Re: AE HD+ driver

[Wayne Stewart <waynes@intergate.ca>]

"Michael J. Mahon" wrote:

> Sounds like that 24- or 28-pin socket may not have held an EPROM, but
> a gate array of some kind.  Wayne could verify that, since his drive is
> almost certainly very similar.

I think I phrased my posting in a misleading way, There's not only no
EPROM, there's no socket for one in my AEHD drive

> The 1600KB format is just Apple GCR with twice as many sectors per
> track (number depending on zone).  This is accomplished by doubling the
> data rate, which should be automatic with HD disks.  Making RWTS work
> would take a few changes, but nothing drastic.  The real issue is getting
> an IWM chip to run at double data rate.  I expect it would work if clocked
> faster, but it would certainly tighten up the margins for grabbing the data
> bytes, unless this is done by hardware (and buffered in an SRAM).
>
> All in all, a lot of trouble to get another couple hundred KB on a disk,
> compared to 1.44MB at constant speed and fixed sectors-per-track.
> Of course, this also requires hardware data capture and buffering,
> as in the SuperDrive Controller.

I don't think that was the case, I believe the AEHD drives hit the market
just before the SuperDrive cards were released. So in that case it would
have been 800k versus 1600k. Of course since it needs a driver you can't
boot off a 1600k disk though you can get around that for GSOS if you
preboot off an 800k disk. At more than $100 less than the Apple 800k
drives, it surprises me that there aren't more AE drives around.

    Wayne