[Coco] DriveWire 4 'Turbo' ROM for CoCo 1??

[Darren A]

On Mon, Dec 23, 2013 at 9:25 PM, Chad H wrote:

> I was about to work on flashing a ROM for someone that has a CoCo 1 and
> they
> are interested in both the standard DW3 ROM (which I found in the archive
> at
> http://toolshed.sourceforge.net/snapshots/) as well as the 'Turbo'
> version,
> which didn't seem to exist in the ZIP.  I do recall something about the
> serial hardware of the CoCo's having different speed limitations.  Is the
> CoCo 1's serial not fast enough to support the Turbo mode?
>
>
The CoCo 1 cannot do Turbo mode without a hardware modification. The serial
port in those machines is limited to 38400 bps on the output side.

Recently I discovered that the current DWWrite code for CoCo 1 is
unreliable.  The timing drifts by 0.3 cpu cycles per bit and this is enough
to sometimes result in bad data alignment in the final bit of a byte.  Byte
values in which bit 6 is a '1' and bit 7 is a '0' seem most susceptible to
the problem.  For example, using the Basic statements below to write a
sector full of $55 bytes fails for me almost every time (don't try this on
a disk image containing important data):

A$=STRING$(128,&H55)
DSKO$ 0,0,1,A$,A$

I am currently testing a revised version of DWWrite to fix this problem.

Darren