Hypothesized Official Name: plotSScreen
Memory Address: 987Ch
Length: 768 bytes
This appears to be the same as the old plotSScreen. It can generally be used for scrap RAM.
plotSScreen used to be used for storing a bitmap image of the graph screen. It is clearly not large enough to be used for that purpose now.
The OS never appears to touch this area. I suspect it's here at the behest of the Verilog and/or IQ Joe guys, in order to give them (and by extension, us) scrap RAM.
See also saveSScreen for another 768 byte block of scrap RAM.