ISSIE v5.2.0

One of the challenges in Issie development is controlling technical debt. As a project mostly extended by University student project work, the balance between adding new functionailty and refactoring always favours functionality. Luckily we also have some paid work from students over the summer period when we can ask them to spend time on the more boring but equally important stuff.

This Summer the Issie upgrades have been mostly about reducing technical debt and mending bugs. Last year updates to React 17 introduced a very nasty memory leak bug in Issie #463 that was undiagnosed for a long time and made use on large designs very unpleasant.

So this Summer we spent some time fixing this and in teh process instrumenting garbage collection and testing Issie with long simulations of large designs, and redoing everything that broke under those conditions.

The new feature this Summer is a greatly improved Waveform Simulator with a long overdue scrollbar (credit Samuel Wang's UTOP work) to navigate the time axis when viewing waveforms.

There are many changes in the Waveform simulator detailed in the release the release.

We also have added a nice built-in demo of the EEP1 CPU simulated for 800,000 cycles as hardware and running code to generate the first 20,000 prime numbers using Eratosthenes Sieve - which is great for testing the waveform simulation features.

In the process of this work we did some refactoring of the two areas in Issie most problematic for development because they have been reworked so many times; the simulation and the waveform simulator. Both of these now have a modular structure that reflects the real work done, and modules small enough to make finding things easy.

Tom Clarke, September 2024