Re: How much of a ][ is needed to twitch?

[bieling@terra.es]

M.J.Mahon wrote:
> >> I am assuming this is the case because the Disk ][ Controller has
> >> a reset generator that causes a longer reset pulse.  If there had
> >> not been an issue, this would not have been necessary.

On Feb 12, 12:59 pm, "Alex Freed" <a...@mirrow.com> wrote:
>
> > There *MAY* be a different explaination. Boot ROM at Cx00 is
> > only 256 bytes, so space is at premium. Better not to put a "soft"
> > delay there.


On Feb 12, 6:08 am, "mdj" <mdj....@gmail.com> wrote:
> Since the boot sequence is activated by the autostart firmware in the
> main system ROM, and autostart was added some time after the release
> of the Disk ][ this seems unlikely. Such a delay could've easily been
> added to the autostart routine.
>
> On a pre-autostart ][, such a delay is not required, since user
> interaction is necessary to initiate a disk boot.
>
> I'd imagine that Michaels hypothesis is the correct one - that the
> hardware reset pulse in the original Apple ][ is too short. It's
> possible that later revisions of the mainboard corrected the problem,
> since there were after all several versions, and it's an easy change
> to make.
>
> Matt

The disk II controller generates a 0.1 second power-up reset.
MLBs from rev1 and up generate a 0.3 second power-up reset.
Rev 0 boards do not generate a power-up reset at all.
"The controller generated reset was neccesary to achieve autostart
capability" (for rev 0 boards).
(James Fielding, Understanding the Apple II, page 9-13)

Jorge.