Dual TOS on STe (1.62/2.06): Cold start needs reset only 1.62

[stephen_usher]

An interesting aside from last night's swapping back on the PSU...

History:
A few months ago I fitted the dual TOS upgrade along with the Exxos "Red" PSU and set up the UBE switch on the reset button.

When switching on in TOS 1.62 mode the machine always required the reset switch to be pressed to get it to boot.

The common wisdom for this is that the capacitance in the reset circuit isn't enough to allow time for the Exxos PSU to supply the correct current. It was merely strange that it didn't seem to happen with TOS 2.06 selected.

Last night:
I fitted the extra capacitor to the reset circuit as detailed in these forums and also reverted to the original PSU so as to test if NetUSBee networking would work again (which it did).

I expected that the power-on reset issue would go away, seeing that the PSU was the original and I'd "fixed" the reset circuit. However, the same boot issue persist. i.e. if the machine is set to boot from TOS 1.62 it needs the reset button to be pressed otherwise it starts up in a crashed state but not if it's set to boot from TOS 2.06.

So, any ideas? (I'm not complaining, merely curious. It's not a major issue merely a minor annoyance.)

[exxos]

Its probably same issues as your other thread... https://www.exxosforum.co.uk/forum/viewt ... 233#p23234

I also assume you did the reset fixes on this page ? https://www.exxosforum.co.uk/forum/viewt ... =17&t=2175

[stephen_usher]

Its probably same issues as your other thread... https://www.exxosforum.co.uk/forum/viewt ... 233#p23234

I also assume you did the reset fixes on this page ? https://www.exxosforum.co.uk/forum/viewt ... =17&t=2175

Yes, that's why I wondered about the strangeness, especially as the machine didn't have problems with the original ROMs.

[exxos]

Yes, that's why I wondered about the strangeness, especially as the machine didn't have problems with the original ROMs.

Its just how unstable the machines are. Changing the CPU from MOT to ST brand is enough to break a machine. Same with ROM's or any other IC for that matter. Most of these issues are because the address and data bus resistors need to be 2.2K. I documented such issues many years ago and it just keeps tripping people up all the time. I'm going to class it as a mandatory fix in the tweaks and fixes section soon.