From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Osmialowski Subject: Re: Obsolete documentation? Date: Mon, 17 Feb 2020 14:10:48 +0100 (CET) Message-ID: References: <85e27a46-034f-f927-9169-e633c18909e8@gmail.com> <06A225A8D60249BC967DAD92CDEC4AF6@PotthastHP> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="98048-140800652-1581945048=:15349" Return-path: In-Reply-To: Sender: linux-8086-owner@vger.kernel.org List-ID: To: David Given Cc: Paul Osmialowski , Georg Potthast , Derek Johansen , "Marc-F. Lucca-Daniau" , ELKS This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --98048-140800652-1581945048=:15349 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: quoted-printable On Mon, 17 Feb 2020, David Given wrote: > On Mon, 17 Feb 2020 at 00:30, Paul Osmialowski wrote: > I'm using null-modem cable I've made myself and been using it for y= ears > (it corsses-over Rx/Tx and hardware control lines). It works nicely= with > Telix running under FreeDOS on my XT and minicom on 'big' Linux, at= speed > 115200, which is the top speed for 8250 chip on the XT side. >=20 >=20 > Exactly which 8250 is it? Some versions had major bugs which needed non-b= ackwards-compatible workarounds in the BIOS. If the ELKS driver doesn't hav= e these workarounds, which is likely if it's been targeted at later version= s of the 8250 which didn't have the bugs, > then it's likely not to work very well. I also believe (heard from Random= Person On The Internet) that driving an 8250 at high speed is difficult du= e to the very small buffer, and you need very good interrupt performance, w= hich I don't know if ELKS has. >=20 > Information on the different 8250s is here:=A0https://www.freebsd.org/doc= /en_US.ISO8859-1/articles/serial-uart/index.html >=20 In this particular case (Amstrad PC 2086) it's on-board Amstrad 40049 UART = (the same chip as used for a serial port in Amstrad Portable PC models), I = don't know any more details, except that all DOS programs (e.g. Norton SI) = report it as 8250. Yet at my old home I have Turbo XT with old, long 8-bit = ISA I/O card having two regular 8250's on it and as far as I remember, it=20 was the first time I experienced losing bits while communicating ELKS and=20 Linux running on a bigger PC. --98048-140800652-1581945048=:15349--