The NOR Flash-ROM was invented by Toshiba in 1984 and found its way immediately as a replacement of the more expensive ROM (NRE mask costs) and EEPROM (device costs) memory. The NOR Flash-ROMs use an address and data bus to allow the random access to any memory location. Main disadvantages of the NOR Flash-ROM compared to the NAND Flash-ROM are the higher costs, larger housings and slower write speeds.

The disassembled TI-Nspire ViewScreen Panel (Manufactured July 2007) makes use of one SST 39VF400A, manufactured by Silicon Storage Technology, Inc. with a 256k*16 bits organization.

The NAND Flash-ROM architecture was introduced by Toshiba in 1989 and is based on pages of typically 512 to 2048 Bytes and blocks of typical 32 or 64 pages.

While programming is performed on a page basis, erasure can only be performed on a block basis. NAND Flash-ROMs requires bad block management to be performed by device driver software or hardware. Due to the missing address bus the NAND Flash-ROM chip doesn't allow random access to the individual memory positions and therefore it can't be used for program memory of a microprocessor. Typical use of the NAND Flash-ROM is file based mass-memory storage such as memory cards.

The disassembled TI-Nspire ViewScreen Panel makes use of one ST NAND256W3A NAND Flash-ROM with 32M Bytes.

SDRAM is the abbreviation of synchronous dynamic random access memory and is used as program and data memory for microprocessor systems. Each bit of data in a SDRAM is stored in separate capacitor on the integrated circuit. Since these capacitors leak charge over time, the information eventually fades unless the capacitor charge is refreshed periodically.

Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory. Its advantage over SRAM is its structural simplicity: only one transistor and a capacitor are required per bit, compared to six transistors in SRAM. This allows SDRAM to reach very high density at low cost. Since SDRAM loses its data when the power supply is removed, it is accompanied usually by a NOR Flash-ROM.

During power-up of the system the program content of the NOR Flash-ROM is simply copied into the SDRAM and executed from there. We assume that the TI-Nspire uses the SDRAM as workspace for user data but stores changes on them into the NAND Flash-ROM.

The disassembled TI-Nspire ViewScreen Panel makes use of one Infinion HYB18L256160 SDRAM with 16M*16 bits size.

Please notice that all three memory chips are almost identical with the parts located in the released TI-Nspire CAS with an April 2007 manufacturing date. The only difference is the supply voltage, it was lowered from 3.3 volts to 1.8 volts.