Stephan M�ller wrote:
The simplest method to switch between 2 Flash-memories is to connect both of
them and switch the CHIPENABLE-pin between the two flashs. Only the Flash
with the CE enabled will respond to requests. So there can be more than one
flash at the same address. Switching is done by connecting the
mainboard-CE-Connector to either one of the two flashs (CE-pin of them). A
simple switch can do this. And probably there can be more than 2 flashs the
same time connected (not enabled).
If somebody is interested in developing such a system, he can contact me, we
can try to do this, cheap and efficient for openBIOS-developers.
I actually made such a board and it has been working pretty well. The schematic
is exactly the same as the above. It uses a 32-pin cable connect to the BIOS
socket on the MB. The cable has to be short (less than 2 inches), especially
for fast Pentium. The switch has to be mechanical. (You might have thought
using some kind of TTL gate to switch the CE pin, this doesn't work, at least
for me, because of the delay it introduces). If anybody would like more
information, let me know so I can post details. (actually, there isn't too
much detail. Stephan said it all. )
As you still remember, I posted the EPROM simulator circuit to this list
some months ago. I actually managed to build the simulator and made it to
work!!! I did made some change to the original circuit. Again, let me know
if you are interested.