While comparing the system speed rates, very few advantages can be seen for 75 Mhz (101 percent) and 83 Mhz (100 percent) as a result of impractical multipliers. Users are advised not to goo for such mother boards with such strange bus speeds. It is wiser to get a 100 Mhz board. The clear increase in the system speed does not seem to effectively outdo the small reduction in the processor speed. On an average the difference are too small to allow one to judge the operational consequences.
RAM POWER
In contrast with Fast Page Mode DRAM (FPM DRAM) Extended Data Out DRAM (EDO DRAM) does not simultaneously use control line (pilot wire) CAS (column Address Strobe) as an indicator for a valid fitting column address and as signal for valid readable data. The data thereby remains readable, while the next column address is transmitted. The time window for the memory access diminished and the average increases.
The synchronous DRAM (SDRAM) principally uses the same memory location, but does not have additional logic for optimization of Burst Accesses. i.e. for the transfer of data on the subsequent memory locations. With this the SDRAM itself generates the addressing for the following memory locations after triggering a Burst -access through the RAM-controller. This happens synchronous to a speed signal, in a normal case synchronous to the system-speed, with one signal per delivered date.
A typical Burst-Access with four consequent addresses require only 5-1-1-1 signal, in a ideal case. EDO-DRAM on the contrary, brings this to a 4-2-2-2 cycle.
The SDRAM for 100 Mhz is already available, whereas EDO-DRAM would get exhausted at 75 Mhz. The deciding SDRAM-parameters, the cycle time in the Burst-Mode is specified on the chip. '10' for 10 nano seconds that correspond to a speed of 100Mhz can be seen. The speed specifications in case of FPM or EDO DRAMs on the contrary, represents the RAS - access time, I.E. the time which is spent between creating the line-addresses up to the preparation of the valid data, typically '60' for 60 nano-seconds.
Tip: Good DIMM-modules contain an additional tiny EPROM in which the manufacturer stores important Timing Parameters apart from the RAM -chips. Through this, a Board chipset can ideally adjust to every module. The RAM -controller needs no advice. Chipsets like 440LX from intel actually make the parameter-Memory a prerequisite.
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