HP 48GX

HP 48 series
Company type	Product line
Industry	Electronics, Calculators
Predecessor	HP-18C, HP-28 series
Founded	March 6, 1990; 36 years ago
Founder	Hewlett-Packard
Defunct	2003
Fate	Discontinued
Successor	HP 49g+
Area served	Worldwide
Products	Graphing calculators (HP 48S, SX, G, GX, G+)
Owner	Hewlett-Packard
Parent	Hewlett-Packard

The HP 48 lineup of graphing calculators, developed by Hewlett-Packard and available between 1990 and 2003, comprises the HP 48S, SX, G, GX, and G+ variants. The G series introduced additional capabilities beyond the S models, whereas the X suffix indicates support for memory expansion through RAM and ROM cards. Specifically, GX versions feature more internal memory compared to G models, while G+ units solely increase onboard storage. Notably, the SX and S share identical internal memory configurations.

Although similarly named, the hp 48gII released in 2004 does not belong to this series; it is instead closely linked to the HP 49g+.

These calculators operate using Reverse Polish Notation (RPN) alongside the RPL programming language. The hardware design of the HP 48 served as a foundation for later models such as the HP 38G, which simplified user interaction by adopting infix notation, and the HP 49G, which introduced enhanced software features. This design lineage traces back to earlier HP calculators like the HP-18C and the HP-28 series, illustrating a deliberate progression in HP’s programmable calculator development.

Models / Availability

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

Availability timeline:

HP 48SX: 1990 to 1993
HP 48S: 1991 to 1993
HP 48GX (F1895A): 1993 to 2003
HP 48GX ASEE Edition: Released in 1993 as a special model marked "1893 ASEE 1993 Shaping our world - Century II"
HP 48G: Available from 1993 until 2003
HP 48G+ (F1630A, F1894A): Produced between 1998 and 2003

Specifications

The HP 48 series is powered by the Saturn microprocessor, a hybrid CPU combining 64-bit and 20-bit elements that processes data and addresses in nibble units. Primary registers A, B, C, D, along with temporary registers R0 through R4, operate at full 64-bit width; data registers D0 and D1 are implemented as 20-bit. External data accesses are handled as physical byte (8-bit) transactions. Although the processor has a logical address bus width of 20 bits, only 19 bits are externally accessible due to nibble-level selection.

Both the HP 48S/SX and G/GX incorporate the Saturn core within complex integrated circuit packages named after figures from the Lewis and Clark Expedition: Clarke designates the S/SX models (after William Clark), while Yorke refers to G/GX variants (named after Clark’s servant). Earlier versions of Saturn ICs were labeled Lewis in honor of Meriwether Lewis.

Common features across all models

Processor architecture: Saturn
Display resolution: 131 by 64 pixels with three different LCD types enhancing readability
Connectivity options: RS-232 port using a 4-pin connector supporting UART communication at speeds ranging from 1200 to 9600 baud with parity settings; also includes an Infrared port (not compliant with IrDA standards)
External data bus width: 8 bits
Logical address space: up to 20 bits (equivalent to a maximum of 512 KB)
Register size capacity: up to 64 bits for both working and temporary registers
Expansion capability on X models: two card slots each with a 40-pin interface

Specifications unique to HP 48S/HP 48SX

Processor clock speed: runs at 2 MHz
Memory clock speed: also operates at 2 MHz
CPU codename: Clarke based on Saturn HP model 1LT8 core
Communication protocol supported: Kermit
Internal ROM capacity: 256 KB
Internal RAM size: 32 KB
Maximum expandable card memory supported: up to128 KB (exclusive to the SX model)
Released ROM versions include: A, B, C, D, E, F, J
Shift keys color-coded in orange and blue

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

Processor clock speed: ranges from 3.68 to 4 MHz
- Initial production runs yielded CPUs operating around 3.93–3.94 MHz for expandable variants (GX), with slightly reduced speeds for the non-expandable version (G); subsequent manufacturing improvements enabled all models to approach 4 MHz
- Frequency variation due to temperature changes is negligible
Memory clock speed: 2 MHz
Processor codename: Yorke (based on the Saturn architecture)
Supported communication standards: Kermit (protocol), Xmodem
Internal ROM capacity: 512 KB
Internal RAM size: 32 KB in the 48G, and 128 KB in the 48G+ and 48GX models
Memory expansion capabilities: up to 128 KB via port 1 and up to 4 MB through port 2 (with bank switching enabling addressing of 128 KB segments)
Available ROM versions include: K, L, M, P, and R
Shift keys are colored purple and blue-green, which may pose challenges for users with red-green color vision deficiencies

Programming

The HP 48 series employs a stack-oriented language known as RPL, which integrates elements of Reverse Polish notation and Lisp. This language supports passing and returning unevaluated expressions within its stack-based environment.

Two variants of RPL exist: User RPL, which can be programmed directly on the device, and System RPL, which requires compilation through external tools provided either by HP or third parties. While User RPL limits command usage to maintain system integrity and operates at slower speeds, System RPL offers access to low-level functions but carries a higher risk of causing system crashes if improperly used.

Additionally, assembly programming is supported on the HP 48 series using the HP Saturn assembly language. Developers can write assembly code using on-device utilities such as Jazz or utilize external assemblers like SASM, including official Hewlett-Packard compilers.

Emulators

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

In popular culture

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

External links