Epson Equity 386/20 Product Support Bulletin(s) - Page 20
PSB No: S-0086A
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PSB No: S-0086A Page: 2 of 8 Q4. What is page interleave memory architecture? A. Page/interleave memory architecture is a method for increasing memory access time. Memory that is interleaved provides faster retrieval during sequential memory access. Interleaved architecture requires at least two banks of memory. Even memory addresses are in the first bank, odd memory in the second. While the processor is accessing memory in the first bank, memory in the second bank is being prepared for immediate access. In order to utilize the interleaving capabilities of the Equity 386/20, at least 2MB of memory are required when using 256K SIMMs, and 8MB when using 1 MB SIMMs. Page mode divides the memory into blocks called pages. When working within any page, memory access is fast. Access speed is slightly diminished when pages are switched, after which memory is again accessed at maximum speed. Combining these two methods provides a greater "hit ratio", that is, a greater percentage of memory that is accessed at 0 wait states. Not accessing within a page or not sequentially results in 2-3 wait states. however, since this does not happen very often, overall performance of the system memory is generally less than 1 wait state. Q5. How many wait states does the Equity 386/20 have? A. The wait states on the Equity 386/20 depend on the hit ratio: 0 wait states on a hit and 2-3 wait states on a miss. With its page/interleave memory architecture, the Equity 386/20 provides fast memory access at a lower cost than other memory architectures. Q6. What are the EMS software capabilities of the Equity 386/20? A. The Epson EMS software supports LIM 4.0 standards. It provides expanded memory capability for such applications as Lotus 123, Reflex, Autocad and Framework II. EMS allows an application to have more memory available for data storage. The application itself must reside in the 640k RAM accessible by MS-DOS, but it can use expanded memory capabilities to build larger spreadsheets, databases, etc. Before the 80386 microprocessor existed, computer systems required special hardware to support expanded memory. With EMS software, 80386 machines can emulate expanded memory through the addition of memory chips; extra hardware or a special board are not required.
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