@Frank, no problem! Best regards from Esslingen. I just was not too happy, because I think the idea is not completely silly and because it takes some time for me to write - especially in English.
@Paul: This forth system has nothing to do with my suggestion. It is just my background: Seeing the sd as a central part of the system and loading code from it is just natural for me. Actually I was rather disappointed, when T4.0 came out without SD-Card....
I try to describe the idea better:
Background and intended usage in my case:
I have a program written with Teensy-Arduino running on T4.1. It uses a sd card for a configuration file. Part of the sketch is a Forth System, but that is irrelevant here. Teensy is used to control an analog Guitar Effect. Sets of Parameter- Values can be stored and recalled to achieve different sounds quickly. With Midi, it will be possible to do this for several units in parallel.
Perhaps google can translate:
https://musikding.rocks/wbb/index.php/Thread/420527-Midi-und-Parameter-Steuerung-für-Analog-Effekt/. As you can see there, due to the Open Drain - high Frequency PWMs, the Hardware Interface to the Vactrols (LED+LDR) is really totally simple. Only RC. And it is very flexible, it can control anything, that has potentiometers up to 150 Volts. Once the program is in the teensy, you only need to adapt the configuration file to your analog effect. T4.1 has a large number of such PWM-channels, which is great. The high frequency is essential, because you can filter it easily and you cannot hear noise. Guitar electronics is very sensitive, because you have high gain. The sketch needs 85k code at the moment + 115k variables, which includes the big memory for the forth vocabulary. So this fits easily into Ram.
Need:
The people, who are active in this "Musikding" forum are very fond of analog guitar effects and tube amps. They do not program. Many can just solder and cannot read schematics. But some use Midi already with bought effects. I now have thought, how I could make the programmed controller available. I could buy some, program them, distribute them. But if I calculate some none-yoke hourly wages and the shipping, this will get expensive quickly.
So the idea would be:
If pjrc would bring a SD-bootloader into every T4.1, they sell, software-distribution and hardware-distribution would get independent as it is done for other sorts of computers. This SD-bootloader would search for a sd-card, search for a certain program name, load an executable program-file (written as Arduino sketch) from SD-card at every startup. Software-updates can be done without a PC connected. People, who do not program controllers, can turn a T4.1 into a fixed function chip more easily. (I do have the impression, that the number of people, who do programming is not increasing.)
Of course this is a long-term suggestion.
Hoping, that I could make the idea more clear. Regards Christof