High Score Save


 Overview

This is a high score save for Juno First, another great Konami classic that doesn't get the respect it deserves! (some call it a Defender rip-off... but I'd rather play Juno First any day! But then again, I suck at Defender ;-) For this save you'll need to change one ROM and replace one RAM chip with a non-volatile RAM. The RAM chip you need to replace is unlikely to be socketed, so you'll have to remove the RAM and install a socket for the new NVRAM. If you don't have the soldering skills to do this, please find someone who does to do it for you. An experienced tech can do the job in under 10 minutes. You perform these modifications AT YOUR OWN RISK!!!

 How It Works

This game doesn't use a test chip, so we have to modify the code in one of the program ROMs. The code changes are fairly simple. However, this game (as well as others I'm currently working on) use the Konami-1 processor, which is a 6809E that uses encrypted opcodes. Simple changes become quite cumbersome....

Special thanks go to Chris Hardy (author of the Juno First emulator!) for writing the original score save and figuring out which RAM to replace. Chris was able to protect the high score RAM and skip the table reset by changing just 3 bytes:

  Load JFA_B9.BIN into a hex editor and make the following changes:

	Offset $004A = change $00 to $A0	(changes the RAM init to skip the HS data)
	Offset $00CF = change $2F to $9A	(these two bytes effectively disable the HS table reset)
	Offset $00D0 = change $A0 to $30
I added the ability to reset the high scores by selecting dipswitch 4 (unused, normally OFF) on SW2.
Only 25 bytes of code had to be changed. For those interested, here's the source for the code changes.

There are two versions of the Juno First code that I am aware of. There is the original Konami and a version licensed to Gottlieb (obvious on the title screen). Make sure you use the appropriate version of the high score save ROM (both ROM images are included in the zip file below).


 Installation

1) The 2K static RAM at location 8B on the CPU board needs to be replaced with a non-volatile memory. If that chip happens to be socketed then this step will be a breeze; just pop out the RAM and plug in the NVRAM. If not, then you'll have to remove the chip and install a socket. For the NVRAM you could use a battery-backed SRAM like the Dallas DS1220 or the ST M48Z02 (or M48Z12). Or you could use a newer technology that doesn't rely on batteries, like the Simtek 25C48 or the ZMD U63716 [NOTE: these two chips have been out of production for several years, and are no longer available], which have a 100+ year data retention.

Once you've got the new chip installed I suggest you test the board at this point to verify that your socket installation is good. The game should play normal. This step will also put good data in the high score table.

2) The new high score save ROM (a 2764 EPROM) installs at location 9B, right beside the RAM you just replaced. Remove the existing EPROM and pop the new one in. That's it... you're done!



 Kits

High score save kits are built on demand. They contain:

Price is $32 shipped in the US (international shipping available at additional cost).
Please email me to check availability before sending money.


 Download

For the do-it-yourself'er. If you've got your own programmer you can just download this ROM image and burn it to a 2764 EPROM.

download the ROM image

Donations via PayPal "gift" payments (to osborn@alum.mit.edu) are always appreciated. Any money received goes right back into my arcade and score save development. Thank you.


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