SGRAM stands for Synchronous Graphics Random Access Memory. It is a type of DRAM, generally used for video memory. SGRAM is clock-synchronized, just like DRAM.
The earliest known SGRAM memory was introduced in November 1994, by Hitachi, the HM5283206. Later the NEC µPD481850 was introduced in December 1994.HM5283206, an 8M-bit synchronous graphic RAM (SGRAM), offered an operating speed of 125 MHz, as high-speed image processing memory for use in PCs, engineering workstations, TV game players, and similar devices. The data transfer speed of HM5283206 was 500 Mbytes per second.
Characteristics of SGRAM
- Single-Ported: SGRAM is single-ported. However, it can open two memory pages at once, which simulates the dual-port nature of other video RAM technologies.
- Cost-efficient: It is relatively low-cost video memory RAM when compared to alternatives like GDDR. It was widely used by Flash Web Designs companies
- Clock-synchronized: Like SDRAM, SGRAM can also synchronize by cloak. It is capable of synchronizing with a CPU bus at speeds of 83 MHz, 100 MHz, 125 MHz, and 142 MHz.
- Masked Write: This function allows the selected data to be modified in a single operation instead of a sequence of read, update, and write operations. The bit-masking function allows writing to a specific bit of plane, not affecting the others.
- Block Write: This function allows data for image fills to be handled more efficiently(filling a block of memory with a single colour).
Advantages of SGRAM
- SGRAM run at a very high speed making them suitable for 3D Graphics and Games.They can have clock frequencies up to 200 MHz coupled with CAS Latency 2 performance of 143 MHz and single cycle block write.
- The chips provide a high bandwidth ranging from 572 Mbytes/s at 143 MHz to 667 Mbytes/s at 167 MHz.
- Higher data transfer rate and I/O width per channel is 32/16 or 16/8
Disadvantages of SGRAM
- SGRAM is less temperature resistant than SDRAM. It cannot withhold a range of temperature.
- Unlike SGRAM, SDRAM variant can transfer data both on the raising and on the falling signal edge.
- SGRAM, even though having a good range of bandwidth, cannot compete with DDR with bandwidth of 12.8GB/s