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1998-05-02
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7mCommodore A4091 SCSI Host Adaptor 0m
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Commodore A4091 SCSI Adaptor
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This page was added specifically because so many people appear not to
actually have any documentation on the 4091. I know, because I'm the one
who had to answer all the queries in #amiga on IRC :) The 4091 was licensed
to DKB who built it for a while as well. This documentation refers
specifically to the Commodore version as I'm not sure what changes DKB made
to the design (if any.)
I'm trying not to break any copyright with Commodore's original
documentation, but I do need to try to get the information across, so give
me some leeway if I stray :)
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7mAvailable topics are: 0m
7mFeatures 0m
7mDipswitch Settings 0m
7mPin Outs 0m
7mFirmware Revisions 0m
7mGeneral Questions 0m
7mTrouble shooting 0m
7mWho Designed it? 0m
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7mFeatures 0m
Full Zorro III support
SCSI-2 support
Internal 50 pin SCSI connection
External High density SCSI Connector (aka Mini-D 50)
Direct Memory Access (DMA) for fast transfers
Mounting support for 3.5" harddrive on the card
7mDipswitch Settings 0m
Board's SCSI Address (Switches 1,2,3)
ID 0 -- 1 ON ; 2 ON ; 3 ON
ID 1 -- 1 OFF; 2 ON ; 3 ON
ID 2 -- 1 ON ; 2 OFF; 3 ON
ID 3 -- 1 OFF; 2 OFF; 3 ON
ID 4 -- 1 ON ; 2 ON ; 3 OFF
ID 5 -- 1 OFF; 2 ON ; 3 OFF
ID 6 -- 1 ON ; 2 OFF; 3 OFF
ID 7 -- 1 OFF; 2 OFF; 3 OFF (Default)
SCSI Fast Bus (Switch 4)
OFF = SCSI Fast Bus enabled.
ON = SCSI Fast Bus disabled. Set this if none of the devices on the SCSI
chain support SCSI Fast Bus.
Short/Long Spinup (Switch 5)
OFF = System uses standard spinup booting time
ON = System uses longer booting period. Set this if one of the SCSI devices
is not recognised under a shorter booting period.
Syncronous Mode (Switch 6)
OFF = Mode is enabled. This means that not evey byte sent over the SCSI bus
is acknowledged leading to improved response times.
ON = Mode is disabled.
External Termination (Switch 7)
OFF = Termination is turned ON. This means you do not have any external
SCSI devices.
ON = Termination off. This means you do have external devices and the last
one must be terminated.
Logical Unit (LUN) Enable (Switch 8)
OFF = Unit 0 is the only unit recognised.
ON = Units 1-6 are now recognised. This is essential is you have a multiple
unit device in your SCSI bus such as a CD-ROM jukebox. Otherwise only the
first CD will be recognised.
7mPin outs 0m
1 Ground 26 /DB(0)
2 Ground 27 /DB(1)
3 Ground 28 /DB(2)
4 Ground 29 /DB(3)
5 Ground 30 /DB(4)
6 Ground 31 /DB(5)
7 Ground 32 /DB(6)
8 Ground 33 /DB(7)
9 Ground 34 /DB(P)
10 Ground 35 Ground
11 Ground 36 Ground
12 Reserved 37 Reserved
13 Open 38 TERMPWR
14 Reserved 39 Reserved
15 Ground 40 Ground
16 Ground 41 /ATN
17 Ground 42 Ground
18 Ground 43 /BSY
19 Ground 44 /ACK
20 Ground 45 /RST
21 Ground 46 /MSG
22 Ground 47 /SEL
23 Ground 48 /C/D
24 Ground 49 /REQ
25 Ground 50 /I/O
7mFirmware Revisions 0m The most recent ROM is 40.13. Thanks to 7mPaul Reeves 0m of 7m
Asimware Innovations 0m for that.
7mGeneral Questions 0m
What's the device name for the 4091?
2nd.scsi.device -- Make sure you type it exactly.
Why isn't it in DEVS:?
It's ROM based. This means that the machine can boot off a drive installed
on the 4091. If it was a disk file, you'd have to load it from disk first.
But since you don't have a harddisk since the 4091 isn't recognised yet,
you'd have to boot from floppy (or the internal IDE drive...if you still
have one!)
Which way in does the external connector go?
Sensibly enough, there's only one way it will fit physically, and that's
the correct way. But for those who really want to know, looking from the
back on the 4000, pin 1 is on the top left corner where the housing is
widest. Pin 25 is on the top right, pin 26 in on the bottom left, and pin
50 is on the bottom right.
7mTroubleshooting 0m
System has a nasty habit of hanging on disk accesses.
You've not terminated the bus correctly. Check to see if you have used
either the internal terminator supplied with the 4091 or that the last
internal device has its own termination set. Then check the external
termination.
Check your cabling. Bad cabling causes more SCSI problems than just about
any other cause and it's a pain to track down until you realise that.
Ensure that you don't have any SCSI ID conflicts.
You have more than one Zorro 3 DMA device (such as a Cybervision 64). If
possible, put that other device into a slow mode.
The 4091 doesn't like my machine.
You are using an Amiga 4000 aren't you? Using the 4091 with the 3000 is
possible, but not recommended.
Make sure you have the Rev 11 Buster chip (if you're facing the 4000 from
the front, it's to the left of the slots about half way to the back of the
machine. The suffix should be -11. If it isn't, try to find a replacement
from one of the parts companies.
7mDesigners 0m Data not available. I've not opened up the 4000 recently to look
at the names on the PCB :)
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This page was last updated on the 20th of June.
For comments, corrections and additions, please send email to 7m
adamh@spots.ab.ca 0m