Path: utzoo!attcan!uunet!husc6!think!ames!pasteur!ucbvax!decwrl!decvax!tektronix!reed!omen!caf
From: caf@omen.UUCP (Chuck Forsberg WA7KGX)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Faster Serial Ports... How can I?
Message-ID: <691@omen.UUCP>
Date: 12 Jun 88 09:51:55 GMT
References: <302@grinch.grinch.UUCP> <16800296@clio>
Reply-To: caf@omen.UUCP (Chuck Forsberg WA7KGX)
Organization: Omen Technology Inc, Portland Oregon
Lines: 26

The maximum speed without dropping characters depends on many factors.
Terminal emulators differ in their speed, especially when scrolling or
decoding and executing escape sequences.  Pro-YAM and its shareware
cousin ZCOMM are among the fastest and most accurate in VT10x emulation.

The actual max speed also depends on the operating system, device
drivers, and TSR programs.  Professional-YAM on a PC XT can download
files or display screenfulls at 19200 bps without losing any characters
when run under DOS 2.1.  Under DOS 3.x, a few characters are lost, about
one in a hundred thousand.  When writing to certain disk systems,
characters can be lost at 2400 bps!  Emulation modes of trick EGA/VGA
cards are almost as bad.

Replacing the 8250 or 16450 UART ships with the new National NS16550AN
allows Pro-YAM to activate a 16 deep FIFO register.  This increases the
allowable interrupt latency by almost an order of magnitude.  It is
possible to send data to Pro-YAM at 115kb using ZMODEM, and get a
throughput of 70000-90000 bps; with an ordinary chip, the interrupt
latency caused by extended memory ramdisks causes data loss above 9600
bps.

Chuck Forsberg WA7KGX          ...!tektronix!reed!omen!caf 
Author of YMODEM, ZMODEM, Professional-YAM, ZCOMM, and DSZ
  Omen Technology Inc    "The High Reliability Software"
17505-V NW Sauvie IS RD   Portland OR 97231   503-621-3406
TeleGodzilla BBS: 621-3746   CIS: 70007,2304    Genie: CAF