Lamar Owen lowen at pari.edu
Mon Dec 2 10:31:00 CST 2019

On 11/29/19 7:01 PM, Bill Gunshannon via cctalk wrote:
> Let's try again with the right name in the Subject line! It's not 
> really classic (although it does try to pretend to be but does anyone 
> here do anything with the P112 SBC? I am trying to get 8" disks 
> running on it but I am seeing some rather strange behavior.
Well, the P112 is a classic of sorts, being a mid-1990's design (much 
like the CPU280 from Tilmann Reh that I 'revived' a couple of years 
back, and still have PCBs leftover.... :-) ).  The P112 kit was, up 
until a few months ago, still available from David Griffith (661.org, 
which you've already found).  I bought two while I was buying a few 
years back, and built up one of them, which I still use a bit with a 
GIDE from Terry.  I am actually planning to port the TRS-80 Model 4's 
LS-DOS 6 to it for fun, but haven't had time to work too much with it.  
I was actually thinking about fabbing a few boards to try out faster 
Z80182 chips (officially there is a 33MHz version that has been 
overclocked by some to well over that speed) rather than risk 
desoldering the 16MHz '182 from one of the two kit boards I bought, so, 
for David Griffith's benefit, I would be interested in a bare board or 
three myself if he decides to fab some.  Sourcing the SuperIO and doing 
the fine-pitch SMD soldering will be a bit of a challenge, but worth it 
I believe.

As far as 8-inch drives are concerned, you would need to do exactly 
everything you would need to do to hook up an 8-inch drive to a PC, 
since the P112 uses a PC SuperIO chip for the FDC, and the floppy 
headers have PC pinouts and signal meanings (unlike the CPU280.....).  
The dBit FDADAP or similar would be needed to generate TG43 as well as 
translate the pinout correctly.  I haven't tried single-density support 
on the P112, so don't know if that would work or not, but the SuperIO 
chip used should be able to do that.

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