Write-only memory (engineering)

In data innovation, a compose just memory (WOM) is a memory area or enlist that can be composed to however not perused. Notwithstanding its exacting importance, the term might be connected to a circumstance when the information composed by one circuit can be perused just by other hardware. The most well-known event of the last circumstance is the point at which a processor composes information to a compose just enroll of equipment the processor is controlling. The equipment can read the direction however the processor can't. This can prompt issues in delivering gadget drivers for the equipment.

Compose just recollections additionally discover applications in security and cryptography as a methods for counteracting information being captured as it is being decrypted.In 1972, WOM, a direct opposite of read-just memory (ROM), was presented as an inside down to earth joke executed by Signetics.[1] Anyway, it was soon perceived that this idea really portrays certain functionalities in chip systems.[2]

The most incessant events of compose just recollections are the place the memory areas are registers or an incorporated circuit being utilized to control, or pass data to, equipment outside the processor. A focal handling unit (CPU) can keep in touch with these areas, and in this manner control the equipment, however can't read back the data and find the present condition of the equipment. The memory is compose just relative just to the CPU's perspective. Such game plans are normal on little inserted microcontroller frameworks to spare expenses and can bring about troubles for writers of gadget driver software.[3] When the momentum equipment state is obscure to the CPU it can just place it into a known state by sending another order, which may bring about the state changing.[4] To reduce this trouble, the substance of the WOM might be reflected by the CPU in the customary memory.[5] Be that as it may, this system is just dependable if the enroll is perused just from the point of view of the equipment.

A case of this sort of utilization concerned access to memory on early PCs. The first PCs utilized 8086 or 8088 processors which had the capacity to address just 1 MB of memory. An extensive piece of this was involved by the Profiles bringing about just 640 kB of addressable Slam being accessible. The memory prerequisite of numerous applications soon outperformed this figure. One strategy for conquering the confinement was by the utilization of bank-exchanged Smash. Various banks of Slam are given, however are not for all time doled out to a memory area. In a specific usage, an exceptional board is added to a PC, which controls the designation of banks to memory space. The control board has its own particular memory chip. A PC can compose information into this chip, yet just the control board itself can read the chip, consequently it is named "compose just" memory.[6]

Another illustration concerns a few capacities done by representation handling units (GPUs). For example, a GPU may complete shader preparing on the substance of representation memory. It can be quicker and more proficient for the GPU to take enter for the shader procedure from read-just areas and compose the shader yield to various compose just areas without copying information between the read and compose cushions after each iteration.[7]

An illustration that is still of contemporary significance can be found in the 16550 UART, whose subordinates are still in broad utilize. To include an information FIFO without breaking similarity with the 8250 UART's 8 arrangement enrolls, the compose just "FIFO control enlist" was doled out an indistinguishable port address from the read-just "interfere with recognizable proof enlist". Keeps in touch with that address program the FIFO control enroll, however there is no real way to peruse it back.

The term is additionally used to portray the PC perspective of certain show gadgets, for example, the e-ink screens utilized as a part of e-readers.[8]

Security and encryption[edit]

Locking the edge cradle of a GPU to adequately transform it into a compose no one but memory can be helpful in ensuring encoded information. At the point when scrambled information lands at its goal, it should be unscrambled before it can be shown to the client. The presence of decoded material in memory where it can be gotten to by the CPU or fringe gadgets is a potential security shortcoming. This shortcoming might be eased via completing the decoding inside the GPU and composing the decoded information straightforwardly to show memory. Nothing else can read the information while the edge cradle is bolted, and when it is opened it will show something else.[9] All current shrewd cards that component a chip can likewise be said to depend on WOM innovation, since they are customized at a processing plant with certain encryption scratches that can not specifically be perused by a card peruser. Rather the keys are in a roundabout way utilized by calculations that approve passwords or decode certain substance.

Calculability theory[edit]

In calculability hypothesis, adding a WOM to a few models of calculation can build their computational power.

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