AST 4 PORT card information

Mapping the SW's to the functions:

SW1-1 : IRQ2   SW2-1 : IRQ5   SW3-1 : XA1
SW1-2 : IRQ3   SW2-2 : IRQ6   SW3-2 : XA0
SW1-3 : IRQ4   SW2-3 : IRQ7   SW3-3 : INT
                              SW3-4 : SHR
XA0 (SW3-2) Address range
OFF : 1A0h (1B0h) - 1BFh
ON  : 2A0h (1B0h) - 1BFh
XA1 (SW3-1) Operation mode port J1 & J2
OFF : 4port mode
ON  : COM1 & COM2
INT (SW3-3) Interrupt enable
OFF : interrupt disable
ON  : interrupt enable
SHR (SW3-4) Share interrupt with other 4port
OFF : Single 4 port card
ON  : Two 4 port cards

The INT switches are trival. Just put one IRQ, a free one, ON.


Some DOS software I found somewhere on an AST ftp server a long time ago (I forgot where).
ASTCOM2.ZIP A driver
CC832TST.ZIP A test program
FOURPORT.ZIP Source code examples.
Cable wiring.

Don't forget to dedicate the IRQ to ISA in the BIOS configuration setup. Sharing it with a PCI card does not result in an error message (with Linux), but it works really slow (1 character in ten seconds or so).

A long time ago I asked for the info presented above in comp.os.linux.hardware, and got the following replies:
(I scanned it much later, so beware for OCR errors)

Date: Wed, 17 Jul 96 19:53 EDT
From: (Dave Bullis)
To: fjkr@gatekeep (Fred Jan Kraan)
Subject: Re: AST Fourport dipsetting info needed
Newsgroups: comp.os.linux.hardware
Organization: Sillub Technology
X-Newsreader: TIN [version 1.2 PL2]
Status: RO
X-Status: D

In article  you wrote:
: This is what I found out:

: XAO XA1  addr
: OFF OFF  1AOh-1BFh
: ON  OFF  2AOh-2BFh
: OFF ON   1BOh-1BFh
: ON  ON   ??

: Setting the card to address 1AOh-lBFh, interrupt 2 and SHR ON,
: and enable the card with /etc/rc/d/rc.serial
: seems to work but sends characters to the port at a rate of
: approximately one character in ten seconds (19200 baud), so
: something must be wrong.

: Thanks a greetings,

Fred Jan Kraan

Do you have SW3-3 (INT) ON?
And do are setting irq 9 with setserial?

/etc/setserial -v /dev/ttyS4 uart 16450 port OxlAO irq 9
/etc/setserial -v /dev/ttyS5 uart 16450 port OxlA8 irq 9
/etc/setserial -v /dev/ttyS6 uart 16450 port OxlBO irq 9
/etc/setserial -v /dev/ttyS7 uart 16450 port OxlB8 irq 9

Worked for me before I switched motherhoards had lost a slot for it.

Dave Bullis

Dave Bullis      
Sillub Technology	
Date: Wed, 17 Jul 1996 15:11:42 +1000
From: leon garde 
Message-Zd: <>
To: fjkr@gatekeep
Subject: Re: AST Fourport dipsetting info needed
Newsgroups: comp.os.linux.hardware
Content-Type: text
Status: RO

In comp.os.linux.hardware you write:

>Some time ago I bought a AST Fourpart card in a DEC repacking.
>Alas the manual was replaced by quite useless DEC installation

>Now I cannot find the right dip-switch settings to configure
>the card for Linux. Can someone send me an installation
>abstract or a pointer to the manual?

>This is the information for the card:

>AST CC-832

>Dip switches:

>  2    3    4    5    6    7   XA1 XAO INT SHR
>|             ||             ||               |
>|             ||             ||               |
>|             ||             ||               |

>This is what I found out:

>XAO XA1  addr
>ON  OFF  2AOh-2BFh
>OFF ON   1BOh-1BFh
>ON  ON   ???
ON  ON   2BOh-2BFh . well, i have a recollection of it being so simple :)
>Setting the card to address 1AOh-lBFh, interrupt 2 and SHR ON,
>and enable the card with /etc/rc/d/rc.serial
>seems to work but sends characters to the port at a rate of
>approximately one character in ten seconds (19200 baud), so
>something must be wrong.

turn SHR off. it is for compatibility mode
INT is on, it is enable interrupt.

but if that doesnt work, change the settings again.
there are only 4 different settings to try :)


Date: Tue, 16 Jul 1996 20:56:31 +0100 (BST)
From: Bill Hay 
To: fjkr@gatekeep
Subject: Re: AST Fourport (fwd)
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Status: RO

"You know what really burns my ass?"  Tinya Wazzo Bill Hay

---------- Forwarded message ----------
Date: Mon, 3 Jul 1995 23:40:03 -0500
From: Stephen Denny 
Newgroups: comp.os.linux.hardware
Subject: Re: AST Fourport

In article  you write:
>I've just acquired 2 AST Fourports.  Each has 4 chips marked 16C450.  These
>look to be fairly easy to remove but can they be upgraded to 16550s?
>There are three switch blocks on each card   The first two are obviously for
>selecting the IRQ used.  The third has four switches marked XA1, XAO, INT
>and SHR.  Any idea what these do ?

I am using Fourports here with linux with excellent results.  Yes,
immediately replace the 15450s to 16550A versions.  If you need a cheap
source I can pass mine along.  I buy them 20 at a time.

Since I buy my Fourports new, I have complete (HA) documentation sets.
I'll try to summarize the switches below, but if you have further questions
let me know.

A summary first (this is how I set mine).

IRQ2  up (obviously I use this)
IRQ3  dn
IRQ4  dn

IRQ5  dn
IRQ6  dn
IRQ7  dn

compatible mode	         dn
high addr range	         dn [2AO]
IRQ sharing off	         up
reserved - set off only  dn

from the manual:

IRQx: Enable only one interrupt request (IRQ) line.
If there are two Async Cluster Adapters [fourports]
in your system, configure both for the same IRQ.

compatible mode: You might configure your first Async Cluster
Adapter [fourport) board for compatible mode if your PC-AT has a
second operating system that requires COM1 and COM2.
Also known as Enhanced mode, the second (fourport) must be
in enhanced mode.
[Basically if you want to use two other serial ports prior to
the fourport use this to make the fourport skip them.]
high addr range [I/0 Address): First board: high address range
(SW3-2 ON).  Second board: low address range (SN3-2 OFF).
In enhanced mode, the high address range is 02A0-02BFh, and the
low address range is 01A0-01BFh.

interrupt sharing: Enabled: (SW3-3 OFF).  This setting allows two
fourports in the same

Latest update: 2004-05-22