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.
Cheers, Qiwei Xiao qiwei@lucent.com