Reason for Voyager LCD colors

[mdanoregon]

Hi,

I have several 12c calculators and noticed the LCD has different colors.

A couple prior to 1986 have a grey LCD.

Others made after 1986 have a yellowish LCD.

Two Platinum's have a grey LCD and a recent calculator made in China has a yellowish LCD so it seems the color choice is intentional.

Next to each other, the difference is noticeable.

Would anyone know the cause or reason for this?

Is it possible the grey to yellow LCD change around 1987 corresponded to chip changes?

In the image, the calculators are from 1982, 1986, and 1988 with the one from 1988 having the yellow display.

[brouhaha]

There were some LCD changes that were not accompanied by other circuitry changes, probably before 1988. The circuitry changes going from the 2:1 mux display to a higher mux ratio appeared with some of the SST chip variants (1LQ9 in 1988, 1RR2, 2AF1, and Atmel ARM).

AFAIK, all of the 2:1 LCDs are interchangeable. The 4:1 non-ARM.might be, but the 2005+ 4:1 ARM.probably aren't interchangeable with the 4:1 pre-ARM.

YMMV.

[mdanoregon]

Hi,

Thank you.

The 1988 date on the 1LQ9 chip is really helpful since I have been wondering about this.

I saw a youtube video where the person speaking said they liked the older HP 15c's because they used sapphire when making the chips.

Are there dates on when HP stopped using this process or on what chips?

I'm curious if the voyagers prior to the 1LQ9 chips were made using sapphire.

[Steve Simpkin]

(01-11-2024 05:55 PM)mdanoregon Wrote:  Hi,

Thank you.

The 1988 date on the 1LQ9 chip is really helpful since I have been wondering about this.

I saw a youtube video where the person speaking said they liked the older HP 15c's because they used sapphire when making the chips.

Are there dates on when HP stopped using this process or on what chips?

I'm curious if the voyagers prior to the 1LQ9 chips were made using sapphire.

It has been a common misconception that the original Voyagers calculators used a Silicon-on-Sapphire process which was responsible for its extremely low power consumption. In fact HP used a custom CMOSC process. This is explained in detail in the Jan 1983 issue of HP Journal magazine (page 23).
https://www.hpl.hp.com/hpjournal/pdfs/Is...983-01.pdf

[brouhaha]

(01-11-2024 05:55 PM)mdanoregon Wrote:  I saw a youtube video where the person speaking said they liked the older HP 15c's because they used sapphire when making the chips.

Unfortunately that is widely spread misinformation. HP didn't use any silicon-on-sapphire (SOS) for chips for small calculators. They had used SOS in some of the "big" machines in the 98xx series for HP-IB interface chips and such. SOS was vey expensive, and the 98xx machines were not cost-sensitive. All of the "small" HP calculators (handheld calculators and related small desktop calculators such as the, 46, 81, 91, 92, 97, 97S) were far more cost-sensitive (despite seeming expensive to us customers). None of the small calculators used the expensive SOS process. If HP continued making any SOS chips beyond that timeframe, it's news to me. The only applications SOS is normally used in since then is military and space products, because SOS is inherently radiation-tolerant, while bulk CMOS has to be subjected to a "radiation hardening" process for space applications. No normal consumer, commercial, or even industrial applications justify the expense of SOS.

The earliest that HP used CMOS in small calculators was the 25C. They initially used CMOS chips made to HP requirements by outside vendors, and those were made using conventional CMOS technology similar to the original RCA CD4000 series CMOS chips. They brought CMOS design in-house a little later. The use of CMOS chips in the HP-41C was documented as "bulk CMOS" (the regular kind, vs. SOS) in an HP Journal article, which also mentioned how they had set up their own fab line for bulk CMOS, and used it for their previous generations of continuous-memory calculators.

Bulk CMOS fabricated by HP went on to be used in the Voyager calculators, and all subsequent small HP calculators. The Voyager calculators initially used basically the same CMOS process as the 41C, but later in the 41 and Voyager product cycles, they used newer, finer-geometry CMOS, which is how they got 120Kbit ROMs for the 41CX and 12K ROM modules, and the 1LQ9 SST chip for the Voyagers.

For the 48G/GX and later versions of Pioneer calculators, they started using bulk CMOS semi-custom gate arrays facbricated by NEC rather than in-house fabrication. These might have had the customization designed by HP using NEC-provided CAD tools, or that might have been done by NEC to HP-provided specifications. That was the last gasp of HP using either full-custom or semi-custom silicon in calculators.

With the 49g+ and 50g, HP started using commodity microprocesors and microcontrollers for even the HP-designed calculators. These are all bulk CMOS. For the 49g+, 50g, and related models, they used Samsung ARM SoCs. The 12C Platinum used a SunPlus (now GeneralPlus) 6502 derivative (which is sometimes referred to as "8502", for no good reason). The 10bii+, 20b, 30b, and post-2004 12C and 15C use Atmel (now Microchip) ARM microcontrollers.

[mdanoregon]

The article and history on the chips is helpful and interesting.

I appreciate the guidance.