Fw: Cluster via USB

[Donald Becker]

On Sat, 3 Mar 2001, Mark Hahn wrote:

> On Fri, 2 Mar 2001, Jim Lux wrote:
> >The big problem with USB is that it is a "master/slave" kind of connection.
> 
> as I understand it, the direct-connect devices that exist now for ptp usb
> networking have a small chunk of memory that both masters can access.

That's not interface they present.  They have a Tx stream and an Rx
stream.  A common way to use them is to have the driver packetize the
data and make them look like a point-to-point Ethernet connection.

> don't see any reason that a USB2  device with a pair of significant-sized fifos 
> wouldn't work fine and remain cheap.  these days, quite large amounts of ram
> (32M or so) can be put on a single chip.

USB 2.0 will be high overhead and only about twice the speed of Fast
Ethernet.  We haven't seen USB 2.0 controllers, but USB v1 controllers
use the PCI bus inefficiently, especially in "bandwidth reclaimation"
mode.

I don't the market force that will cause USB 2.0 switches to appear, let
alone grow to support 500 (or even 16) devices.

Donald Becker				becker at scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993