IO Card UARTS 16550 vs 16450??

IO Card UARTS 16550 vs 16450??

Post by Mark Lo » Sat, 07 Jan 1995 04:21:50



..

Quote:>The 16450 has a (practical/usable) maximum speed of 19200,
>whereas the 16550A goes up to 115200.

Not true.  Consider the limit to be 56kbps for the 16450's,
and 115kbps for most 16550A cards.  To actually use a 16450 at 56kbps
in a system with IDE disk drives, you need to use "hdparm -u1 /dev/hda" ...
to avoid dropping characters during disk I/O.  Works great.
--

 
 
 

IO Card UARTS 16550 vs 16450??

Post by Ted San » Sat, 07 Jan 1995 08:13:13


Quote:>Which is better for a LINUX box?  

16550

Quote:>What's the difference?

A 16550 Chip allows for Com Port Speeds above 9600bps.  It has a built in FIFO
buffer and enhances high speed communicaitons greatly.

Quote:>My (cheesy) config is:
>386/sx-16 AMI
>4MB ram, VGA, 100M IDE Drive.

If you ever try to run above 9600 you'll be sorry you bought a 16450.

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IO Card UARTS 16550 vs 16450??

Post by Pete Hoffswe » Sat, 07 Jan 1995 02:04:24


Powersurge took out my multi-io card, and I am about to order another.
Wait, what is this all about!  There are cards with 16550 UARTS and
cheaper ones with 16450.  

Which is better for a LINUX box?  

What's the difference?

My (cheesy) config is:
386/sx-16 AMI
4MB ram, VGA, 100M IDE Drive.
Need:
Multi IO Card, 2s/1p/fd/ide hd or equiv.

I've seen a 16450 2s/1p/1g/fd/hd card for 15 bucks, or
16450 multi io $35
16550 multi io $55
4 16550 serial card ($80) (verynice)

should I go for the 15 dollar cheap-o, or fork over the bucks for the
16550's?

Thanks, Gurus!
 --
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Holland, Michigan    |N9SSA              |http://www.grfn.org/~pete
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IO Card UARTS 16550 vs 16450??

Post by Dan Newcom » Fri, 06 Jan 1995 22:26:27



>Powersurge took out my multi-io card, and I am about to order another.
>Wait, what is this all about!  There are cards with 16550 UARTS and
>cheaper ones with 16450.  
>Which is better for a LINUX box?  

It depends what you do.

Quote:>What's the difference?

100.   :)   Seriously, the SERIAL-HowTo covers this.  The 16550A UART has a 16
byte buffer, whereas the 16450 (and 8450) do not.  This means if communication
gets too fast on the 16450, you lose bytes.  The 16450 has a
(practical/usable) maximum speed of 19200, whereas the 16550A goes up to
115200.

If you have terminals hooked up that can go pretty fast, or anything better
than a 14400 external modem, you'll want the 16550a's.

Quote:>My (cheesy) config is:
>386/sx-16 AMI
>4MB ram, VGA, 100M IDE Drive.
>Need:
>Multi IO Card, 2s/1p/fd/ide hd or equiv.

Also, the 16550A allows you to transfer 16 bytes at a time, instead of just 1.
So that means one interuppt from the CPU instead of 16 for 16 bytes, therefore
increasing performance.

Quote:>I've seen a 16450 2s/1p/1g/fd/hd card for 15 bucks, or
>16450 multi io $35
>16550 multi io $55
>4 16550 serial card ($80) (verynice)
>should I go for the 15 dollar cheap-o, or fork over the bucks for the
>16550's?

Depends.  If you are ever planning on getting a fast modem or anything, go for
it.  If you only use the serial port for mice, I wouldn't worry about it.

        -Dan

--

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"And the man in the mirror has sad eyes."       -Marillion

 
 
 

IO Card UARTS 16550 vs 16450??

Post by Kenneth J. Hendricks » Sat, 07 Jan 1995 12:22:02




>Powersurge took out my multi-io card, and I am about to order another.
>There are cards with 16550 UARTS and cheaper ones with 16450.  

If you ever use a 9600+ bps modem, get a 16550 UART for it.

--
"Arguing about predestination is virtually irresistible."    --RC Sproul

 
 
 

IO Card UARTS 16550 vs 16450??

Post by Andrew R. Tef » Sat, 07 Jan 1995 23:47:51




>...
>>The 16450 has a (practical/usable) maximum speed of 19200,
>>whereas the 16550A goes up to 115200.

>Not true.  Consider the limit to be 56kbps for the 16450's,
>and 115kbps for most 16550A cards.  To actually use a 16450 at 56kbps
>in a system with IDE disk drives, you need to use "hdparm -u1 /dev/hda" ...
>to avoid dropping characters during disk I/O.  Works great.

I second that, although I have never tried to go over 38400; 38400
works great for me too with interrupts unmasked.

--


 
 
 

IO Card UARTS 16550 vs 16450??

Post by Jeffrey D Aspina » Sun, 08 Jan 1995 02:46:08


|> go for the 16550.

|> the 16450 are 1 byte buffer (8 bits),
|> when that buffer is full, an interrupt is generated for the
|> OS (linux in this case) to get that data.
|> at 9600bps that 1200 interrupts/sec
|> on a 386/SX your machine will spend a large portion
|> of the cputime servicing interrupts.
|> a 16550 has a 16 byte buffer( wow! they went all out, sparing
|>                                no expense with memory)

Actually, it has two 16 byte FIFO buffers, on in and one out.

|> and will allow you to use
|> fast devices up to 115000 bps, without bringing your computer
|> to it's knees (or freeze it up).

--

Informatics Core -+- Human Genome Center -+- University of Michigan, Ann Arbor

 
 
 

IO Card UARTS 16550 vs 16450??

Post by sico.. » Sat, 07 Jan 1995 08:31:47



>Powersurge took out my multi-io card, and I am about to order another.
>Wait, what is this all about!  There are cards with 16550 UARTS and
>cheaper ones with 16450.  

>Which is better for a LINUX box?  

>What's the difference?

>My (cheesy) config is:
>386/sx-16 AMI
>4MB ram, VGA, 100M IDE Drive.
>Need:
>Multi IO Card, 2s/1p/fd/ide hd or equiv.

>I've seen a 16450 2s/1p/1g/fd/hd card for 15 bucks, or
>16450 multi io $35
>16550 multi io $55
>4 16550 serial card ($80) (verynice)

>should I go for the 15 dollar cheap-o, or fork over the bucks for the
>16550's?

>Thanks, Gurus!
> --
>-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

>Holland, Michigan    |N9SSA              |http://www.grfn.org/~pete
>-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

go for the 16550.

the 16450 are 1 byte buffer (8 bits),
when that buffer is full, an interrupt is generated for the
OS (linux in this case) to get that data.
at 9600bps that 1200 interrupts/sec
on a 386/SX your machine will spend a large portion
of the cputime servicing interrupts.
a 16550 has a 16 byte buffer( wow! they went all out, sparing
                               no expense with memory)
and will allow you to use
fast devices up to 115000 bps, without bringing your computer
to it's knees (or freeze it up).

 
 
 

IO Card UARTS 16550 vs 16450??

Post by Sean Ber » Wed, 11 Jan 1995 19:32:26




>|> go for the 16550.
>|> the 16450 are 1 byte buffer (8 bits),
>|> when that buffer is full, an interrupt is generated for the
>|> OS (linux in this case) to get that data.
>|> at 9600bps that 1200 interrupts/sec
>|> on a 386/SX your machine will spend a large portion
>|> of the cputime servicing interrupts.
>|> a 16550 has a 16 byte buffer( wow! they went all out, sparing
>|>                                no expense with memory)

It's kind of a trade off.  If you're sending small packets, like keystrokes,
you get better performance with a 16-byte than with a 256 byte buffer, f.e.
If you make the buffer too big, you wait forever for the buffer to fill up.
:)
(MHO, YMMV)
--
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IO Card UARTS 16550 vs 16450??

Post by Andy Burge » Sun, 15 Jan 1995 12:11:07


Quote:>It's kind of a trade off.  If you're sending small packets, like keystrokes,
>you get better performance with a 16-byte than with a 256 byte buffer, f.e.
>If you make the buffer too big, you wait forever for the buffer to fill up.

I think they interrupt after one character time of nothing received
regardless of the number of chars in the buffer.

--
Andy Burgess              A seminar on Time Travel will be held 2 weeks ago


 
 
 

1. Is my modem UART 16450 or UART 16550 ?

I have a Internal 2400/9600 Data/Fax modem. I installed
Linux operating system. The operating system detected my
modem as UART 16450, while the seller (Compaq company) tell
me the modem is UART 16550. I confused.

Should I change the setting to UART 16550 using setserial ?
Any commends ?

Thanks all

Zhiyun Xie
------

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