🚀 go-pugleaf

In article <PCG.91Sep9185229@aberdb.aber.ac.uk> pcg@aber.ac.uk (Piercarlo Grandi) writes:
>cpcahil> Throughput is not the only evaluation factor for a disk
>cpcahil> controller.  Another factor, which is where a good EISA
>cpcahil> controller will shine, is the amount of time the bus is tied up
>cpcahil> transferring that 4MB/s.
>
>Latency then perhaps matters. But in practice not a lot...
>
>cpcahil> You yourself said that the theoretical max for the ISA bus was
>cpcahil> between 5 and 6 MB/s.  4MB/s is appox 80% of the theoretical
>cpcahil> max.
>
>Of course, but this is nearly irrelevant. Almost nobody keeps their SCSI
>bus running at its top rated bandwidth continuously (not even Adaptec,
>which stay off the bus for some programmable fraction of the time).
>
>In particular disk access tends, in normal operation, to be bursty (the
>effect of caching and paging, and then of intervening seeks).
>

That's because the CPU is too busy waiting for the controllers (disk and
ethernet) to accept the data so it can work on getting something else
ready to send.  Even if no single piece is any faster, it frees the
processor that much quicker.  Granted, under dos you will not notice
any significat difference.  A Novell 386 server, or Unix, etc... will
take advantage of it.

I don't think anyone listed all the specs for Cisco routers.  Here are some
more for the AGS+.  They demonstrated protype software in October 1990 that
could forward more than 74,000 pps total in multiple streams.  The reason
for these speeds, is it's possible to put over 24 ethernet ports on
these boxes, or FDDI.  There is a 16 MIPS Bit Slice processor per interface
card, the main CPU is a 30 Mhz 60020, and the C-BUS controller also has a
16 MIPS processor.

Back to the original topic...  If a dedicated 10Mbs per computer is
wanted, he would save much money with high speed bridges.  There are some
that can take upto 7 ports and handle full ethernet speed on all ports.
By using multiple bridges you could have any number of available ports.
These devices cost considerably less than an equally equiped router.
Routers are best to keep the broadcasts down, but if you have only a small
number of machines per segment, than that isn't needed.

Also if he was considering anything less than an AGS+ (even an AGS) then
it would probabbly be better not to use any router at all if the number
of machines is sufficiently small.  (Was the number ever stated?)