Re: VIA shift register "bug"

Hi,

The problem is only with 6522 ie drives 1541 that do have VIA 6522, 
actually 1571 have it also for 1541 mode
and VIC20.


There is no problem in C64, C64 can go actually faster with burst mod 
wire patch
and kernel patch with drives like 1571/1581 (my preferred choice how to 
do it on C64)

Anyway I hope we will see fixed 6522 one or implement 6522 fix in our 
VIC20 and drives ...
It would be nice to see 6502 made again with all bugs and opcodes...


Best regards,

Zoran
On 2/3/24 17:08, Robert Di Benedetto wrote:
> Dumb question but - if WDC revs the mask and adds asynchronous support, does this mean that simply replacing the VIA's in the stock C64 and 1541 gets us faster I/O?  Or is additional modification needed?
>
> -----Original Message-----
> From: A. Fachat <afachat_at_gmx.de>
> Sent: Saturday, February 3, 2024 5:30 AM
> To: cbm-hackers_at_musoftware.de
> Subject: VIA shift register "bug"
>
> Hallo all,
>
>
> in case you haven't noticed, I have investigated the VIA shift register bug together with Dave McMurtrie and Martin Thierer, and got some news from WDC about it - all published in my latest two YT videos (still have to write it up...)
>
>
> The VIA shift register bug: https://youtu.be/6cwVQahVCdc
>
> The VIA followup: https://youtu.be/nvnz_34uWSg
>
>
> Oh, btw. I implemented the Commodore Fast Serial bus with a VIA shift register as well. Code is here
> https://github.com/fachat/via-sr-bugtest/blob/main/fiec/upet-fiec-core.a65
>
>
> Best regards,
>
> André
>
>