UMA is used in Silicon Graphics computers, and Phase 5 intends to use this high-end solution for the A\Box too. To get more information about the big benefits of the UMA, we recommend that you look at Phase 5's explanation. Their examples are good.

The Memory
When it comes to memory, the A\Box really shows power. It has 8 slots for 168-pins SDRAM, so it can fit a total of 1 GB (1024 MB) of RAM which is much more than a standard PC can handle. The 168 pins SDRAM is the new RAM standard which will replace the 72-pins EDO and FP RAM. Some of the latest PC's are shipped with SDRAM but since the memory-bus of the PC is so slow, the PCs can not make any good use of the SDRAM.

Speedrelations:
(the smaller the better)

• 168 pins SDRAM : 12 ns
• 72 pins EDORAM : 50 ns

SDRAM Frequently Asked Questions

What is Synchronous DRAM (SDRAM) technology?
A DRAM technology that uses a clock to synchronize signal input and output on a memory chip. The clock is coordinated with the CPU clock so the timing of the memory chips and the timing of the CPU are "in synch." A key feature of SDRAM is its ability to increase the overall system performance of the computer by reducing the time in executing commands and transmitting data. Specifically, it makes the implementation of control interfaces easier, and it makes column access time quicker. SDRAM includes an on-chip burst counter that can be used to increment column addresses for very fast burst accesses. To work with up to 100 MHz clock speeds, SDRAMs are designed with two internal banks. This allows one bank to get ready for access while the other bank is being accessed. This means that SDRAM allows new memory accesses to be initiated before the preceding access has been completed.

SDRAMs work differently from Fast Page Mode (FPM) and Extended data out (EDO) DRAMs. Signal propagation delays, i.e., the time from when the input signals are applied to when the signals become valid, are the main speed consideration with FPM and EDO DRAMs; therefore, FPM and EDO DRAMs are measured in nanoseconds (ns). The clock is the main speed consideration with SDRAMs; therefore, SDRAMs are measured in megahertz (MHz).

SDRAM technology is relatively straightforward. However the module design is complex and requires specialized testing equipment and procedures to ensure compatibility. For example, areas of greatest concern in testing include timing and spice analysis.

Is the introduction of SDRAM technology a revolution or evolution in system performance?
An evolution. The relationship between a PC and its memory components is becoming ever more complex as chip vendors roll out new types of DRAMs and computer makers struggle to evolve the architecture of the PC. In the days of 286 machines, the memory speed far surpassed the speed of the machine (CPU). With the introduction of faster machine speeds -- Pentium, 486, etc. -- the relationship between system requirements and DRAM capabilities clearly showed opportunities for new, faster DRAM architectures.

The evolution began with Fast Page Mode (FPM), moving to Extended data out (EDO) devices in 1995. These memory technologies are nearing the end of their product life cycle.

Some people have said that twenty percent of desktop computing systems will be shipping with SDRAM capability by the end of the year. And seventy percent of systems shipping with SDRAM by the end of 1997.

The 5 to 10 percent performance gain that SDRAM delivers over EDO on the standard benchmarks will be significantly increased -- 25 to 30 percent -- as systems begin to utilize their 100 MHz bandwidth capacity. Currently most systems are limited to a 66 MHz or lower bus speed.

What will be the next new memory technology and when will that become prevalent?
The performance of SDRAM will not be maximized until machines are functioning at 200 MHz. To support speeds in excess of 200 MHz , computing systems will require a significant re-design which would encompass areas such as packaging, interconnections, emissions and timing.

There are other memory technologies available today such as Rambus (RDRAM) and Sync-link. However, due to cost and major system restructuring these new technologies will not be introduced into the mainstream in the near future.

What will the cost difference be between EDO and SDRAM? Availability?
Currently, SDRAM chips are five percent higher than EDO with no supply issues. In the first quarter of ‘97 the price will come into parity. However, SDRAM modules will cost more due to additional engineering time and testing equipment to ensure compatibility. Furthermore, a complete computing system may cost more due to the technology and engineering expertise required to reach the 200 MHz capacity.

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