On ode to the -41CL; Sometimes its the little things...


It has been about 9 weeks since I first assembled my SY-41CL. My HP-41CX has always been my favorite calculator since I bought it in May, 1984 as a college graduation present to myself to replace my HP-41CV. I have collected almost all the high end HP programmable scientific calculators since then (28S, 42S, 48GX, 49G, 50G, 35S, 15C LE) and have toyed around with most of them, but nothing was really ever able to replace my proficiency and comfort level with my 41CX.

That is... until I started to use my 41CL. This should not be a surprise, as the 41CL is pretty much a 41CX on massive amounts of steroids. The learning curve is pretty quick, and the extra capabilities are significant.

I take pauses away from my several hobbies now and then, and I was on pause as the 41CL was being developed and initially shipped. Some of what I have to say may be a repeat of others' observations, but I wanted to share my experiences in case it is of interest to others.

I think most people know about the 41CL's major claims to fame. Up to 50X execution speed, every ROM image known to man built inside its little brain, and RAM enough to create a hundred 'virtual' 41CX's. This is about the little things that I really appreciate about this precious gadget.

The SY-41CL is FAST! Why anyone would want to leave it in normal old, 1979 speed is beyond me. Monte warns of increased battery consumption and suggests that the only advantage is when running programs and therefore turbo mode should be used conservatively, but he is wrong! The battery use outside of program mode is not signficantly more than at normal speed, and there is good reason to leave it on all the time. Here are the little things that really make me smile.

Make a mistake spelling out a function? On the original 41, even lightly loaded with external roms, I'd have to wait a second or two for the device to figure out I was a bonehead, during which time, already knowing it, I'd just have to wait for "NONEXISTENT". A fully virtual-port-loaded -41CL returns "NONEXISTENT" instantaneously. No waiting! I can get on with correcting my problem and moving forward immediately.

Closely related, when I am not being a bonehead and actually spell the function properly, there is NO wait time for the 41CL to find it and begin executing it in Turbo mode. Even deep into catalog 3 with a full suite of Catalog 2 ROM entries in the way. Very nice! I hate waiting.

User mode is much more friendly. With the old 41CX, if User Mode was on, and the program counter positioned in a long user code program in ROM or RAM, pressing the top two key rows would result in a local label search that would slow my progress down quite a bit. The alternative was to turn off USER mode for a key stroke, and then have to turn it back on later. I remember seeing the suggestion years ago that a user might consider making key assignments of the normal printed functions on these keys in order to resolve this issue! Ridiculous! With the -41CL however, there is no wait. Even in long programs (> 1000 lines) the local label search takes only a fraction of a second. I now can leave the 41CL in USER mode all the time without having to wait for it to look for something it is not even going to find.

Going into program mode? No delay! The 41CL counts the number of unused registers instantaneously for display, without having to wait. Program editing is fast. There is no wait time to insert lines into programs, jump to specific line numbers, and that nasty delay while a decompile is done when exiting program mode after editing a long program is gone. PACKING? For a 1131 line program, it takes maybe 1/2 of a second to finish. Changing the SIZE? Instantaneous!

And of course, there is program execution. Blazingly fast. Programs that used to take over 10 seconds to deliver a result now take less than a half of a second!

Back in 1988 I bought a 2X speed upgrade kit for my HP-41CX. It was nice. But, I did have to live with some issues. The BEEP and all TONEs were sped up in both duration and pitch. Catalogs would go by too fast to read easily. I had to be particular about what modules were plugged into the calculator when it was running in Turbo mode. Not everything played well at a 2X bus speed, especially my triple (Advantage, 2 X-mems) module. Monte solved all that. The 41CL catalogs run at near normal speed (Cat 2 'header catalog' runs a little faster), tones and the beep are as designed, and best of all, all port devices work just fine.

Having an engineer/geek nature, I tend to have close relationships to my devices. The SY-41CL has become a good friend. A very good friend indeed.

Edited: 6 Mar 2013, 3:44 p.m.


Very kind words, Dan. Thank you. As you probably deduced, the CAT display is a little faster for the same reason that everything else is fast: it takes much less time to search the FATs in a Turbo mode.

The 41 has been, and always will be my "go to" calculator, and that was half of the reason for the CL project. The other half was that more than one person (many actually) said that it couldn't be done.




I received on Friday your circuit, and installed it on one of my '41. Let me tell you that the aspect of the circuit is excellent, the fit in the machine perfect, and it worked flawlessly from the start.

A New Calculator is born

I now need to make up my mind on which are the modules that will be loaded as standard. Probably I will do as some here: keep several sets that can be switched with a small program.

The first I have loaded is the Advantage pac - but I have not made up my mind with the rest.

The calculator used the infrared module without any problem, first time. "TRACE" function works well.

I now need to find a Time Module (and be able to retire my CX from daily use 100%)


Jose, thank you for the kind words, and cool blog post. As far as which modules to load, take a look at the PowerCL image. It requires a library to be loaded into Page 4 (the manual is on the Systemyde website), but makes the CL much more user-friendly.

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