Hi > > One interesting thing, found by Levente (I think), is that memory > > refreshes are like reads from $FF00-$FFFF. When the refresh was at > > $FF00-$FF3F, the program recorded the corresponding TED register values > > (although it was reading from the same constant address in open address > > space all the time). > > Ugh... Sure I did prove this refresh thing someway. But I don't remember > how. I'm sure you could have, but actually what Marko was referring to, happened on the Plus4 mailing list, and has been proved by me.... The method was a very simple one, as Marko already described in his mail. Just have a read cycle reading from a not-connected address space right after the refresh-cycle, and you will get the value what was on the bus in the refresh cycle. Then just do a mapping loop which does this for all refresh-cycle position, and the received data is easily analysable. It also proved, that the refresh cycle counter counts upwards, unlike the C64 where it does in the opposite direction. It happened around when we were talking about writing a program which runs in unconnected address space on the Plus4. > The same goes for the Plus/4. Just remove the vertical border with the > same trick you'd use on C64; if you switch the computer to single clock > mode, you can set the pattern the same way as in C64. But when enable > twiee clock, the borders will display the data fetched by the proc. And there is also a way, to have both TED and CPU drive the address bus at the same time, so both are active. (Actually they are active all the time, just when the cycle is not theirs they put $ffff on their address bus, to let the other device have it.) This happened to me by accident, and actually haven't got the time, yet to investigate, how it's reproducable.... Tibor Biczo - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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