hy fellow hackers! i am investigating differences in the CIA behaviours (NMOS vs HMOS versions, ie 6526 vs 8521) at the moment. one thing that is pretty unclear to me, is a supposed bug in the TOD alarm behaviour. i can find some references to it on the web, which somehow look like one copied from the other to me - without ever mentioning the exact details: wikipedia: "Due to a bug in many 6526s 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." http://forum.6502.org/viewtopic.php?p=9837#p9837 "There was also a problem with the Time of Day clock alarm interrupt, which would not occur if the alarm time tenths-of-seconds was set to zero. The solution was to set the tenths to anything other than zero." ... "we" have created a bunch of test programs  in the past already, and they indeed show some odd behaviour under certain conditions (including the alarm not triggering when it should) - but so far these tests behave exactly the same on "old" and "new" CIAs. so i am asking you guys a) if you have heard about the above mentioned problem, and can tell details on the condition needed to reproduce it (so i can make it test program - or perhaps even you can provide one) and b) if this is really a problem that should only show on one of the two CIA variants (probably the older one). also if you know and references/documents that mention this problem, please tell!  https://sourceforge.net/p/vice-emu/code/HEAD/tree/testprogs/CIA/tod/ -- http://www.hitmen-console.org http://magicdisk.untergrund.net http://www.pokefinder.org http://ar.pokefinder.org Wer im Glashaus sitzt hat immer frische Gurken. Message was sent through the cbm-hackers mailing listReceived on 2017-03-08 18:00:07
Archive generated by hypermail 2.2.0.