
HP calculator museum: HP48s/sx Graphing Calculator, 1990

The HP-48 is a series of graphing calculators using Reverse Polish notation (RPN) and the RPL programming language, produced by Hewlett-Packard (HP) from 1990 until 2003. The series include the HP-48S, HP-48SX, HP-48G, HP-48GX, and HP-48G+, the G models being expanded and improved versions of the S models. The models with an X suffix are expandable via special RAM (memory expansion) and ROM (software application) cards. In particular, the GX models have more onboard memory than the G models. The G+ models have more onboard memory only. The SX and S models have the same amount of onboard memory.

Specifications
- CPU clock frequency: 2 MHz
- Memory clock frequency: 2 MHz
- CPU codename: Clarke
- Communication Protocol(s): Serial Transfers: Kermit (protocol); Infrared Transfers: proprietary
- On-board ROM: 256 KB
- On-board RAM: 32 KB
- Maximum additional memory per expansion card: 128 KB (SX only)
- ROM versions: A, B, C, D, E, J
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