P112

[David Griffith]

On Sun, 8 Apr 2018, Fred Cisin via cctalk wrote:

>>> Should be fun.
>>> Is the FDC a 765 variant?
>>> or a WD 179x variant?
>
> On Sun, 8 Apr 2018, Bill Gunshannon via cctalk wrote:
>> SMC 37C651.  Supports  500 Kb/s, 300 Kb/s and 250 Kb/s Data Rates.
>> Something else we lost with the PC.
>
> That's a 765 variant.  Made by several companies, even WD!
> Most of those can handle FM/"single density".
>
> 5.25" single density is 125K bps
> It might support it,> Should have left it the way it was and have people set 
> the Drive Select
>> themselves.
>
> in spite of not mentioning it.

All the P112 boards I distributed use a FDC37C665IR super-IO chip from 
SMC.  I don't know which variant David Brooks used.  I never acquired one 
made by him.  In case anyone wants more P112s, it's that chip that's the 
big sticking point for why I don't have anymore.  The board stuffer's 
robots had problems dealing with pulls.  The legs had to be absolutely 
perfect, so I had to get new-old-stock chips.  I've recently discovered 
how to do a good job of soldering QFPs by hand, so maybe I could work that 
angle.

The weirdness of the how the floppy drive cabling works with the P112 had 
me baffled for the longest time.  Terry and I thought it would be best 
though to just leave those quirks alone when it came time to update the 
firmware.


-- 
David Griffith
dave at 661.org

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