Monday, January 16, 2012

First running program

I have some very exciting news to share. The emulator connected to the console panel has just run a rudimentary IBM 360 program.

Chris Bigos has provided me with ROS listings and control field definitions for the IBM 7201, an improved version of the model 65 used in the IBM 9020 complex, which was developed for the FAA for air traffic control.

Based on that information, I've put together a partial (very incomplete) emulator that is capable of running a simple 2-instruction program that counts up from 0. The program can be toggled in from the console panel. I will try to post a video tomorrow.

The new emulator sources can be found on the wiki at

Saturday, January 7, 2012

Software update

I've put a first version of the beginning of the emulation code on the Wiki at Based on the information Chris has provided so far, I think I have a fair idea of what the emulation loop needs to look like. Only a few of the many micro-orders, and none of the actual ROS contents have been filled in.

Thursday, January 5, 2012

Wiki updates

I've updated the microachitecture Wiki with some information that Chris Bigos provided me with at his site. He provided me with scanned sections of some of the field engineering docs. I was able to add information to the microarchitecture, ROS and working registers entries. A big thank-you to Chris.

Wednesday, January 4, 2012

Software plans

So here it is, the plans for the software that I promised on New Year's Eve.
Rather than writing an emulator from scratch (something I've done a few times before, see ES40 and FreeAXP for examples) I'm going to modify an existing emulator, the Hercules System/370, ESA/390, and z/Architecture Emulator. Whew, that's a mouthful! It emulates an IBM 370 or later rather than a System/360, but as the 370 was downwards compatible, OS/360 will run on Hercules.

I like using Hercules with an add-on application called Jason. Jason is a graphical front-end to Hercules, that provides you with a view of the (virtual) devices attached to the emulator. It allows you to change a tape, or load a deck of cards using the mouse on the devices, rather than typing commands at the Hercules prompt. Having a Jason display running on an LCD panel next to the console panel seems to be a good way to show the rest of the 360 environment.

I'll make two modifications to Hercules. The most obvious change will be to equip Hercules with an interface to the real console panel. The more subtle change will be to replace the emulated 370 CPU with an emulated 360 model 65 CPU. The feasibility of doing this depends on my ability to find the proper documentation on the model 65's microarchitecture (see the Wiki for an overview of the microarchitecture).

The emulated cpu will no longer execute one entire System/360 instruction at a time, but one ROS microprogram instruction. Depending on the setting of the console panel switches, after pressing the START button, the system will keep executing instructions, execute a single System/360 instruction, or execute a single microprogram instruction.

Switch to Arduino

Just when I thought the hardware part of this project was finished, as I turned to the software part of it, I discovered that the Velleman IO kit I used is way too slow for what I'm trying to do. It takes around 1whole second to read and write all the data (24 bytes in, 40 bytes out). This is way too slow; it means that a change in the switch settings will be reflected by the lamps up to two seconds later. It also means that pushing a pushbutton for less than a full second might not be picked up. Grr....

So, over to plan B, which is to use an arduino. With the proper cables, it should just plug into the electronics kit like the Velleman K8060 did. I'll use it with the Ethernet shield, so the console pannel can use a network connection to the emulator pc rather than USB. With the Arduino, I believe I can get the response time down to 1 millisecond.

Monday, January 2, 2012

IBM 360 movieclip

This short movie shows me going crazy programming the console panel lights... Have fun!

Sunday, January 1, 2012

IBM 360/65 Microarchitecture Wiki

First of all, hapy new year to all fellow tinkerers, collectors and enthousiasts.

I've set up a Wiki at with information about the model 65 microarchitecture. Hopefully, I can find the information to keep adding to it to build a complete picture of the model 65 microarchitecture. If you're familiar with 360's, or have suggestions as to what certain bits might mean, feel free to join the wiki and contribute.