Re: A2 USB ?

[dempson@actrix.gen.nz (David Empson)]

Supertimer <supertimer@aol.com> wrote:

> be946@freenet.carleton.ca (Simon C.Hall) wrote:
> 
> >(Steve Mentzer) wrote:
> >
> >> Dont call me a skeptic, but I *highly* doubt that any form of apple II USB
> >> support will ever exist. Most USB-destined peripherals already have
> >> deeply-rooted support within the A2 line. 
> >> 
> >> And I highly doubt that the A2 bus could support the USB bandwidth spec.
> >
> >
> >There ARE USB <--> LocalTalk adapter's !
> 
> Then all we need is a driver....

Hardly.  LocalTalk is nowhere near fast enough to implement any form of
USB - not even the "slow" speed.  Any rumoured USB/LocalTalk adaptor is
intended to allow LocalTalk devices to work on a computer with a USB
port, not the other way around.  (I haven't heard of one, but I haven't
gone looking.  There are supposed to be USB-to-Parallel and
USB-to-Serial adaptors.)

In theory, a SCSI-to-USB adaptor would have sufficient bandwidth, but
the Apple II I/O bus bandwidth of 1 megabyte per second would be a
signficant problem (USB's top speed is 12 megabits per second, which is
1.5 megabytes per second).  There might be protocol related issues that
would prevent this working even if there was enough bandwidth.

It might be possible to implement USB in an Apple II by designing a new
interface card with its own microprocessor, providing buffering on the
card.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand