12/8/2022 0 Comments 8088 5mhz memory speed ns![]() In general, because so many basic instructions execute in fewer than four clocks per instruction byte-including almost all the ALU and data-movement instructions on register operands and some of these on memory operands-it is practically impossible to avoid idling the EU in the 8088 at least 1⁄ 4 of the time while executing useful real-world programs, and it is not hard to idle it half the time. A sequence of such fast instructions prevents the queue from being filled as fast as it is drained, and Therefore, for example, a two-byte shift or rotate instruction, which takes the EU only two clock cycles to execute, actually takes eight clock cycles to complete if it is not in the prefetch queue. Both the 80 take four clock cycles to complete a bus cycle whereas for the 8086 this means four clocks to transfer two bytes, on the 8088 it is four clocks per byte. When the queue is empty, instructions take as long to complete as they take to fetch. With the speed of instruction fetch reduced by 50% in the 8088 as compared to the 8086, a sequence of fast instructions can quickly drain the four-byte prefetch queue. Cutting down the bus to eight bits made it a serious bottleneck in the 8088. The speed of the execution unit (EU) and the bus of the 8086 CPU was well balanced with a typical instruction mix, an 8086 could execute instructions out of the prefetch queue a good bit of the time. Meanwhile, the mov reg,reg and ALU reg,reg instructions, taking two and three cycles respectively, yielded an absolute peak performance of between 1⁄ 3 and 1⁄ 2 MIPS per MHz, that is, somewhere in the range 3–5 MIPS at 10 MHz. : 5–98 Performance ĭepending on the clock frequency, the number of memory wait states, as well as on the characteristics of the particular application program, the average performance for the Intel 8088 ranged approximately from 0.33 to 1 million instructions per second. The reason for the reversal is that it makes the 8088 compatible with the 8085. The second change is the pin that signals whether a memory access or input/output access is being made has had it sense reversed. Combined with the IO/ M and DT/ R signals, the bus cycles can be decoded (it generally indicates when a write operation or an interrupt is in progress). : 5–97 Instead it outputs a maximum mode status, SSO. First, pin 34 is no longer BHE (this is the high-order byte select on the 8086-the 8088 does not have a high-order byte on its eight-bit data bus). All of the other pins of the device perform the same function as they do with the 8086 with two exceptions. The main difference is that there are only eight data lines instead of the 8086's 16 lines. The 8088 is architecturally very similar to the 8086. Intel second sourced this microprocessor to Fujitsu Limited. The plastic package version was introduced on July 1981 for USD $14.10 per 100 in quantities. When announced, the list price of the 8088 was US$124.80. The available CMOS version was outsourced to Oki Electronic Industry Co., Ltd. In 1984, Commodore International signed a deal to manufacture the 8088 for use in a licensed Dynalogic Hyperion clone, in a move that was regarded as signaling a major new direction for the company. Successive NEC 8088 compatible processors would run at up to 16 MHz. For instance, the NEC V20 was a pin-compatible and slightly faster (at the same clock frequency) variant of the 8088, designed and manufactured by NEC. ![]() ![]() ![]() There were also several other, more or less similar, variants from other manufacturers. Later followed the 80C88, a fully static CHMOS design, which could operate with clock speeds from 0 to 8 MHz. Variants of the 8088 with more than 5 MHz maximal clock frequency include the 8088–2, which was fabricated using Intel's new enhanced nMOS process called HMOS and specified for a maximal frequency of 8 MHz. These modifications of the basic 8086 design were one of the first jobs assigned to Intel's new design office and laboratory in Haifa. The prefetch queue of the 8088 was shortened to four bytes, from the 8086's six bytes, and the prefetch algorithm was slightly modified to adapt to the narrower bus. The 8088 was targeted at economical systems by allowing the use of an eight-bit data path and eight-bit support and peripheral chips complex circuit boards were still fairly cumbersome and expensive when it was released. The 8088 was designed at Intel's laboratory in Haifa, Israel, as were a large number of Intel's processors. ![]()
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