The HP-87 was the follow-on model to the HP-85 in the 'Series 80'. It was a logical development, keeping the same processor and clock speed, but with the following changes:
• Basic language extended ie long variable names added, support for larger graphical display, total 48K in ROM.
• Allows programs to address memory above 64K, through use of an extended memory controller.
• HP-87 has 32K RAM built in, and allows up to 4 extra RAM modules of either 32K, 64K or 128K ie 534K max.
• Built in HP-IB interface, together with software support for basic I/O, mass-storage and printing without additional ROMs.
• Bigger screen allowing 80 column text, with either 16 or 25 lines.
• No built in tape or printer.
• Support for multiple (up to 5) binary programs in RAM.
The HP-87 was followed by the HP-86 and HP-87XM. The HP-86 lost the internal monitor in favour of an external monitor, and lost the built in HP-IB connector in favour of a Centronics parallel printer port and two connectors for HP floppy disks.
The HP-86 also had 64K RAM while the HP-87XM included 128K RAM. The final machine in the series 80 family was the HP-86B, which went back to having a built-in HP-IB port and featured 128K of RAM.
Thanks to John Shadbolt and his site for this information