[ale] UARTs

[Matt McMillin]

FYI (Fer Y'All's Information),

There are at least a couple of companies that make interface cards with one 
or more serial ports on them that each operate at 230Kbps, rather than 
115Kbps.  The Hayes ESP (Enhanced Serial Port) is probably the best known 
of these, and has been around considerably longer than any of the others I've 
seen since it came out (within the last couple of years).  Last thing I read about 
these cards was that Hayes was having extreme difficulty meeting the demand 
for them.  I don't know how much they usually cost, but knowing Hayes, it's 
probably too much.

Digi International, the makers of DigiBoards, also sells single and double port 
boards that run at 230Kbps.  They, of course, also sell boards with many more 
ports that all run at 230Kbps, but those would be inappropriate for most people 
reading this posting, I imagine.  Unfortunately, I'm not sure what the Digi 
products cost, either.

Finally, I have sitting in front of me a catalog from Global, a mail-order place.  
They have listed a "ultra-speed serial I/O board."  According to the listing, it 
uses not a 16550 UART, but a 16650 UART.  (I suspect that _this_ is the 
fastest one currently available.  What Hayes uses in their design is a 16550 
with a 1M buffer, which is much larger than usual.  And, by the way, it turns 
out that Global sells the ESP, too, at $79.95.)  They're selling the "ultra" board 
for $49.95.  It has one port on it, with a DB-9 connector.  If anyone's interested, 
Global's number is, amazingly enough, 1-800-8GLOBAL.

I have absolutely no idea whether Linux supports any of these boards.  I would 
hope that one could use an arbitrarily high throughput rate with one's serial 
interfaces, but perhaps the Linux kernel must have the supporting code in it to 
do so.  I'd be interested to know what the answer to this question is.

Obviously, perhaps the most appropriate application of one such interface card 
would be to use it with an ISDN terminal adapter (with NT-1), such as the 
Motorola BitSURFR (known to many as the "BitSufferer").  With two 64K 
channels bonded together, the throughput of the line exceeds the 115Kbps 
limit of the standard 16550 UART, so the terminal adapter actually must slow 
to that speed.

INFO WEEK every so often, there are also companies that build serial interface 
cards that have throughputs even _higher_ than 230Kbps, using some sort 
of coprocessor, microcontroller, or customized ASIC chip to handle the flow of 
data.  I hope no one asks me about these boards, as I don't know one damn 
thing more about them than that they exist.

Also, to confirm what someone said about ISDN devices that use Ethernet 
connections instead of a serial port, they do exist.  They're called ISDN routers 
and usually start at over $1000.  Some may not include an NT-1 either, which 
would be an added expense.

Finally, considering the fact that companies such as Media One are going to 
be offering high-speed (probably 10Mbps -- at least unidirectionally) Internet 
access by the end of this year, one might want to give it serious thought 
before they invest at least $200 for an ISDN adapter, perhaps $200 for 
installation of the ISDN line, then $60 a month for ISDN service.  I thought 
about it and decided that getting two more phone lines and 64Kbps service 
for $60 a month wasn't better than paying less than $15 a month for 26400bps 
(on average) on an analog line that I hardly ever use.  (And I would have still 
bought my modem, just in case I wanted to dial a BBS.)

-M