8.7  Upgrading the EPROM 

The software for the Gemini system is programmed into an EPROM that resides in the 

electronics box.  You can obtain upgrades for this software in two different forms: 

A new EPROM containing the new software 

A .hex file that must be programmed into a blank EPROM 

If you get the upgrade in the form of a .hex file, you will need a blank EPROM and a 

burner capable of programming it.  Gemini uses a 512Kx8 EPROM such as a 27C4001 or 

27C040. 

Once you have obtained a programmed EPROM (either 

by buying one or programming your own using the .hex 

file) you must install it in the Gemini system.  This can 

be accomplished as follows: 

1.  Unplug all cables from the Gemini electronics 

box 

2.  Remove the 6 screws that hold the faceplate onto 

the box 

3.  Remove the faceplate from the box 

4.  Identify the old EPROM on the board using the 

diagram to the right 

5.  Use a small flat blade screwdriver to gently pry 

the old EPROM out of the socket.  Be sure to 

loosen alternately from each end and avoid 

bending the pins. 

6.  Install the new EPROM into the socket.  Be sure that the notched end of the 

EPROM matches the notched end of the socket.  Ensure that all pins actually go 

into the socket and are not bent underneath. 

7.  Replace the faceplate and all 6 screws 

8.  Replace all cables 

Depending on the contents of the upgrade, you may see the message   CMOS Reset   

when you power up the Gemini.  This indicates that all parameters have been returned to 

factory defaults.  You will need to follow the procedures outlined in chapter 2 to re enter 

all of the setup parameters. 

Gemini Users Manual 

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