HP 48G

HP 48 series
Company type	Product line
Industry	Electronics, Calculators
Founded	1990
Founder	Hewlett-Packard
Defunct	2003
Headquarters	Palo Alto, United States
Area served	Worldwide
Products	Graphing calculators (HP 48S, HP 48SX, HP 48G, HP 48GX, HP 48G+)
Owner	Hewlett-Packard

The HP 48 lineup, manufactured by Hewlett-Packard between 1990 and 2003, consists of sophisticated graphing calculator models such as the HP 48S, HP 48SX, HP 48G, HP 48GX, and HP 48G+. The G series models are upgraded variants of the S series, with the X suffix indicating support for memory expansion via RAM and ROM cards. Among these, the GX versions provide greater onboard memory than the G models, whereas the G+ models solely increase internal memory capacity. Both SX and S versions possess equal onboard memory.

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

These calculators employ Reverse Polish Notation (RPN) alongside the RPL programming language. The HP 48's hardware platform served as a basis for subsequent devices like the HP 38G, which introduced a more user-friendly interface and infix notation input, as well as the HP 49G, which featured enhanced software capabilities. The design of the HP 48 series itself was heavily influenced by earlier HP calculators including the HP-18C and HP-28 series.

Models / Availability

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

Availability timeline:

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

Specifications

The processors powering the HP 48 series are based on the Saturn microarchitecture—a hybrid CPU combining 64-bit and 20-bit operations with nibble-oriented data handling. The primary registers A, B, C, D along with temporary registers R0 through R4 have a width of 64 bits; meanwhile, data registers D0 and D1 are sized at 20 bits. Data retrieval externally is automatically translated into standard 8-bit accesses. Internally, the CPU uses a 20-bit address bus but effectively only accesses up to 19 bits externally due to nibble addressing.

For both the HP 48S/SX and G/GX variants, the Saturn processor is embedded within complex integrated circuits named after members of the Lewis and Clark Expedition: Clarke (used in S/SX models, named after William Clark) and Yorke (found in G/GX models, named after Clark’s servant York). Earlier Saturn ICs were designated Lewis.

Shared Features Across All Models

CPU type: Saturn architecture
Display resolution: 131×64 pixels; three different LCD versions were introduced over time to improve contrast and readability
Connectivity options: includes a 4-pin RS-232 serial port (UART supporting baud rates from 1200 to 9600 with parity settings) plus an Infrared port (using a proprietary protocol rather than IrDA)
External data bus width: 8 bits
Maximum nibble-based address range: up to 20 bits
Logical address capacity: up to 512 KB
Largest register size: supports up to 64 bits
Expansion card slots on X models: two ports available
Pins per expansion card connector: forty

HP 48S / HP 48SX Specific Details

Processor clock speed: runs at 2 MHz
Memory clock speed: also operates at 2 MHz
CPU codename: Clarke (Saturn core designated HP 1LT8)
Supported communication protocol(s): Kermit protocol
Internal ROM capacity: contains 256 KB of read-only memory
Internal RAM size: equipped with 32 KB of random access memory
Maximum expansion card memory supported: up to 128 KB (applicable only for the HP 48SX)
ROM firmware versions released include A, B, C, D, E, (F), and J
Features orange and blue shift keys for extended functionality

Specifications for HP 48G, HP 48GX, and HP 48G+

Processor clock speed: ranges from 3.68 up to 4 MHz
- Initial production batches categorized CPUs near 3.93–3.94 MHz for expandable variants (GX), with slightly reduced speeds for non-expandable models (G); subsequent manufacturing improvements enabled nearly 4 MHz processors across all versions.
Memory clock speed: 2 MHz
CPU codename: Yorke (Saturn architecture)
Supported communication protocols: Kermit (protocol), Xmodem
Internal ROM capacity: 512 KB
Internal RAM size: 32 KB for 48G, and 128 KB for both 48G+ and 48GX
Memory expansion capability: up to 128 KB via port 1, and up to 4 MB through port 2 (with 128 KB accessible through bank switching)
Available ROM versions: K, L, M, P, R
Shift keys colored in purple and teal—a design choice that poses challenges for individuals with red-green color vision deficiency

Programming

The HP 48 series utilizes RPL, a stack-oriented programming language that merges Reverse Polish notation with elements of Lisp, enhancing stack manipulation by incorporating lists and functional constructs. This language supports passing code segments unevaluated as function parameters or returning them by leaving them on the stack.

There are two variants of RPL: User RPL, which can be coded directly on the calculator offering safe argument validation but with reduced execution speed, and System RPL, which requires external compilation, provides more granular control over operations but carries a higher risk of system crashes if improperly used.

Moreover, assembly programming for the HP Saturn processor is feasible using either third-party development tools or official HP software, allowing users to achieve advanced customization and optimize performance.

Emulators

Emu48 – Windows platform
Alcuin – Commodore Amiga system
X48 – Mac OS X and POSIX-compliant systems (Unix/Linux)
i48 – iOS emulator for HP48GX based on X48
m48 – iPhone emulator for HP48 derived from Emu48
Droid48 – Android emulator for HP48G built on X48
droid48sx – Android emulator for HP48SX 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 is featured in the 2012 movie The Amazing Spider-Man as well as its sequel.

External links