HP 48G+

HP 48
Company type	Product line
Industry	Electronics, Calculators
Founded	March 6, 1990; 36 years ago
Founder	Hewlett-Packard
Defunct	2003
Headquarters	Palo Alto, United States
Products	Graphing calculators (HP 48S, 48SX, 48G, 48GX, 48G+)
Parent	Hewlett-Packard

The HP 48 lineup, manufactured by Hewlett-Packard between 1990 and 2003, consists of sophisticated graphing calculator models designed primarily for engineers and professionals. Notable variants include the HP 48S, 48SX, 48G, 48GX, and 48G+. The G series are upgraded iterations of the S models, while the X suffix indicates models that support memory expansion through RAM and ROM cards—most notably the GX, which boasts greater internal memory capacity. The G+ versions further enhance onboard memory, whereas the SX and S share comparable base memory configurations.

Despite its similar designation, the hp 48gII released in 2004 is not categorized within this series but is instead associated with the HP 49g+ family.

These HP 48 calculators utilize Reverse Polish Notation (RPN) for input and allow programming with the RPL. Their hardware design influenced later HP calculators such as the HP 38G, which introduced a more user-friendly infix notation, and the HP 49G, which incorporated advanced software features. This hardware evolution can be traced back to earlier models like the HP-18C and the HP-28 series.

Models / Availability

The HP 48SX was introduced on March 6, 1990.

Production periods were as follows:

48SX: 1990 through 1993
48S: 1991 through 1993
48GX (F1895A): from 1993 until 2003
48GX ASEE: a special edition released in 1993 ("1893 ASEE 1993 Shaping our world - Century II")
48G: produced from 1993 to 2003
48G+ (F1630A, F1894A): available between 1998 and 2003

Specifications

The HP 48 series is powered by the Saturn CPU, a hybrid processor combining 64-bit and 20-bit operations with nibble-oriented data handling and addressing. The primary registers A through D and temporary registers R0 to R4 possess a width of 64 bits; meanwhile, data registers D0 and D1 operate on a 20-bit basis. External data retrieval transparently converts to physical accesses of 8 bits. Internally, the address bus spans 20 bits, but due to nibble selection, it effectively functions as a 19-bit bus externally.

Both HP 48S/SX and G/GX models incorporate the Saturn core within complex integrated circuits named after figures from the Lewis and Clark Expedition: the Clarke IC for S/SX models (named after William Clark) and the Yorke IC for G/GX models (named after Clark's servant). The preceding Saturn chip bore the codename Lewis.

Common features across all models

Processor architecture: Saturn
Display resolution: 131 by 64 pixels, available in three LCD variants offering improved clarity and contrast
Connectivity options: includes a 4-pin RS-232 serial interface (UART supporting speeds from 1200 to 9600 baud with parity settings) and an Infrared port (not compliant with IrDA standards)
External data bus width: 8 bits
Addressing capability: up to 20 bits, providing a logical address space of up to 512 KB
Maximum register capacity: 64 bits
Expansion slots on X models: two connectors each with 40 pins

Specifications specific to HP 48S/HP 48SX

Processor clock speed: runs at 2 MHz
Memory clock speed: also at 2 MHz
CPU codename: Clarke (Saturn core designated HP 1LT8)
Supported communication protocol(s): Kermit (protocol)
Internal ROM size: 256 KB
Internal RAM size: 32 KB
Maximum expandable memory via card: up to an additional 128 KB (exclusive to the 48SX)
ROM firmware versions: A, B, C, D, E, F, J
Shift keys colored orange and blue

Specifications for HP 48G / HP 48GX / HP 48G+

Processor clock speed: ranges from 3.68 to 4 MHz
- Initial production batches sorted CPUs into frequency categories: higher-speed processors (~3.93–3.94 MHz) were designated for expandable models (GX), whereas slightly slower variants powered the fixed-configuration units (G). Subsequent manufacturing improvements enabled nearly 4 MHz processors across all versions. Frequency variations due to temperature are negligible.
Memory clock speed: 2 MHz
CPU codename: Yorke (based on the Saturn architecture)
Supported communication protocols: Kermit (protocol), Xmodem
Integrated ROM capacity: 512 KB
Built-in RAM size: 32 KB in the 48G, and 128 KB in the 48G+ and 48GX models
Expansion memory limits: up to 128 KB via port 1, and up to 4 MB through port 2, with bank switching allowing access to 128 KB at a time
Available ROM firmware versions include K, L, M, P, and R
The shift keys utilize purple and blue-green hues, which may present usability difficulties for individuals with red-green color vision deficiencies

Programming

The HP 48 series employs RPL, a stack-oriented programming language that merges principles of Reverse Polish notation with elements inspired by Lisp. RPL enhances traditional stack-based coding by incorporating lists and functions, allowing unevaluated expressions to be pushed to or retrieved from the stack.

There are two forms of RPL: User RPL, which can be programmed directly on the device, and System RPL, which necessitates an external compiler provided either by third-party applications or Hewlett-Packard tools. User RPL enforces argument validation to prevent crashes but operates at a slower execution speed. Conversely, System RPL grants access to lower-level functions, offering faster performance but with increased risk of system errors if improperly used.

In addition, developers can program in HP Saturn assembly language using onboard utilities such as Jazz or external software like Hewlett-Packard's SASM assembler.

Emulators

Emu48 – Windows platform
Alcuin – Commodore Amiga environment
X48 – compatible with Mac OS X and POSIX-compliant systems (Unix/Linux)
i48 – HP48GX emulator for iOS, derived from X48
m48 – iPhone HP48 emulator based on Emu48
Droid48 – HP48G emulator for Android platforms, based on X48
droid48sx – Android emulator for HP48SX, built upon Droid48
HP48 emulator and decompiler – available for Unix/Linux or Windows (via Cygwin), developed by Paul Courbis

In popular culture

The HP 48 calculator is featured in the 2012 motion picture The Amazing Spider-Man as well as its follow-up.

External links