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Conference wrksys::alphastation

Title:	Alpha Workstation Conference
Notice:	See note 1.* for conference notices
Moderator:	WRKSYS::HOUSE

Created:	Wed Sep 07 1994
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	1996
Total number of notes:	9122

1896.0. "External devices for AlphaStation 255?" by HGOVC::PATRICKNG () Mon Mar 17 1997 09:37

    Hi,
    
    Is it possible to connect external CD-ROM and TLZ09 on the external SCSI 
    port at the back of an AlphaStation 255/233?
    
    
    AlphaStation 255/233 (ext SCSI port) --BN21H-1E(1.5m)--connect to--
    (RRD45-VA+TLZ09_VA) in BA356-KD with BA35X-MG
    
    Does it works?
    
    I believe the external SCSI port is used to connect external SCSI
    devices. What are the limitation?
    
    
    Thanks,
    Patrick

T.R Title User Personal
Name Date Lines

1896.1 bus is too long for fast operation WRKSYS::HOUSE Kenny House, Workstations Engineering Mon Mar 17 1997 11:10 23

T.R	Title	User	Personal Name	Date	Lines
1896.1	bus is too long for fast operation	WRKSYS::HOUSE	Kenny House, Workstations Engineering	`Mon Mar 17 1997 11:10`	23
	The rule for fast SCSI operation is that the total bus length has to be three meters or less. I'm not entirely sure of some of the numbers, but your proposed bus looks like 0.9 BA356 internals 1.5 cable 1.2 AlphaStation 255 internals (could be more or less) --- 3.6 total If you're running OpenVMS, you can set the SCSI bus to run in "slow" mode with the Console command "set pka0_fast 0" (I think); that'll get you to a comfortable four meters total bus length (yes, I know what ANSI says, but stick with four meters and you'll be happier). Digital UNIX may still require a rebuild of the kernel to run slow. Windows NT may not have a way to slow down the bus. Another tactic is to add a KZPAA PCI-SCSI host adapter for the external devices. That way, you keep your internal devices running faster. -- Kenny House

    The rule for fast SCSI operation is that the total bus length has to be
    three meters or less.  I'm not entirely sure of some of the numbers,
    but your proposed bus looks like
    
    	0.9	BA356 internals
    	1.5	cable
    	1.2	AlphaStation 255 internals (could be more or less)
    	---
    	3.6	total
    
    If you're running OpenVMS, you can set the SCSI bus to run in "slow"
    mode with the Console command "set pka0_fast 0" (I think);  that'll get
    you to a comfortable four meters total bus length (yes, I know what
    ANSI says, but stick with four meters and you'll be happier).
    
    Digital UNIX may still require a rebuild of the kernel to run slow.
    
    Windows NT may not have a way to slow down the bus.
    
    Another tactic is to add a KZPAA PCI-SCSI host adapter for the external
    devices.  That way, you keep your internal devices running faster.
    
    -- Kenny House