ZRAMZERO CAPACITOR RANDOM

ACCESS MEMORY

DRAM

Each bitcell requires 1 transisitor and 1 capacitor.

Needs to be refreshed every milliseconds to retain data because the charge of the capacitor leaks.

Memory density is less.

SRAM

Each cell which can store a single bit requires 6 transistors.

Does not need to be refreshed periodically as ip op retains the data

Faster access time compared to DRAM, therefore used as caches mostly.

Very less memory density.

UPCOMING TECHNOLOGIES

THYRISTOR RANDOM ACCESS MEMORY Combined strengths of SRAM and DRAM. Use Thyristor instead of Transistor.

TWIN TRANSISTOR RANDOM ACCESS MEMORY

Use transistor instead of capacitor. SOI tecnology based.

ZRAM

Its a hybrid RAM having the qualities of SRAM combined with the chip density of DRAM.

It uses a transistor (same as DRAM) but does not need a capacitor to store charge.

Its the cheapest RAM as it uses just a transistor and no additional circuitry.

Its fabrication is easier. High memory density.

Structure of ZRAM

Writing ‘1’ and ‘0’

Fabrication of ZRAM

Silicon on insulator technology (SOI) refers to the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates in semiconductor manufacturing

Speeds up the circuit by 30% As transistors shrink there is increase in

leakage current,the insulator blocks this leakage current.

System-on-a-chip or system on chip (SoC or SOC) refers to integrating all components of a computer or other electronic system into a single integrated circuit (chip)

COMPARISON

ADVANTAGES

ZRAM read/write performance is far better than conventional DRAM

ZRAM is twice as dense as conventional DRAM and about 5 times denser than SRAM

Its fabrication is quite simple Soft Error Rate is comparatively lower in

ZRAM. Lower power consumption Lithography friendly

DISADVANTAGES

It isn't fast enough to replace SRAM in L1 cache

SOI substrate is costlier to be implemented

Requires a large investment in new fabrication

Same latency as DRAM. Latency is the delay incurred when a

System tries to access data from memory Z-RAM is still a volatile memory

Is ZRAM really coming??

Isi is working with Hynix semiconductors to manufacture memory modules commercially.

AMD has started implementing ZRAM in there processors.

In the new design, the transistors are aligned vertically so that the gates are on either side and the junctions are at top and bottom

This provides the same isolation and same floating body effect.

THANK YOU