This is a high score save for Time Pilot '84, the sequel to Time Pilot.
This upgrade exploits the "test chip" feature of the board, just like I've done for Time Pilot and others.
You don't replace any of the main program ROMs, you just put a new ROM in the existing extra socket on the board.
For this score save, however, you'll also have to replace one ROM that holds the code for a slave CPU.
And, of course, you'll need to replace one RAM chip with a non-volatile RAM to hold your scores safe.
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!!!
The first thing this game does when it boots up is look to see if a test chip is installed,
and if so, run that code. So I've taken advantage of this and re-written the boot routines to run in
that space. The new routines protect the high score RAM from being initialized and overwritten with
defaults. I've also skipped the exhaustive RAM and ROM tests that this game normally does, so it will
boot faster after this upgrade. This score save turned out to be a bit more difficult than the previous
ones I've done since the RAM that holds the scores on this game is shared by two CPUs, and they take turns
testing their ability to read and write the entire contents of that RAM. So I was forced to modify the
code of the slave CPU (which handles the foreground graphics) so that it skips its RAM testing.
I added the ability to reset the high scores by dipswitch selection. Like Time Pilot, this game doesn't
have any extra switches so I chose an unlikely combo to do the reset; all SW2 switches ON except for switch 3
(cocktail mode). I didn't add a corruption check, so you should us this dipswitch reset if something goes awry.
Here is what the table looks like when reset:
1) The 2K static RAM at location 9F 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, so you won't have to use the dipswitch reset for initialization.
2) The new high score save ROM (a 2764 EPROM) installs in the socket at location 6J. The existing main program ROMs (7J, 8J, 9J, and 10J) are left intact.
3) The new ROM for the slave CPU (another 2764 EPROM) installs at location 10D. Remove the existing EPROM and pop the new one in. That's it... you're done!
Price is $32 shipped in the US (international shipping available at additional cost).
Please email me to check availability before sending money.
For the do-it-yourself'er. If you've got your own programmer you can just download the ROM images
and burn your own EPROMs.
Donations are always appreciated. Buy me a beer (or two) to encourage further score save development. Thank you.