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Old 15 December 2014, 15:48   #701
Amiga 500 User
Join Date: Jun 2013
Location: EU
Posts: 1,114
Originally Posted by Toni Wilen View Post
EDIT: MadeInCroatia for some reason does not immediately disable CIA-B interrupts when it takes over the system but only later and if TOD interrupt triggers during that period: crash.
So it will crash on WinUAE, but on a real A500 it will not crash, right? (this is what confuses me)

I found some general info about the bug here (probably you know for it) in "Time-of-Day (TOD) Clock" and "Errata" parts.

Due to a bug in many 6526s (see also errata below), the alarm IRQ would not always occur when the seconds component of the alarm time is exactly zero. The workaround is to set the alarm's tenths value to 0.1 seconds.

The 8520 revision of the CIA, used in the Amiga, modified the time-of-day clock to be a 24-bit binary counter, replacing the BCD format of the 6526. Other behavior was similar, however.

In addition to the aforementioned alarm clock interrupt bug, many CIAs exhibited a defect in which the part would fail to generate a timer B hardware interrupt if the interrupt control register (ICR) was read one or two clock cycles before the time when the interrupt should have actually occurred.
EDIT: In addition, found some more infos here:

the article: George Hug, Toward 2400 (Transactor Vol. 9, Issue 3 - Feb. 1989 p.62) (see in RS-232 bugs)

Last edited by amilo3438; 15 December 2014 at 18:19.
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