Denial

yay!

some days ago i have started investigating the VIA a bit, with the intention of fixing VICE and chameleon. for a start, i am looking at the VIC20 for this, simply because its more convenient to run test programs on it than the 1541 drive.

in particular i am interested in the shift register right now - because it is generally not commonly used and documented less than great

so, what i am looking for is actual code that uses the shift registers - may it be small code snippets or full blown programs. anything might help with testing and/or improving the emulation (which i have just added - until now VICE didnt have them _at all_).

if someone is interested in the bloody details and perhaps help with test programs - let me know and i will elaborate

some tests i have come up with so far are here: https://sourceforge.net/p/vice-emu/code ... 20/via_sr/ - you can easily check yourself in VICE and see what a disaster the emulation is right now =P

@groepaz
Since it is documented that MOS VIAs and most other made in the 1980s had a bug in this shifter, are you going to test your software on the W65C22s and W65C22N which are reputed to have a fixed bit shifter ?

since none of my computers came with any of these - no. i'm only interested in reproducing the original behaviour exactly. (and for example find out what exactly those bugs are - which is also documented less than great)

groepaz wrote:... find out what exactly those bugs are - which is also documented less than great

Very true.

If I may suggest; having an IC that works the way it should have in the first place could help you document what doesn't work the way it should on MOS VIAs.

i dont think so - then i would have to test two chips in detail instead of one

I'm up for some of the gruesome details if you care to write it up here.