AKONSTAM@TRINITY.BITNET (AARON KONSTAM) (09/13/90)
I have a question about disk connections to theSCSI bus in a 3/160, and I assume other Suns with towers. Our 3/160 has two Micropolis 1355 internal disks in its tower together with an Emulex controller to control them. We also have a WREN VI drive in a shoebox connected directly to the SCSI board in the tower with a ribbon cable. According to the block diagrams that I have seen for the 3/160 the SCSI board should be connected to the VME bus (and it is through three edge connectors) and the Emulex controller in the tower should be connected between the SCSI board and the disk drives. I can find no conections on the SCSI bus except the edge connectors to the VME bus and the ribbon cable to the shoebox. How are the the Micropolis 1355 which are supposed to be SCSI disk drives getting control signals from the SCSI bus? I will have to admit the machine works with out my understanding this but if someone could clear up this mystery I would appreciate it. AARON KONSTAM Trinity University 715 Stadium Dr. SAN ANTONIO, TX 78212 (512)-736-7484 AKONSTAM@TRINITY.BITNET
cjp%megatek.UUCP@ucsd.edu (Christopher J. Pikus) (10/08/90)
From article <1990Sep12.175832.11438@rice.edu>, by AKONSTAM@TRINITY.BITNET (AARON KONSTAM): > I have a question about disk connections to theSCSI bus in a 3/160, and I > assume other Suns with towers. Our 3/160 has two Micropolis 1355 internal > disks in its tower together with an Emulex controller to control them. We > also have a WREN VI drive in a shoebox connected directly to the SCSI > board in the tower with a ribbon cable. > > According to the block diagrams that I have seen for the 3/160 the SCSI > board should be connected to the VME bus (and it is through three edge > connectors) and the Emulex controller in the tower should be connected > between the SCSI board and the disk drives. I can find no conections on > the SCSI bus except the edge connectors to the VME bus and the ribbon > cable to the shoebox. > > How are the the Micropolis 1355 which are supposed to be SCSI disk drives > getting control signals from the SCSI bus? I will have to admit the > machine works with out my understanding this but if someone could clear up > this mystery I would appreciate it. > This is a very common question asked in this group. (perhaps someone should collect all these answers and post them monthly. :-) The SCSI cable connection to the "VME bus" is not really directly to the bus. On slot 7 of the sun motherboard, the "P2" connector on the back has the extended pins for a connector. In the VME spec, the outer 2 rows of the P2 conector is left for OEM defined functions. On the Sun they are left unconnected on slots 7, 8, and 9. If you look in your 3/160 card cage, you will see a card in slot 7. THis is the SCSI controller. It outputs its SCSI control signals on the outer 2 rows of the P2 connector which go to the Emulex ESDI bridge controller (and the external shoebos). To prove this hypothesis, move the SCSI controller from slot 7 to another slot and watch it not work. :-) Be Seeing You ... Christopher J. Pikus, Megatek Corp. INTERNET: cjp@megatek.uucp San Diego, CA UUCP: ...!uunet!megatek!cjp
jms@tardis.tymnet.com (Joe Smith) (10/08/90)
In article <1990Sep12.175832.11438@rice.edu> AKONSTAM@TRINITY.BITNET (AARON KONSTAM) writes: >X-Sun-Spots-Digest: Volume 9, Issue 312, message 1 > Our 3/160 has two Micropolis 1355 internal >disks in its tower together with an Emulex controller to control them. We >also have a WREN VI drive in a shoebox connected directly to the SCSI >board in the tower with a ribbon cable. >How are the the Micropolis 1355 which are supposed to be SCSI disk drives >getting control signals from the SCSI bus? They don't. The Micropolis is an ESDI disk, not a SCSI disk. The CPU talks to the SCSI host adapter via the VME bus. The SCSI bus goes from the host adapter, to the Emulex card, and to the embedded SCSI controller in the WREN. The Emulex MD21 disk controller translates the SCSI commands the ESDI commands that the Micropolis disks understand. The MD21 reports to the SCSI bus that it is a single SCSI controller with 2 logical units. The WREN disk has a SCSI controller bolted to the disk; it is set up as a controller with a single logical unit. (If you have an Adaptec ACB-4000 controller, it allows ST-506 disk to be connected to the SCSI bus.) Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com BT Tymnet Tech Services | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-C41 | BIX: smithjoe | 12 PDP-10s still running! "POPJ P," San Jose, CA 95161-9019 | humorous dislaimer: "My Amiga speaks for me."