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Re: [N8VEM-S100:5012] An ARM CPU on the S100 bus

On thing I wonder about with these modules, is is the GPIO fast enough to create a functional interface to the S-100 bus.  I have a few of the Raspberry Pi boards that run Linux and on the forums for that board the fastest "read speed" they can manage for the 26 GPIO pins is ~14 Mhz.  That is not counting any cycles to actually do anything with the information.

I know the typical S-100 bus speed maxes out around 10 Mhz so that might be totally acceptable.  If running standard, non-realtime Linux there is the always the chance that some process in Linux will eat up CPU cycles and make it so the process that is watching this "GPIO Pin S-100 Bus" doesn't get the CPU cycles it needs.  

I think it is worth some thought and a block diagram of how this might work before running off and doing it.  I could imagine two configurations, one where the ARM is a peripheral of the S-100 system like we do with the Propeller, the other where the ARM is acting as the master CPU and uses the Prop IO, etc as its inputs/outputs (I suspect the 2nd is harder to do in terms of re-routing Linux to use a GPIO-based bus for its keyboard and console).

The new Raspberry Pi B+ model has 27 GPIO pins available so we could also do a prototype board with a simple bus interface using those 27 pins (8-bit address, 16-bit data, and 3 control lines....).  That is a very well supported board and only $35.

On Sunday, August 24, 2014 11:21:35 AM UTC-7, monahanz wrote:
Thanks for the info gb.  Currently I'm leaning toward s the Technologic TS-4900.  See here:-
http://wiki.embeddedarm.com/wiki/TS-4900   and http://www.embeddedarm.com/products/board-pictures.php?product=TS-4900

They offer a mini-board with two 100  pin connectors on the back that would make the placement on an S100 board very nice.  The S100 board would be modeled after one of their "TS-Sockets"  and should in theory allow one to use a number of their "Computer on Module boards".      They supply a free IDE programming interface but somebody told me programming the I/O control lines is not easy.  There are 121 of them. Clearly plenty to control the critical S100 lines  for other S100 board I/O data etc.

An alternative I've been looking at is the European Olimex line, for example their A13 https://www.olimex.com/Products/SOM/A13/A13-SOM-256/

The advantage of them is they are more "hobby" oriented and supply much more information.  The down side is their boards don’t have the connectors on the back. The could be placed upside-down (not great) or perhaps removed and re-soldered.

Anyway early in the process,  I have currently started on an 80486 S100 board which I will do first.

Everybody out there, please feel free to supply suggestions as to "modern" CPU board you would like to see on the S100 bus.  If a cell phone can contain a powerful computer,  the is no reason our S100 boards cannot be one!

-----Original Message-----
From: n8ve...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of G. Beat
Sent: Sunday, August 24, 2014 7:13 AM
To: n8ve...@googlegroups.com
Subject: [N8VEM-S100:5012] An ARM CPU on the S100 bus

These System-On-Module (SoM) packages offer some interesting capabilities.
Ethernet / wireless support and integration on the S-100 card being a BIG Plus.

Connectivity is replacing most storage media for data/program transfers, such a board could serve the role as a surrogate for other S-100 boards.

Depending on implementation, an ARM based S-100 board (Linux) could also eliminate the need fir a separate PC to address -- uploads, interfacing, etc.

Intel's migration to NUC, now in their 4th generation, shows another paradigm shift and options.  It could sit inside a S-100 case -- or attached to back of monitor (VESA), being a super-smart terminal/workstation.


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