[Coco] DriveWire issues with Coco 1 F/285 Board

[Aaron Wolfe]

On Tue, Jul 2, 2013 at 11:20 AM, Luis Antoniosi (CoCoDemus)
<retrocanada76 at gmail.com> wrote:
> Hi I already tested the DSK you sent me. Also I use an hdbdos built from
> toolshed.
>
> My problem seems to be on Drivewire server side. I need to set: ReadDelay =
> 1 and WriteByteDelay = 0 to have it properly working.
>
> I don't know about the speed cause i've never seem it running on a coco1
> but it seems to run fine now.
>
> Could it be related to the USB dongle I'm using is unknown, one thing is
> for sure: my DriveWire is pretty unstable even with coco2 or 3. Often it
> will get error reading and I need to restart the DW.
>

If this is a problem with your 741C then I am a bit surprised that
ReadDelay = 1 helps. That is creating an artificial 1 ms delay in only
one specific operation: between reading 4 bytes from the coco
requesting a disk sector and returning that sector's data to the coco.
 It can often take > 1ms just to fetch the disk sector, especially in
the case of remote images.  I use ReadDelay to simulate this and
usually set it to 200 or 300 :)

I would think that if the 741 is too slow to operate reliably at X
bps, then delaying it only at one specific point in a long transaction
would not improve things... right?

One difference between DW3 and DW4 is that DW4 will cache images in
RAM when possible.  Maybe this means that when the sector data is
already in ram, DW4 returns it so fast that the CoCo 1 needs a little
breathing room that wasn't necessary under DW3?  Adding only 1ms per
sector really isn't terrible (I wouldn't think?), so maybe that's just
how it is on some CoCo 1.

I would certainly try an alternate usb-serial adapter if possible.
You should also take a look at the adapter's settings.  Most have
several adjustments available for how they buffer, how often they poll
the usb bus, etc. Many FTDI adapters come with default settings that
are completely wrong for the type of communications that DW does.

Here is a video showing how to get ~30% faster performance with an
FTDI adapter.  These same type of settings might be the key to making
your adapter happy, I don't know.

http://www.youtube.com/watch?v=P8Ehm-J0LAA