Newsgroups: comp.sys.dec.micro From: wampler at microunity dot com (Kurt Wampler) Subject: Re: Dec PRo help Nntp-Posting-Host: thoas.microunity.com Organization: MicroUnity Systems Engineering Inc. Date: Sat, 17 Apr 1993 22:00:33 GMT dsc at zebedee dot swindon dot gpsemi dot com (Dave Clarke x8048) writes: >hi, > I want to add a further RX50 drive to my PRO350 to get DZ3:,DZ4:. >But, I have a problem that I cannot make the drive online to the PO/S >V3.2 operating system. I have tried the J17 drive select plug in both drives >(DZ1:,DZ2:, one pair and DZ3:,DZ4: the other); But each time the drive acting >as DZ1/2 works and DZ3/4 do not become online. Does anyone out there know >what I have to change or set to make these drives online. Further to this I >will be wanting to add another hard disk to a PRO380, and think that I will >have the same problem as the RX50's. > > PLEASE HELP, > many thanks, > Dave. Dave - I dug out my PRO300 Technical Manual and studied it a little in an attempt to answer your question. The documentation is inconsistent. On p.10-36 there's a table that purports to describe how the select pins affect the drive. It states: DRIVE SEL3 L Selects drive side B if J17 installed DRIVE SEL0 L Selects drive side A if J17 not installed DRIVE SEL1 L Selects drive side B if J17 not installed DRIVE SEL2 L Selects drive side A if J17 installed I'm not sure what this means, since the RX50 drive records one side only of each diskette, and only has a read/write head on that side of the diskette. The chapter on the RX50 controller adds to the confusion. Section 9.3.3.2 on p.9-14 states: "The microprocessor generates four signals for selecting an RX50 drive: UNIT 0, DRIVE 0 and SEL EN, and SIDE. The SIDE signal is reserved for future use. A unit selection decoder decodes the remaining signals and generates the drive select signals, SEL0 L, SEL1 L, SEL2 L, or SEL3 L. Table 9-4 shows this conversion." Table 9-4 Drive Select Signal Conversion Asserted Control Signals Asserted Selects UNIT0 H DRIVE0 H SEL EN L 0 1 2 3 X X No No No No No No No Yes No No No Yes Yes No Yes No No Yes No No Yes Yes No Yes No No Yes Yes Yes Yes No No No It seems like there was some confusion among the designers about the exact definitions of "drive" "unit" and "side". It's as though there was a debate about whether to use the signals to select 4 different diskettes (A,B,C,D) or to at some later time support double-sided diskettes. Also, the chapter on the RX50 controller states on p.9-2: "The controller interfaces *one* RX50 dual diskette drive to the host processor [to] provide 819,200 bytes of storage." Maybe my book's out-of-date and they cleaned up these inconsistencies in a later version... P/OS 3.2, however, does have those device definitions for DZ1, DZ2, DZ3, and DZ4, implying that they did support a dual-RX50 configuration. I wonder what would happen if you just installed J17 on a single RX50 unit and booted up P/OS. Would it show up as DZ3/DZ4 online? Conclusion: the documentation I have is not sufficient to answer your question. But perhaps the above information is of use. Good luck! Kurt Wampler wampler at MicroUnity dot com