Is the Gemini Board compatible with the 8 MHz Z-100?

[ECNeilson]

I recently acquired a Gemini Board for my Z-100. Alas, after installing the card, I get the power-on beep and can hear key clicks but never get the boot ROM prompt.

I have the later version motherboard (#85-2806-1) that runs at 8 MHz so I'm wondering if the Gemini Board was originally designed only for the 5 MHz Z-100. I could also have a bad Gemini Board but before I dive into the card, I want to make sure I'm not wasting my time. Does anyone here remember if the GB runs at 8 MHz?

Thanks,
Eric

[Bob Groh]

Can't help on the Gemini board but your email sent me off on a web search ('gemini board z100') and I was amazed by all the information out on the Z100 family! I still have one Z100 up stairs and just might dig that puppy out some day and see if it still plays! Good luck on your quest, Eric.

Bob Groh
Heathkit engineer, ham radio group, 1977 to 1981

[ECNeilson]

I'm posting this detailed response from Steven of Z-100 Lifeline who emailed me with some tips. I was not able to get my Gemini board working but according to Steve, the Gemini board should be compatible with both models of the Z-100. I probably just have a bad Gemini.

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Regarding the Gemini Board, it works fine on an 8MHz Z-100, PROVIDED your Z-100 was working fine at 8MHz before, and you are using the same 8080 chip from the mainboard that you used when you removed it to install the Gemini Board. However, a couple of precautions:

* Make sure you installed the 8080 in the proper 40-pin socket. There are two sockets and the second one is for an 8086 coprocessor chip (not required for proper operation - this socket can be left empty).

* Make sure the 8080 is pointed in the correct direction. The notch must match with the painted half circle on the Gemini board's socket.

* On the Z-100 side, the Gemini is pretty much invisible - at least after the opening screen where you press {Z} for the native Z-100 and {P} for the PC Mode. I assume that you got this message fine and pressed the {Z} key.

* Make sure that you got the card inserted properly in the 8080 socket (it's easy to offset the card one pin, or to bend over a pin). These pins on the Gemini board are quite fragile, so DO NOT FORCE the board. If properly aligned, the board will fit with gentle pressure. Likewise, ensure the cables are connected back properly, but I don't believe that you would even get the opening GEMINI screen, if they weren't.

* When you press {P}, the card kicks in and takes over. The boot sequence is different. As I recall, you need to press {W} (for Winchester) and {0} for the unit number and then press {RETURN}.

* You must use ZENITH's version of PC-DOS. No other versions of PC-DOS will work. I