Real Calc vs Emulator - My Experience

[Christoph Giesselink]

As maintainer of emulators Emu28, Emu42, Emu48, Emu71 and V41 it's clear, I'm using emulators instead of the real calculator.

This is a story old days, so when you're not interested stop reading...

But what was my motivation to maintain Emu48 end of the 90'ies as first emulator?

Around 1994, 1995 I got the Horn Disk 4 with the HPTOOLS package allowing me to program my HP48SX in SystemRPL and Saturn assembler.

First I used my HP48SX with 2 128KB RAM memory cards, one to expand main memory filled with ~110KB of programs and data, the 2nd write protected filled with libraries for program development.

But when writing code in SysRPL or assembler it's only a function of time that you made a mistake and you get a memory loss and more worse you corrupted the user memory and don't recognize this. So after every programming session I restored the ~110KB of user memory with a backup copy. With the Kermit protocol this process took about 30 min. Later I put a XModem receiver program on the write protected memory card, and restoring the backup took about 3-4 min over XModem.

So in 1994, 1995 there was the wish having a system where it's possible to restore the user memory of the HP48 immediately with a mouse click. The system has a name, called emulator or simulator. At this time I found x48 0.4.0 in the Internet, a source code package of an emulator for the HP48SX and GX running on a Unix OS. 1994 and a Unix derivative? I'm not Rockefeller. So I bought a S.u.S.E. Linux distribution in 1994 with Kernel version around 1.0. First job were minor modifications on the makefile to compile and execute the x48 0.4.0 sources on this Linux distribution.

x48 0.4.0 at this time already emulated the serial port so in was possible to load programs over Kermit from local host or over a Null-Modem cable over RS232C from a different PC. So my first "professional" SysRPL development platform consists of two PC's, one running x48 on Linux, the 2nd a DOS PC with Editor and HPTools compiler and a Kermit client. Both PC's were connected over a Null-Modem cable. So I wrote and compiled the HP SysRPL programs on the DOS PC and transferred them with Kermit to the x48 emulator on Linux. Then I tested the program on x48 and was glad not restore my real calculator after such a debug session.

Things changed in 1997, meanwhile I had Windows NT4.0 and a found the freeware Emu48 v0.99.1 from May 1997. But Emu48 v0.99.1 was too bad for running it on NT4.0, so no further progress. In August 1997 with publishing Emu48 v1.0 as binary and source code everything changed. Because of the source code it was possible to fix the bugs in Emu48 to run this emulator on Win NT4.0 with less problems. So the idea, fixing the bugs in just one or two month, and then enjoy the HP48 programming/debugging in SysRPL and Saturn assembler with editor, compiler, emulator just on the same PC. As I told you, this was the plan with the focus on the HP48 program development and not working and spend time on Emu48 over decades.

So what has this to do with Emu42 and all later emulators?

Let my answer this question in the famous words of George Mallory. On the question "Why did you want to climb Mount Everest?" he answered "Because it's there". In my words, I was able and had the knowledge to write an emulator for the HP42S, so I done it. There was never the question, "Could I replace the usage of real HP42S calculator with an emulation on the PC?" Also the next calculator emulation in Emu42, the HP28S in 2002 some month later, was a question of nostalgia. I had a HP28S from 1988 to 1991, so I wrote the HP28S emulation and filled the user memory with all the programs at had used in 1991 saved as raw print files on disk.

At this time in 2000+ I always carried a real HP15C with me in my jacket. Because the HP15C becoming very expensive on the following years, I replaced the 15C in the jacked pocket by a HP32SII, a HP32S and finally by a DM15C.

At the moment I carry no calculator or a smart-phone with me. The only calculator I have on the way, is the original calculator program of a > 10 years old Nokia phone.

When I need a calculator at home or at work, I use my HP48SX emulation on Emu48 with all of the 110KB data I talked above (just restored the backup in the HP48SX emulation) on the desktop PC.

What is the fascinating part of pocked calculator emulators for me?

My first answer is the speed. Have a look on Erik Ehrling's "Miller-Rabin Primality Test for the HP-42S" with Prime number: 999,999,999,961

Some results:

Real HP-42S

ROM REV A: Std clock 1MHz 5m 48s
ROM REV A: Dbl clock 2MHz 2m 52s

2x E5507/2.26GHz/800MHz/DDR3 / 4 GB / Windows 7 SP1 (x86) / Emu42 v1.14

ROM REV C: Max 2s Auth 5m 25s

ARM PXA310/640MHz / Win Mobile 6 Classic / Emu42PPC v1.10

ROM REV C: Max 17s Auth 5m 26s

Samsung Smartphone M31 / Emu42 for Andriod v1.4

ROM REV C: Max <1s


When I had my HP48SX calculator last in hand? That's definitely some month ago checking the batteries for leakage.
Enjoy you calculator as original hardware or as emulation on external hardware, desktop, notebook or smart-phone, what ever you prefer...