Building an external SCSI CD duplicator

[Steve]

I've recently acquired all the parts I need to build my own external CD burning tower. A case (or caddy?) with room for four drives, a few Plextor SCSI 40x UltraPlex Max CD-ROMs to choose from, and three Plextor SCSI 40x burners.

The case: eBay

I'm going to connect this machine to my system's LSI 20860, which has an external HD50 connector. The caddy itself has a pair of CN50 connectors on its back. I have a termination plug for the one not connected by the cable. The caddy itself has push-button ID settings on the back, and includes a 200 watt AT power supply.

Basically all I'm asking is whether I'm forgetting or missing anything, and for any insight you can give me into building and using this thing. All advice is appreciated!

 

[fell8]

I'd look int an IDE solution. The drives and cables are cheaperv and easier to find and it doesn't require any accessories. The speed difference is not an issue as the the physical limitations of the media is the limiting factor. There is also a wide selection of drive array options, many of which are fairly cheap themselves.

 

[Peter]

On a SCSI cable, drives can be talked to in parallel. On IDE that's not the case. Four IDE channels going to an external case is hardly practical, or is it?

 

[Steve]

Originally posted by: fell8
I'd look int an IDE solution. The drives and cables are cheaperv and easier to find and it doesn't require any accessories. The speed difference is not an issue as the the physical limitations of the media is the limiting factor. There is also a wide selection of drive array options, many of which are fairly cheap themselves.

I already have all the equipment, except a cable to connect this box to my PC.

 

[Steve]

Peter, while I've got you here let me ask you this: I went with one drive and three burners because of a theory I have (and the burners and full towers are hard as hell to find). The way I figure, let's say all the drives are rotating at 40x (~6MB/s). So would CD-ROM be transmitting to Burner 1 at 6MB/s, Burner 2 at 6MB/s, and Burner 3 at 6MB/s, just under the 20MB/s Ultra SCSI ceiling? Also, wouldn't the 50 Centronics connector be a bottleneck since it does 8-bit and not 16?

 

[Peter]

Sort of yes, although it'll be a tight fit - this works exactly because SCSI has the tricks to decouple interface bandwidth from drive throughput. So if your three Plextors support Ultra interface speed (20 MB/s), you'll be talking to each drive at interface rate. 3x6 MB/s will be a close call though.

On IDE, when you're sending 6 MB/s to a 6 MB/s drive, you're hogging the interface 100 percent of the time, even if it is an UDMA100 interface.