3.3. Half-size Row Buffer: Challenge or Opportunity
Even though Half-DRAM can effectively reduce the activation
power, it may induce more activations because of the smaller
row buffer size. To justify the feasibility of Half-DRAM, we
evaluate the performance impact of half-size row buffer. We
first define the ratio of crossing half row (CHR ratio) as the
percentage of two requests referencing to the same row but
different half rows when Relaxed-ClosePage policy is applied.
The lower the ratio is, the more requests are served within
a half row. Specifically, zero CHR ratio means all requests
go to the same half row at each memory access and there is
no performance penalty at all. Note that we only count the
requests that have row buffer hits, other requests that close the
row immediately (due to row conflicts) have been excluded.
Two CHR ratios are defined in Equation 3 and 4. The absolute
CHR ratio represents the percentage of half row crossing
over all requests, while relative CHR ratio shows the actual