Radioddity don't make their own radio hardware.
The radios branded as Radioddity, as just re-badged radios from other companies.
The GD-77 is actually a TYT MD-760.
The only differnce is that sometimes Radioddity pay for firmware customisations, and in the case of the GD-77 they commissioned a new CPS. i.e If you look at the TYT CPS e.g. for the MD380 or MD9600 it looks similar but is actually a complete re-write in C# whereas the TYT CPS's are written in C++ (using Microsoft Foundation Classes)
Although this looks a nice radio, I think they are missing a trick by it being DMR only. From what I've heard the new Connect Systems radios support, or will support D-STAR and other modes as well as DMR, albeit I think there is an additional free for each extra mode that is supported, becuase of the licensing costs.
Really, all these radios need to be switching to being SDR so they can be true multi mode e.g. including AM for Air Band and also SSB etc
But looking at the frequency range it looks identical to all the other radios which use the AT1846S FM only, TRx chip.
My guess is its got 2 x AT1846S TRx chips hence why it can do true dual standby.
Or if its like the new DM-1801 it may use 2 complete radio RF + CPU modules