Hi and thanks for this wonderful repository and also the related nerdone.it blog post.

I own a GVP 030 rev4 40 Mhz and this will definitely be very useful to replace the PALs with GALs and maybe try to overclock it a bit.

I have inspected the jpg of the 40Mhz rev4 card overclocked to 50Mhz and the only differences I can see is that a 50Mhz crystal is used, and that the mach has been burned to another chip (and placed in a socket). All the GALs remain the same as in the 40mhz not-overclocked.

This raises severral questions:

1. Why the change in the MACH chip? The files corresponding to the mach in 40mhz and 50mhz folders seem to be identical.

2. Is it really not needed to change the GALs? Many users tried to naively overclock their 40Mhz card by just changing the oscillator and they reported that the card does not work, because the PALs/GALs are different for the different card speeds.

3. I see that the only difference between the 040 and 050 JED files seems to be in the U36 IC (90C4 for rev4 40Mhz and 90C6 for rev3 50Mhz). Do you know if the rev4 card would work with the 90C6 IC and what would be the effect?

4. Finally I see that there is a commit related to a rework of the U36-90C6 using WinCUPL, and the resulting JED file seems indeed different to the original GJD uploaded previously (and my programmer reports different checksums when I load the JED and the GJD). What is the purpose of the rework? I guess this has something to do with what is stated in the nerdone blog post:

"È bene notare che questa tipologia di conversione è una “traduzione” della mappa di bit della Fuse Map: le equazioni non vengono estrapolate, l’ordine dei fattori non viene toccato e non viene eseguito nessun tipo di semplificazione.
Questo nella maggior parte dei casi può andare benissimo ma come abbiamo visto può essere necessario ottimizzare ulteriormente la programmazione con tool come WinCupl o OPALJR. Ma questa è materia per un altro articolo…"

Thanks again for the project and your time!