Como a freqüência e a latência da RAM diferem? Como isso afeta o desempenho?

Question

Eu tenho uma pergunta sobre duas especificações de memória RAM, a quantidade de Mhz e os tempos de latência (exemplo: 9-9-9-24).

Qual dos dois é mais importante para o desempenho do sistema e por quê? Além disso, qual é exatamente a diferença entre os dois?

    

Answer 1

Um artigo da Toms Hardware faz um bom trabalho ao explicar os tempos de RAM

• CAS, usually expanded as column address strobe (or sometimes as column address select), which refers to the column for some physical memory location in an array composed of columns and rows of capacitors used in dynamic random access memory (DRAM) modules (of which all three types of RAM in this guide are sub-types). CAS latency generally appears first in timing sequences for RAM and indicates the number of clock cycles that elapse between when the memory controller instructs the memory module to access a particular column in its current row, and when such access produces the data that resides there.
• Trcd or tRCD, usually expanded as RAS to CAS delay, where RAS is expanded as row address strobe, where R refers to the row for a physical memory location in an array composed of columns and rows of capacitors used for DRAM modules. This value specifies the number of clock cycles between a Row Address Strobe (RAS) and a CAS, and represents the row address to column address delay for a memory module.
• Trp or tRP, usually expanded as RAS precharge, which represents the number of clock cycles required to end access to the current row of memory, and commence access to the next row of memory, so that tRP = time for row precharge.
• tRAS or Tras, usually expanded as RAS access time measured by the number of clock cycles needed to access a certain row of data in DRAM between the initial data request and the precharge command required to commence the next memory access. By definition, tRAS must be greater than or equal to the CAS plus the tRCD, plus an additional two cycles, to leave time for accesses to complete, as they read or write multiple bits of memory, which DDR (2 bits), DDR2 (4 bits), and DDR3 (8 bits) all do in lesser or greater numbers.

RAM memory timings usually appear as sequences of four numbers separated by dashes, as in 5-5-5-15. This indicates that the CAS, tRCD and tRP values are all equal to five clock cycles, and that the tRAS value is equal to 15 clock cycles. The smaller the numbers that appear in these sequences, the tighter memory timings are said to be. Likewise, larger numbers are said to indicate looser timings. Simply put, lower latency costs more, tighter timings cost more and the combination of the two costs the most where memory is concerned.

Fonte

Eu iria com os tempos mais apertados que eles tendem a ser mais rápidos e a diferença de 166mhz nem será perceptível. Na verdade, ambos são tão próximos que você não notaria qualquer diferença de velocidade. Aquele com a maior classificação Mhz pode ser melhor para overclocking, já que lhe dará um pouco de espaço na cabeça, já que a Intel moderna e todos os chips AMD possuem controladores de memória integrados, assim como o FSB, você também estará com overclocking. Mas, novamente, isso é tudo preferência pessoal, dependendo do que você fará com o seu sistema. Qualquer um ficará bem se você estiver apenas construindo um sistema de estoque que não planeja fazer overclock.