MEM11 Status Update

Guy Sotomayor ggs at
Tue Jan 20 18:57:27 CST 2015

On 1/20/15 8:02 AM, Noel Chiappa wrote:
>      > From: Guy Sotomayor
>      > I'm using FRAM.  They have unlimited write cycles
> Although I hear the latest flash have very, very large numbers of write
> cycles. But if you can get large enough FRAMs, yeah, they seem like a better
> alternative.
>      > I didn't want to have any sort of removable media as that bring its own
>      > sets of challenges.
> Oh well, back to loading all the bits in over a serial line (although I
> suppose if one has some other removable media drive, e.g. a RX02, one could
> get the bits in that way).

It's not all that bad!  ;-)  When in UI mode, it'll support 115200 bps.  
When in emulation mode
you'll be limited to 19200.  Since the J1 has to process each character 
as it comes in from the
UART, that takes time from emulation of other Unibus requests (so memory 
latency will go up
slightly).  Going too much faster and it would probably be noticeable 
and besides the PDP-11
probably won't keep up (at least and do very much with the characters).
>      >> (Or perhaps even a front-end running on a PC which is connected to
>      >> the MEM11 over the serial line.)
>      > That was my original thought (command front end) but that would mean
>      > writing/supporting a bunch of different programs for different
>      > OS/platforms
> Well, probably only at most two (Windoze and Linux), and maybe only one (since
> there are Windows emulation packages for Linux). Although if one stuck to a
> line-oriented interface, something like CygWin would allow one to have only
> one version.

I do everything on a Mac.  :-P  Having ported "Unix" programs between 
Unix/Linux on various
occasions, it's the details (like where header files live) that cause 
problems.  I'll leave it up to
someone else to do that.  ;-)

Oh, and one last thing that I forgot to mention.  I'm building a "LED" 
board that attaches to the
MEM11.  The LED board will display all of the indicators for the RF11 
controller in a layout similar
to what was on a real RF11.  I couldn't resist more blinkin lights. ;-)  
It's optional and will
connect to the MEM11 with a small cable (I plan on using RS485 drivers 
for the cable) so the
LED board can be a fair distance away.  It'll fit as a 19" rack panel (I 
haven't looked at doing
an overlay to make it look pretty) but it'll be somewhat generic (4 rows 
of 36 LEDs).

TTFN - Guy

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