From: davidg@aegis.or.jp (Dave McLane)
Newsgroups: comp.dcom.modems
Subject: Re: Can I upgrade a 16450 uart to a 16550a?
Date: 10 Jan 93 01:11:45 GMT

jim@n5ial.mythical.com (Jim Graham) writes:

>In article <1993Jan7.152939.28987@wam.umd.edu> joel@wam.umd.edu writes:

>> I was almost sure Dell would have put a good uart in the
>> machine, but it turns out it's only a 16450.

How do you know it's a 16450? I have a Dell 325D (which is what I
believe you are referring to) and MSD (MicroSoftDiagnostics) says it
has 8250 UARTS. 

>well, they did put a ``good'' UART in the machine....  they just didn't
>put the *BEST* UART in.  I've yet to see a serial board that comes with
>a 16550A or 16550AF already installed.  (I would love to see this change,
>of course!)

Me either. That's the trouble with the small footprint design; they
tend to have things built-in so you either have to get a new one or
add a card. 

>> Naturally, I'm losing
>> char.s with high-speed transfers, especially with a loaded machine
>> (I'm running Linux --- a Unix clone).
>
>first, check your flow control setup.  make sure you've got fully
>bi-directional (RTS/CTS --- more correctly referred to as RFR/CTS) flow
>control setup in both the software and the modem.  if you don't have
>good flow control in operation, you're could easily lose characters no
>matter what UART you've got.

If he's talking about the Dell 325D, I have one and it does indeed
drop characters at speeds faster than 9,600/19,200. 

>also, when you upgrade, make sure that the software does support the
>16550 fully --- if not, you've just replaced a 16450 with what will be
>treated as a fast 16450....

Right. The first board I was only recognized as that, a 16450.  It
doesn't really matter what somebody says it is, but what the
software recognizes it has. In addition to MSD (above) I used a
utility that came with the X00 driver to verify that the ports were
being recognized as 16550AFN. And if you're running FAS with UNIX,
it tells what kind of chips you have on boot. 

>> Is it possible to upgrade the 16450 to a 16550a?

>yes.  they are pin-compatible, provided that you replace it with the
>same package...e.g., replace DIP (16550AN or 16550AFN) with DIP, etc.
                                        ^           ^
But in the case of the Dell 325D, the "16450" isn't a separate chip;
it's part of VLSI which is soldered in place. In such cases you have
to add a card with the new chips on it.

>> (I assume that will
>> help the problem; correct me if I'm wrong.)  
>
>see above --- it's part of what will help, but there are other things to
>look at as well.

>> [I tried asking the representative a Dell, but, when he answer my
>> question of "What kind of uart is in the machine" with "You have a
>> VLSI chip," I gave up.]
>
>usually (and there are exceptions), sales droids don't have a clue about
>these things.  the guy you talked to probably doesn't know the
>difference between a UART and a toaster, and just pulled out a term
>(VLSI) that he'd heard in the past somewhere.  :-)

Sorry, but the ignorance is on your side. The Dell 325D does in fact
have a VLSI. I would say the trouble with the person at Dell was they
assumed you were computer literate :-)

In the "Dell System 325D and Dell System 333D User's Guide", they
are referred to as "INTEGRATED DEVICES" (p 2-10, full caps in the
original), and "built-in" (p. 3-6). It also talks about the
autoconfiguation capability for the serial ports which "lets you add
an expansion card containing a seriall part that has the same
designation as one of the built-in ports without having to
reconfigure the card" (p 3-7). 

>e-mail me if you want more info, have questions, etc.
>   --jim

Better yet, RTM :-)

Dave

--
Dave McLane 
JUNET: davidg@aegis.or.jp (ONLY within Japan: post otherwise)
Nagaokakyoshi, Kyoto Japan Tel: +81-75-951-1168 Fax: +81-75-957-1087

Newsgroups: comp.dcom.modems