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Unformatted text preview: k. On the other hand, fast storage is always more expensive than slower storage. SRAM costs more per byte than DRAM. DRAM costs much more than disk. The price and performance properties of different storage technologies are changing at dramatically different rates. Figure 6.15 summarizes the price and performance properties of storage technologies since 1980, when the ﬁrst PCs were introduced. The numbers were culled from back issues of trade magazines. Although they were collected in an informal survey, the numbers reveal some interesting trends. Since 1980, both the cost and performance of SRAM technology have improved at roughly the same rate. Access times have decreased by a factor of about 100 and cost per megabyte by a factor of 200 (Figure 6.15(a)). However, the trends for DRAM and disk are much more dramatic and divergent. 294 CHAPTER 6. THE MEMORY HIERARCHY
While the cost per megabyte of DRAM has decreased by a factor of 8000 (almost four orders of magnitude!), DRAM access times have decreased by only a factor of 6 or so (Figure 6.15(b)). Disk technology has followed the same trend as DRAM and in even more dramatic fashion. W...
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- Spring '10
- The American