Path: utzoo!attcan!uunet!cs.utexas.edu!usc!apple!AppleLink.Apple.COM!Smyers.S
From: Smyers.S@AppleLink.Apple.COM (Scott Smyers)
Newsgroups: comp.periphs.scsi
Subject: Re: NEC CDR-35 portable CDROM drive
Message-ID: <8575@goofy.Apple.COM>
Date: 6 Jun 90 18:36:03 GMT
References: <12215@shlump.nac.dec.com>
Sender: usenet@Apple.COM
Organization: Apple Computer
Lines: 33

In article <12215@shlump.nac.dec.com> mattioli@took.enet.dec.com (John R. 
Mattioli) writes:
> I don't see why I should have two SCSI busses in my systems.
> 
>         If anyone could shed some light on this problem, please respond 
via mail
> or reply here.  The CDROM technology is so great it would be a sin to 
cripple it
> by forcing it to be attached to a nonstandard SCSI controller.

There's nothing "standard" about SCSI controllers in the PC world.  The 
only thing that's standard is the SCSI bus which goes to the outside 
world, but as far as DMA, interrupts, control registers, on board RAM and 
everything else, each SCSI controller has its own way of doing things.  
This is not a problem which is unique to CDROM drives - try buying another 
HD from a different vender, or a scanner, or a SCSI printer, or a tape - 
they're all going to try to sell you yet another SCSI controller, even 
though they could all play on the same bus, if someone took the time to 
write device drivers for each device for your one SCSI controller.  The 
problem is that venders don't know what SCSI controllers their customers 
have, and SCSI controllers are relatively easy to design, so everybody 
makes their own, then writes a device driver for their device which only 
works with that SCSI controller.

Hopefully this state of affairs will improve in the future.  The SCSI CAM 
committee has formed to address this exact issue.  I was a member of that 
committee for about the first 10 meetings and at every meeting someone 
brings up a problem exactly like you're describing - "I already have a 
SCSI bus on my PC - why can't I buy brand X SCSI device and plug it in?"  
God and ANSI willing, some day, you will.

------------------------------
The ideas presented here are my own, not Apple's.