Can anyone tell me about the "41CY"?


Hi all.

I am curious about the capabilities of the
"souped up" 41CV, the 41CY.

Can anyone enlighten me about the specs of these machines?
And who did the soup-up? How far did they go? When was it done?


Don W


The HP41 CY is basically an HP41CX with the guts of the W&W Rambox built inside. It was done by W&W in Germany. The RAMBOX electronics are on a custom PCB (actually just the memories and an Asic) that is mounted between the keyboard PCB and the bridge PCB in the 41CX. I had the opportunity of looking at the insides when I visited W&W earlier this year.

They are very very rare and if one is available on ebay the price is really high.



Hi Meindert!

Thanks for the response.

What are the specs? RAM size, etc...?


Don W


Hi Don,

the CY Turbo has 64K (2* 32K) RAM,

as well as a turbo switch for CPU clock speedup,

I think it was about 1.7x .

You can switch between the two 32K blocks via software.

There also existed a W&W HP-41CW,

which was a CV with a 32K RAM 'box' built-in.

The latter is even rarer than a CY.



BTW: Your module is on its way to you;-)


Hi Raymond,

Do you have either of these delightful creatures? :-)




Hi all. Thanks for your reply and looking forward to hacking
my module. You were really patient with me (busy and
disorganized at this end) and very easy to do business with. Thanks...
(I never knew international bank transfers were so expensive).

I am looking at building one or two of these (41CW)babies, Bill.
If you want one let me know. There's (quite) a bit of work (and reading) to do first...

BTW, does anyone know WHERE in the systems address space they stick a 32 kB block of RAM? And how do you access it from a system programming point of view? I am aware you can't use the "operating system" adddress pointer on the whole lot, as it's only 12 bits wide (giving 1024 registers maximum which can be "pointed to")?

Don W

Don Wallace



Sorry Raymond!

My previous post omitted: "Hi all. Hi Raymond."
Thanks for the precise informative reply, Ray.

Don W
(I am sometimes a bit "scattered" at 6:30 a.m. before I have my
SECOND CUP of coffee. My g/friends a shift worker :-)


Hi Don,

Quick answer is the W&W Rambox -- in its various versions -- simulates ROM Module memory so, by using a RAMbox you are giving up the ability to use ROM modules.

The "system memory" of the 41 consist of 16 4K x 12bit blocks: 0,1 & 2 are the main 12K system ROMS. Blocks 3 & 5 are reserved for the Time Module and the Extended Funcitons ROM (extended functions RAM registers are mapped into the "user" memory). Block 4 is special: it's designed to map a "takeover ROM" taking control from the OS ROMS.
Block 6 is used by the Printer ROMS and Block 7 for the HPIL ROM.
Finally Blocks 8-F are for "normal" ROMS.
In use the 32K Rambox maps over Blocks 8-F: 4k * 8blocks = 32K. The 64K Rambox is simply 2 banks of 32k which can be switched with custom code.

Of course, it's not quite that limiting--you could map out blocks of RAM to allow space for ROM modules, map RAM to system blocks 3,4,5,6 & 7,etc.

Take a look at Diago's Clonix/NoVRAM and Meindert's MLDL2000. The MLDL is the Rambox on rocket power thanks to modern high density chips (and Meindert's hard work)-- lots and lots of memory banks, very flexible mapping, the ability to load ROM module images -- think the entire 41 module library in a card reader case.


Thanks for the quick reply David.

Very interesting...

There certainly are a few talented people doing work in this area.
I like Meindert's effort and am amazed at what Diego has already done and what Monte is doing...

At the moment I am interested in doing a FORTH41 module and a
PPC module in one plug in ROMPACK. I am planning to use the quad flat pack version of a PIC chip which is backward compatible to
the chip Diego was using, an 18LF2520. I have some pictures on
my website, if anyone is curious.

Later I want to rewrite the code (if possible) to drop the
PIC clock speed and lower the power consumption. It will be a
while before I am ready to do that, though. I am far from sure
if it can be done. I like a challenge though.

Considering it's age, the 41 machine is very well designed.
I don't have any other HP calcs (or other gear), but I remember
when I first bought my CV in early 1981 it just mesmerized me...
I still get a kick out of playing with it and use it to do simple
project management using the TIME module I bought in 1985 from a guy who had upgraded to the CX, then brand new.

Since then my calculator has suffered some four different hardware failures, so I am not sure how much longer it will last, but it's an amazing, functional, beautiful relic from a bygone age.
I am certainly getting good at fixing them... ;-)

Don W



I do not know too many details about the Rambox operation. Probably the manuals are available on a DVD or downloadable from TOS. As I understand there are some possibilities with special key combinations, but I am not really certain. I think that the speed switching is with a key combination.
The MLDL2000 operates in a totally different way, module assigment is best done for the outside with the USB interface under control of a PC.



Hi Meindert.

Thanks for the reply. You are a bit of a wizard...

I forgot stick up my website url:

On the softwar side, I am really chuffed at Warren Furlows V41.
It is really cool!

Don W
P.S. Great forum you got here, guys...


I think that the speed switching is with a key combination.

Sorry that's wrong, It's a seperate red switch on the left side of the calculator.

Calculator speed changing is only allowed in calculator off state.




I think I also read something about switching speed via keyboard. If I am not wrong, it was the "W&W cursor" on TOS where I read it.


I think I also read something about switching speed via keyboard. If I am not wrong, it was the "W&W cursor" on TOS where I read it.

Maybe, the working CY Turbo I have seen, has the manual switch.

But there were other companies which sold speed doublers for the 41. W&W also sold the Turbo option for normal calculators. They maybe different from the CY one.

AFAIK all 48 speed doubler use a key combination at startup?




Overclocking the 41CV due to the generous margins in the basic design, is quite simple. A timing capacitor is reduced in value or another one is put in series, dropping the capactiance.

From memory, in 1982 I used a 47 pF capacitor in series with the original which roughly doubled the machine speed. Anyone interested can write to me for details. Shorting my added capacitor with some fine wire restored normal operation without resoldering anything.
I found the faster CAT display annoying and didn't need the extra speed anyway. I also disliked the "sped up beep" tone...

Switching a capcitor into and out of circuit while the oscillator is running (calc powered up) generates a timing glitch kind of similar to what grounded Columbias (first space shuttle) maiden flight, (for different reasons). This glitch could perhaps cause some odd behaviour in the (memory access performance of) system.

It is possible that a keystroke sequence allowed special hardware to switch an extra timing capacitor into and out of circuit, but with such glitches... Maybe the people who thought this up had trouble and went back to a hardware switch which worked when the calc was off? Anyone?




The TURBO switch is also mentioned in the German W&W CY/Rambox II manual, so the switch is original W&W.




From what I have read here the 48 speed doubler is a "software hack" so no hardware glitches...



Hi Don,

at least my HP-48GY+ Turbo uses a hardware pcb

to hold the speed-up electronics and the additional RAM.

The speed-up is activated by holding the ON key

for some seconds longer than normally needed.

Maybe you meant the HP-28S and the HP-42S where

you could temporarily speed up the machine

by poking a different delay value at a certain RAM location.




Hi Raymond. Yes you are right of course. My mistake.


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