[sdiy] TC5514 polysix memory...upgrade?

[Bob Weigel]

I have a ps6 that apparently has a dead one.  Can't store even when it's 
turned on.  All lines look like they are trying to do what is right.  
Not a bad board at all.  But someone had put a Li battery which is not a 
good idea of course.  But wouldn't think it would lead to dead memory 
but who knows maybe someone zapped it when they were installing the 
battery.

ANyway I was thinking it'd be cool to design even a simple daughter 
board that has leads for a switch that could be accessed somewhere 
non-intrusive that would give the ps6 more memory by switching a couple 
more address lines.  Does anyone know a compatible 4 bit data out chip 
that would pull this off with 16K or something? -Bob