A Casio in HP300s+ livery.
The friends at tiplanet.org, which is a French website devoted to Texas instruments machines, but that has several HP users that also post in hpmuseum.org, have uncovered that the HP300s+ share the very same firmware as the Casio fx–92 college 2D+.
You know that the lower level of HP scientific calculators are not 100% HP designs. To begin with, they don’t have RPN data entry mode; but we needed proof that they were designed by someone else. The tiplanet team had also seen the same firmware in a cheap Auchan calculator (Auchan is a french hypermarket chain, like Tesco in the UK, Aldi in Germany or Walmart in the US) However, apparently the quality of the circuit board in the latter was much lower than that of both Casio and HP models.
But there are additional functionality in the HP300s+, not accessible in the Casio. There is a menu for Hyperbolics through the Hyp key, a unit conversion menu via f–8, and with which units can be chosen based on rules written on the back of the calculator. These are functionalities that only appear in higher level Casio. So apparently the HP300s+ would not be an exact match of any particular Casio.
However, the tiplanet team opened up the diagnostics mode using the same key combinations. Both units showed the same firmware, “GY–468 VerA”, fully identical since both share the same checksum!
This means that all the functionality in the HP300s+ is also hidden in the Casio - it is just that the maker has decided to not make it available. How I hate equipment that has been deliberately clamped-down to adjust to market product roles!
By the way, it is also said that the HP10s+ is a Casio fx–85 clone…