[uCsimm] RE: [uClinux-dev] BEWARE: Lineo 68360 board

From: Michael Leslie (mleslie@lineo.ca)
Date: Thu Nov 23 2000 - 12:09:06 EST


On Thu, 23 Nov 2000, Paugam Luc wrote:
>
> What i mentionned is to better use a MC68EN360 at 33MHz due to the 30Mbits/s
> bandwidth between the CPM and the CPU core. Thereby, you should have the
> maximum performance of your 3 Ethernet channels, whatever you product is
> dedicated for (router, data injection ...etc). However, i see no interest to
> offer Ethernet channels with a bandwidth divided by a factor of 3 or 5!
>

Aha, perhaps I wasn't too clear on the configuration of our board. In its
current incarnation it only has one ethernet port; the three other SCCs
are connected to serial transceivers (sipex) that are configurable for
RS232, V.35, RS422, etc.

> But for 3 Ethernet ports at the maximum bandwidth (10 Mbits/s), i
> successfuly designed a CPU that integrate a MC68EN360 at 33MHz in companion
> mode with a MC68EC060 at 66MHz.
>

Very nice. Have you considered running uClinux on it? ;-)

By the way, I think I'll post subsequent messages in this thread to
uclinux-dev only; I'm annoying even myself with all these cross-posts ;)

Cheers,
Michael Leslie,
Lineo Inc.

>
> > -----Original Message-----
> > From: Michael Leslie [SMTP:mleslie@lineo.ca]
> > Sent: Wednesday, November 22, 2000 7:14 PM
> > To: Paugam Luc
> > Cc: 'uClinux Mailing-List'; 'uClinux-dev Mailing-List'; 'uCsimm
> > Mailing-List'
> > Subject: RE: [uClinux-dev] BEWARE: Lineo 68360 board
> >
> >
> > Luc,
> >
> > It's not quite true that you cannot configure the 68en360 for more than
> > two Ethernet ports. You can do so, but you are limited, as you observe, to
> > an aggregate throughput of about 20Mbps.
> >
> > I would refer anyone interested in the gory details to the 360 manual,
> > appendix A: "Serial Performance":
> >
> > http://www.mot.com/netcomm/aesop/683XX/360/360UM-P3.pdf
> >
> > and also the "CPM Performance Spreadsheet" and accompanying documentation
> > at:
> >
> > http://www.mot.com/SPS/RISC/netcomm/tools/index.html#68360_table
> >
> >
> > As an example, a router with multiple ethernet connections to 2Mbps DSL
> > modems, would be well within the limits. From Motorola's worksheet, the
> > following configuration yields ~73% CPM usage for a 25MHz part:
> >
> > Ethernet on SCC1, 10Mbps throughput
> > Ethernet on SCC2, 3, and 4, 2Mbps throughput
> >
> >
> > The perormance of the CPU core should, in an application like a router,
> > have little to no effect on the throughput of the communications
> > engine. As long as CPM interrupts are serviced quickly, and the amount of
> > buffer copying is kept to a minimum, fully loading the CPU should have no
> > effect on data transfers. This is the basic idea behind the '360, of
> > course. If the CPU core is performing significant manipulation of the
> > rx/tx data, then of course it will become a bottleneck. But then a 25MHz
> > 68k core is no DSP...
> >
> >
> > Cheers,
> > Michael Leslie,
> > Lineo Inc.
> >
> >
> > On Wed, 22 Nov 2000, Paugam Luc wrote:
> >
> > >
> > > BEWARE If you use a 25MHz Motorola MC68EN360, you cannot have 3 Ethernet
> > > ports due to the bandwidth between the CPU core and its CPM
> > (Communications
> > > Processor Module). It is about 22 Mbits/s.
> > > You better should use a 33MHz chip: the bandwidth between the CPU core
> > and
> > > its CPM is 30 Mbits/s (OK for 3 LAN/WAN ports).
> > >
> > > Generally it is not a good idea to design a CPU with more than 1
> > Ethernet
> > > port, with only a MC68EN360.
> > > This uP is not very fast: at 33MHz, 6 MIPS, 10500 dhrystones/second (5.5
> > > BogoMips on uClinux). You have not enough power to fill up 2 or 3
> > LAN/WAN
> > > ports and to execute apllications.
> > >
> > > In order to remedy this fact and to really use 2 or 3 LAN/WAN ports, you
> > > need to use your MC68EN360 at 33MHz in companion mode with a MC68EC060
> > at
> > > 66MHz.
> > >
> > > Best Regards
> > > Luc
> > >
> > > >Michael Leslie [SMTP:mleslie@lineo.ca] wrote:
> > > >
> > > >For those interested in Lineo's MC68360 board.
> > > >
> > > >The device is designed to be a high-end T1/E1 router platform.
> > > >For availability and pricing, please contact Jim Stewart
> > > <jim.stewart@lineo.com>
> > > >
> > > >Again, this board's vital statistics are:
> > > >
> > > > - 25MHz Motorola MC68EN360
> > > > - 32M DRAM
> > > > - 8M FLASH
> > > > - 10-base-T Ethernet
> > > > - Serial console
> > > > - 3 highly configurable WAN ports
> > > > - IDE interface
> > > > - Nice and small; designed to mount on a laptop hard disk
> > > >
> > > >
> > > >Cheers,
> > > >Michael Leslie,
> > > >Lineo Inc.
> > >
> >
> >
> >
> >
> >
> >
>

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