[Coco] atari USB device

[jdaggett at gate.net]

Roger

One concern of mine, speed. The USB protocol does mention that packets can be 
sent without  handshake. To be honest that is a dumb thing to do but is an option. 
Even at 1.5 Mbps and with handshaking, the COCO at ~2 Mhz will be hard press to 
keep up on large packets of data from mul tiple sources and maintian rather fast 
"effective" data transfers. I think the Coco in fast mode can  handle a mouse and 
keyboard with little difficulty. Maybe even the joy sticks. But after that some of the 
processing will have to be offloaded into hardware and/or a second processor.

Faster speeds of USB 1.1 and USB 2 require an exteranl processor to handle the 
traffic and store data in a rather large buffer. Even today's fast processors will get 
bogged down  at 480 Mbps. Most USB 2.0 circuits I have seen have some hardware 
processor or a soft processor to off load the main CPU from  the task of handling 
the USB port(s).

The circuit from the Atari group is a simple circuit. It will require the most of the 
processor power and time to handle a large number of packets even at slow speed. 
>From what I  gather the concept was a simple and cheap way to get some USB 
functionality on the Atari. It looks as to me a first step. Keyboards and mice are 
relatively simple devices to place on a USB. They send small packets, Mice are 
three bytes of data. Keyboards have 16 bytes of buffer on them if I remember 
correctly. 

These type peripherals do not bog down the main processor in handling large 
number of pipes and large data transfers. If the group wanted a U SB Host that can 
handle many of the extra devices that h ave been mentined  you are increasing the 
complexity of the USB interface card by adding more hardware to offload the tasks 
from the CoCo.

james

On 17 Nov 2004 at 21:34, Roger Taylor wrote:

Date sent:      	Wed, 17 Nov 2004 21:34:06 -0600
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From:           	Roger Taylor <rtaylor at bayou.com>
Subject:        	Re: [Coco] atari USB device
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> Considering that Disk BASIC runs normally at ~1mhz and OS-9 at ~2mhz,
> and the USB 1.x (being the slower of the USB protocols) is pretty dern
> fast, the CoCo will not be able to use devices near as quickly as we
> do on a PC.  It might even be painfully slow for some devices.  But,
> you gotta admit, the whole idea sounds extremely tempting.