Date: Thu, 4 Jul 1996 12:04:30 +0300 (EET DST) From: "Andrew V. Stesin" <stesin@elvisti.kiev.ua> To: bde@zeta.org.au (Bruce Evans) Cc: hardware@freebsd.org, isp@freebsd.org Subject: Re: muliport boards - building a PPP dialup server Message-ID: <199607040904.MAA23321@office.elvisti.kiev.ua> In-Reply-To: <199607032027.GAA15101@godzilla.zeta.org.au> from "Bruce Evans" at Jul 4, 96 06:27:05 am
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Thanks alot for the explanation, Bruce!
# source overhead relative
# ------
# serial interrupt overheads 3% per 11KB 1
# system overheads for termios raw mode input 3.3 1
# system overheads for cslip input 3.7 1+
# system overheads for pppd input 6.1 2
# system overheads for termios cooked mode input huge (50?) 16
#
# The system overheads are easy to reduce by replacing the 486/33 with a
# Pentium. The interrupt overheads are mostly I/O overheads so they are
# hard to reduce because boards with fast I/O are hard to find.
So an idea to get a PCI board seems to be pretty reasonable...
# > 2. ISA bus itself, no matter what will I put into it.
#
# This is the main bottleneck on anything faster than a DX2/66, at least
# if 8-bit I/O is used. The overheads for Comtrol RocketPorts would be
# about half as small because RocketPorts support 16-bit I/O.
Anyway, ISA is a dead-end, I think. (Consider the following:
16 ports seems to be an upper limit for ISA card at 8MHz, even if
it's 16bit "smart" one -- simply because it's ISA.
PCI has 33Mhz => 4 times faster,
it's a 32bit bus => add two times more. So PCI intellgent
card should be able to handle at least 8 times more ports
at full speed, => up to 128 ones! And just today I have
a headache -- we already have 16 ports busy on a dialup
server, what will I do when some 2 more lines will come?
Seems that getting a smart PCI serial device is the
easiest solution and a more reasonable investment than
a second server, considering added complexity of distributed
system).
# Bruce
#
--
With best regards -- Andrew Stesin.
Phones/fax: +380 (44) { 244-0122, 276-0188, 271-3457, 271-3560 }
"You may delegate authority, but not responsibility."
Frank's Management Rule #1.
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