Date : Sat, 31 Oct 2009 14:02:37 -0000
From : mu.list@... (Mark Usher)
Subject: Econet packet size
I did see recently an Acorn document saying
"the maximum packet size is 500bytes as set by the Econet Standards
Committee" (paraphrased)
Am just trying to look for it now. Obviously this seems to have been totally
ignored, and as Phil says there is no limitation within the protocol.
-Mark
> -----Original Message-----
> From: bbc-micro-bounces+mu.list=aon.at@... [mailto:bbc-
> micro-bounces+mu.list=aon.at@...] On Behalf Of Phil
> Blundell
> Sent: 31 October 2009 13:34
> To: Andrew Rowland
> Cc: bbc-micro@...
> Subject: Re: [BBC-Micro] Econet packet size
>
> The packet size has always been variable. OSBGET's poor performance on
> the original NFS was nothing to do with packet sizes, it was caused
> purely by the absence of any buffering at all in the NFS ROM (and hence
> the requirement for a round-trip to the fileserver for every byte).
> Even a modest buffer of 32 bytes or so would have made quite a
> difference to its performance.
>
> I can't immediately think where you might be getting the figure of 256
> bytes from; that doesn't seem to match up with any obvious protocol
> limitation.
>
> p.
>
> On Sat, 2009-10-31 at 11:09 +0000, Andrew Rowland wrote:
> > When did Econet start using variable packet sizes? Back when I as
> using
> > Beebs on Econet it was fixed at 256B, IIRC. Hence the poor
> performance of
> > OSBPUT and OSBGET until that school in Cambridge -- Newhall School? -
> - came
> > up a proper buffered version, which Acorn incorporated into the next
> release
> > of NFS. I remember that was a much-awaited upgrade! Barnsley LEA got
> the
> > chips in bulk to upgrade all the Econet stations in the LEA.
> >
> > Andrew
> >
> > -----Original Message-----
> > From: bbc-micro-bounces+famrowland=freeuk.com@...
> > [mailto:bbc-micro-bounces+famrowland=freeuk.com@...]
> On
> > Behalf Of Rick Murray
> > Sent: Sat, 31 October 2009 00:25
> > To: BBC MailList
> > Subject: [BBC-Micro] Econet packet size
> >
> > I remember recently a discussion on Econet packet sizes. Was idly
> reading
> > stuff on the MDFS server, and I came across this paragraph:
> > --8<--------
> > The econet is a low cost, moderate speed (50-300kBit/S on-net)
> network for
> > connecting together microcomputers. It allows one machine to transmit
> a
> > packet of data to another which has a suitable reception enabled to
> receive
> > that data. A packet contains at least one byte, and at most 1280
> bytes, of
> > data.
> > --8<--------
> >
> > Source: http://mdfs.net/Docs/Comp/Econet/RISCiX.txt
> >
> >
> > It is an undocumented Acorn document. RISCiX is an ARM based system
> that
> > was, I believe, a Unixy contender to RISC OS that never quite caught
> on.
> > The Rxxx workstations (looking a lot like souped-up A440s to me!).
> That
> > would date it late-80s. I would imagine the 1280 is likely a
> limitation of
> > the 6502-based machines, >1K is a lot in a 32K computer! At any rate,
> this
> > seems the Acorn-quoted value so reasonable to figure it is reliable
> enough.
> >
> > FWIW, skipping the ARM/RISCiX stuff, this document is a lengthy but
> pretty
> > complete introduction to the ins and outs of how Econet works.
> >
> >
> > Best wishes,
> >
> > Rick.
> >
>
>
>
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