Sunday, December 7, 2014

Wiring up power supply of the SAC Interface box


I ran the circuit simulations with the 5V supply to my circuits reduced to 3.3V, to simplify the link to the FPGA board which is easiest to operate with 3.3V logic levels. Everything worked well, thus I will drop the use of +5V for my logic levels and instead use 3.3V for the FPGA side and regulate the 5V source down to +3V for the SLT side.

Heat shrink over solder joints, connectors now in place
Filter capacitor for 3.3V FPGA side supply
Filter capacitor for 3V SLT side supply
I installed the filter capacitors and wired up all of the power lines except for the 3V voltage regulator which is on-order. I set up a barrier strip to wire in the regulator, allowing me to set up all the other wires. There are just a few remaining tasks before I test and then begin using the SAC Interface box:

  • Wire the case fan to the 12V and ground lines
  • Finish the mounting brackets for the 26 pin power connector
  • Install the 26 pin female connector that brings the 1130 power and EPO lines to the box
  • Build and install the 3V voltage regulator
  • Secure the 24V relay inside the case
  • Hook up the front USB port cable to the FPGA's UART micro USB connector
  • Connect the second front panel USB port to the FPGA programming micro USB connector
Nearly complete now - just a few tasks remaining


  1. The SAC (Storage Access Channel) is an interface from the 1130 giving all the signals needed to implement any peripheral interface to the system. It allows me to add devices to the 1130 that weren't part of my machine's configuration.

    For example, I have built paper tape reader and punch devices, but the adapter logic is not included in my 1130. I can implement IBM's adapter logic inside the fpga, hook up my reader and punch, giving the system what appears to be the IBM 1134 and 1055 devices.

    I have some DEC RK05 drives which are similar to the IBM 2310 disk drives (and the internal disk drive). I can set up an emulating adapter to hook those up so my 1130 thinks it has some 2310 drives.

    I also have a plotter which will operate like the IBM 1627 plotter using IBM's adapter logic implemented in this interface box - since my physical 1130 does not have the plotter adapter logic cards installed.

    More interestingly, I can emulate devices and the IBM adapter logic, such as the 1403 printer, but actually spool the print output to a PC over a USB link. Same with an emulated 2501 card reader, passing it card images from the PC. This will free me from having to physically punch holes in cards, read them in, then smear ink on dead trees to see the results.

    I designed this to be flexible, allowing multiple devices to be implemented and to allow other 1130 owners (several museums and collectors have machines that either are running or could be restored) to use a copy of this interface. I will publish all the design information and code as open source once I have it working properly.

  2. Thanks, Carl. I had suspected as much. Very cool. Look forward to it running the first device!