HP 48S

HP 48
Company type	Product line
Industry	Consumer electronics
Predecessor	HP-18C, HP-28 series
Founded	1990
Defunct	2003
Fate	Discontinued
Successor	HP 49g+
Owner	Hewlett-Packard

The HP 48 line of graphing calculators was manufactured by Hewlett-Packard from 1990 until 2003. This lineup comprises the HP 48S, HP 48SX, HP 48G, HP 48GX, and HP 48G+ variants. The G models present enhanced capabilities compared to the S versions, while those marked with an X suffix support memory expansion through RAM and ROM cards. GX models feature greater built-in memory than the G series, whereas G+ versions increase onboard memory exclusively. Both SX and S models share identical onboard memory sizes.

Though similarly named, the hp 48gII released in 2004 is not part of this series but is closely associated with the HP 49g+.

These calculators operate using Reverse Polish Notation (RPN) and are programmed in the RPL language. The hardware framework of the HP 48 served as a basis for later devices such as the HP 38G, which introduced a more straightforward interface featuring infix notation, and the HP 49G, which included software advancements. The design lineage traces back to earlier Hewlett-Packard calculators, notably the HP-18C and the HP-28 series.

Models / Availability

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

Availability timeline:

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

Specifications

The HP 48 series is powered by the Saturn microprocessor, a hybrid CPU combining a 64-bit and a 20-bit architecture 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, whereas data registers D0 and D1 are limited to 20 bits. External data retrievals are transparently converted into physical fetches of eight bits. Internally, the processor uses a 20-bit address bus; however, externally it is limited to 19 bits due to nibble selection constraints.

Both the HP 48S/SX and G/GX series incorporate the Saturn processor within sophisticated integrated circuit packages named after members of the Lewis and Clark Expedition: the S/SX models utilize a package codenamed Clarke (after William Clark), while G/GX models use Yorke (named for Clark’s servant). Earlier Saturn ICs carried the codename Lewis.

Common features across all models

Processor architecture: Saturn
Display resolution: 131 by 64 pixels; three different LCD versions were introduced over time to enhance contrast and readability
Communication interfaces: standard RS-232 port with a four-pin connector supporting UART at baud rates from 1200 to 9600 with parity options, plus an infrared port employing pulse-based signaling (non-IrDA)
External data bus width: 8 bits
Maximum address bus width: 20 bits (organized in four-bit cells)
Logical addressable memory space: up to 512 KB
Largest register size: full 64 bits
Expansion card slots available on X models: two
Pins per expansion card slot: forty

Specifications specific to HP 48S/HP 48SX

Processor clock speed: 2 MHz
Memory clock speed: also running at 2 MHz
CPU codename: Clarke (Saturn HP1LT8 core)
Supported communication protocols include Kermit
Internal ROM capacity: 256 KB
Internal RAM capacity: 32 KB
Maximum memory expansion per card (only on the SX model): up to 128 KB
ROM firmware revisions identified as A, B, C, D, E, (F), J
Distinctive orange and blue shift keys

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

Processor clock speed: ranges from 3.68 up to 4 MHz
- Initial production batches sorted CPUs into performance categories: higher-frequency (~3.93–3.94 MHz) chips were allocated to the expandable GX models, while lower-frequency versions were used in the non-expandable G variants; subsequent manufacturing improvements allowed nearly 4 MHz CPUs to be installed across all models
Memory bus speed: 2 MHz
CPU code name: Yorke (based on the Saturn architecture)
Supported communication standards: Kermit (protocol), Xmodem
Internal ROM capacity: 512 KB
Built-in RAM size: 32 KB for the 48G, and 128 KB for both 48G+ and 48GX models
Expansion memory capability: up to 128 KB via port 1, and up to 4 MB through bank-switched port 2
Firmware versions include: K, L, M, P, R
Shift keys are marked in purple and blue-green hues, which may present challenges for individuals with red-green color vision deficiency

Programming

The HP 48 series utilizes a stack-oriented programming language known as RPL, which integrates principles from Reverse Polish notation and the Lisp family. RPL allows unevaluated code fragments to be passed and returned on the stack, offering enhanced programming versatility.

RPL exists in two variants: User RPL and System RPL. User RPL can be programmed directly on the calculator itself and restricts hazardous commands to prevent crashes, though it executes more slowly. Conversely, System RPL requires compilation via either third-party tools or HP’s official compiler; it provides access to lower-level functions but carries a higher risk of system instability if improperly used.

Moreover, the HP 48 supports assembly language programming for the HP Saturn processor through on-device utilities such as Jazz or external software like SASM, enabling advanced users to tailor performance and functionality extensively.

Emulators

Emu48 – Windows platform emulator
Alcuin – emulator for Commodore Amiga systems
X48 – compatible with Mac OS X and POSIX-compliant Unix/Linux systems
i48 – HP48GX emulator for iOS devices built upon X48
m48 – iPhone emulator for HP48 based on Emu48
Droid48 – Android emulator for HP48G derived from 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