT, before you drool over these big numbers, you need to look at the reality of what typical drives can ACTUALLY deliver. We at GVP look at drives all the time, and even the most blazingly fast drives certainly cannot out perform the 4091 AND MORE IMPORTANTLY, *most* drives cannot out perform even our lowly HC8 (the Rodney Dangerfield of controllers it seems these days). So, my advice – before you decide you MUST have the fastest controller there is, you should first decide if you're ever likely to shell out the money for the type of drive that can use it. You might just be able to save yourself a bunch of money by buying a simple HC8 and put the money you'll save toward some software perhaps or even a bigger drive. I hope this helps… Regards, Paul.