Re: Need help debugging IEC timing on #FujiNet

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Tue, 4 Apr 2023 20:08:00 +0200 Message-ID: <be38abfd-eaf2-8aae-24e1-190620fb4afa_at_laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 4/4/23 18:40, Thom Cherryhomes wrote:
> 
> What are the timing differences that can cause an absolute nightmare 
> between a c64 and a plus4? How does the 1541 deal with them?

Besides slightly different (and, in the Plus/4, variable) CPU clock 
speed, VIC in the C64 has 1 badline per character line on the screen 
while TED in the plus/4 has 2 since it doesn't have a dedicated 
connection to a color RAM like VIC does and has to load the character 
codes AND color information from main RAM in 2 steps

But a 1541 with standard ROMs will work reliably with a Plus/4. I'd take 
a look at the IEC code in the Plus/4 ROM to check for code that is used 
to adjust timings.

  Gerrit