Sean Fahey wrote:
I'm not going to add anything to what Michael explained - he was very thorough - except for this: The ProSlot is a switched card. Only one slot on it is active at a time - originally, you flipped the power to switch cards. And I still want one, or two or three... I boot my IIe off CFFA, but on occasion I'd like to boot off SCSI. There are plenty of time I've needed one or the other but never at the same time. If the ProSlot and the Switch-A-Slot can be cloned and improved upon - I will be a serious customer.
Manually switching a slot prior to booting would be completely safe, from a logical perspective. The snag is making the slot switchable without having the inactive card disrupt signals on the bus. Normally, I would expect that transceivers (and other bus-connected logic) would have to be powered (but not enabled) to avoid loading the bus. This could be easily achieved by switching just the /DEVSEL and /IOSELECT signals, assuming that neither card does things on the bus without being requested (like IRQs). If an unpowered card can safely sit on an active Apple II bus, that would be interesting to know. -michael Music synthesis for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."