5 Jun
2014
5 Jun
'14
5:57 p.m.
On Jun 5, 2014 2:46 PM, "Chuck Guzis" <cclist at sydex.com> wrote:
The IWM certainly cost less than a 1770.
On 06/05/2014 12:17 PM, Eric Smith wrote:
> In 1983 it was still a lot less expensive for them to build a Woz
> controller than to buy a 1793 or 765/8272. The entire Woz controller
cost
less than just
the support components needed for a 1793 or 765/8272. It
became even more cost-effective when they started using the IWM ASIC in
1984.
Even cheaper than a simple WD1770? Almost no external support needed.
Still needed some 40mA drivers, didn't it? The industry-standard floppy
drives still used 150 ohm termination at that time. (I still don't really
understand how the later PC drives work reliably with 1K termination using
100-110 ohm impedance ribbon cable and no real control over the source
impedance.)
By using their own drive design, with only the cabling designed into their
products, and not having to support long cables or stubs, Apple avoided
needing high-current drivers. That might even have saved more money in
reduced PCB area than the actual components.
Since the 1770/1772 is in my 1984 databook and is not
labeled
"Preliminary" I'd assume it would have been available in 1982
at least in
early steppings to the likes of Apple.
I doubt it, though I don't have solid evidence. There should have been a
preliminary datasheet in late 1981 or early 1982 if it was sampling in late
1982. Apple would have needed working silicon in 1981 or early 1982 to ship
it in the Lisa in January 1983, unless they had found some good reason to
incur the cost of redesigning it very late in development.
Anyhow, once they designed the Woz controller into the Lisa, it didn't make
sense to change to something incompatible even if the cost was comparable,
which I don't think it was. They intended to use the Twiggy drives across
their entire product line, including the Apple II and III, though those
were cancelled.