Slauri wrote: ↑Fri Feb 14, 2020 6:47 pm
The ULA warms up so much that it's painful to press your finger against it for over 5 seconds.
I don’t have a working issue 2 board to hand at the moment, but the ULA in an issue 1 board (soldered in) is similar. From being left switched off at a room temperature of about 20°C, and then turning it on, I can hold my finger on the central area of the ULA chip for only 37 seconds before it gets uncomfortable, then a few seconds later I have to remove my finger.
Once it has been on for a while, I can only hold my finger on the centre section for about five seconds.
It’s normal for these ULA chips to run hot. The internal temperature of a silicon chip can rise to around 100°C to 125°C and they will still work.
Part of the reason that this design of chip gets so hot, is that internally it operates at a voltage much lower than +5V. Around all four edges of the silicon chip inside the plastic package, there are lots of series pass regulators. Each of which produces lots of heat on their own. Plus there are lots of bipolar transistors switching at high speeds, these form the bulk of the digital circuitry, all of which produce a fair amount of heat as well.
For comparison, most modern chips use CMOS transistors, which run much cooler. In fact, a CMOS chip that is NOT running at a very high clock speed is cool to the touch.
So don’t worry about the temperature of the ULA.
Mark