On Wed, 21 Mar 2001, William Levak wrote: > > I heard that the 6545 is not compatible with the 6845. But a long time ago > > I exchanged a 6845 with an faulty 6545 and the cbm worked again. Later > > swaps dibn't work. As I haven't this board anymore, I don't know for sure > > what 6845 I used but I thought an old original Motorola one. > > I have had the same experience. I have even seen some CBM's come from > Commodore with a 6845 in them. The 6845 has had a long run. There have > been many variations through the years, only some are compatible enough to > work in the CBM. The version that was current when the 80 column CBM > first came out seems to be compatible. I have tried earlier and later > versions and they are not compatible. I don't know the exact range of > versions that are compatible. 6845 versions are something the Amstrad CPC community are very familiar with. Ask on comp.sys.amstrad.8bit or maybe see the FAQ. Briefly, CPC users talk of 3 different varieties of 6845 CRC, all of which work in their CPCs but with varying levels of compatibility with certain programs. There seem to have been some changes with R/W# vs seperate RD# and WR# lines which affects whether an Amstrad with a particular 6845 can read its lightpen registers (read only registers). Also, I think there were some small changes in CRC timing which became important when Amstrad coders started playing with the registers for effects such as overscan. Richard - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail email@example.com.
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