Date: Fri, 20 Oct 1995 05:24:46 -0500 (CDT) From: Joe Greco <jgreco@brasil.moneng.mei.com> To: msmith@atrad.adelaide.edu.au (Michael Smith) Cc: davidg@root.com, root@spiffy.cybernet.com, hackers@freebsd.org Subject: Re: Bragging rights.. Message-ID: <199510201024.FAA29169@brasil.moneng.mei.com> In-Reply-To: <199510200621.PAA17640@genesis.atrad.adelaide.edu.au> from "Michael Smith" at Oct 20, 95 03:51:08 pm
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> > Apparantly, *some* 16550 UARTs will do this, but as far as I know, this > > would be overclocking most versions out there and might result in the part > > overheating (or simply not working at 230K baud). > > The PC16550D (The "reference" part for 16550's) is specified to a 24MHz input > clock. And here I always thought it was the National Semiconductor part that was the "reference" part, because the 16550 was originally their fault. I still have original 16550's around that bear a rather unusual patent marking on them (I can't think of another component where that was done)... anyways, the information I posted and have posted in the past is from NatSemi data books. The NS16550AF is rated at 8 MHz. The NS16C551 is rated at 24 MHz. YMMV depending on the mfr of your particular brand of 16550... however it does look like it is probably safe to at least doubleclock just about any 16550. > The standard clock reference for this part in a PC is 1.8MHz. > Decent serial card vendors (eg. Quatech) offer jumper-selectable clock > dividers to allow you to pick your desired clock rate. I have yet to see this on any reasonably-priced card :-( Fortunately, it's a cheap upgrade to do if you're handy with a soldering iron.. > I would have a hard time believing that a modern CMOS '550 clone wouldn't > handle a 3.6MHz input clock. Yes. ... Joe ------------------------------------------------------------------------------- Joe Greco - Systems Administrator jgreco@ns.sol.net Solaria Public Access UNIX - Milwaukee, WI 414/342-4847
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