CPU 8088 vs. Pentium

1. CPU 8088 vs. Pentium TEEL 4011 Prof. Jaime José Laracuente-Díaz

2. CPU 8088 • Anteriormente hablamos sobre la configuración básica del CPU basado en el INTEL 8088. • Recuerde que podemos construir direcciones de memoria de hasta 20 bits en esta arquitectura de microprocesador. • Recuerde que el data bus posee 8 bits.

3. CPU 8088 • Es importante recordar que las líneas de address y data AD0-AD7 tienen la capacidad de funcionar en el modo duplexing. • Es decir, podemos enviar address o data a través de las líneas aunque no de manera simultánea.

4. CPU 8088

5. Adelantos en el Pentium • Pipelining • Algunas instrucciones se pueden realizar en el Pentium con tan solo un ciclo del reloj, lo que antes tomaba hasta 16 ciclos o más. • Se añade el cache memory. Este puede ser interno o externo al micro. • El interno está diseñado para ser muy rápido.

6. Cache Memory • Definición de Wikipedia • A CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations. As long as most memory accesses are to cached memory locations, the average latency of memory accesses will be closer to the cache latency than to the latency of main memory.

7. Cache Memory Diagram of a CPU memory cache

8. Cache Memory • When the processor wishes to read from or write to a location in main memory, it first checks whether a copy of that data is in the cache. If so, the processor immediately reads from or writes to the cache, which is much faster than reading from or writing to main memory.

9. Cache Memory • The diagram shows two memories. Each location in each memory has a datum (a cache line), which in different designs ranges in size from 8 to 512 bytes. The size of the cache line is usually larger than the size of the usual access requested by a CPU instruction, which ranges from 1 to 16 bytes.

10. Cache Memory • Each location in each memory also has an index, which is a unique number used to refer to that location. The index for a location in main memory is called an address. Each location in the cache has a tag which contains the index of the datum in main memory which has been cached. In a CPU's data cache these entries are called cache lines or cache blocks.

11. Cache Memory • Most modern desktop and server CPUs have at least three independent caches: an instruction cache to speed up executable instruction fetch, a data cache to speed up data fetch and store, and a translation lookaside buffer used to speed up virtual-to-physical address translation for both executable instructions and data.

12. Cache Memory • However, of all microprocessor units sold (including embedded processors), most of them do not have any cache[1] -- mostly to reduce cost, but sometimes to improve the determinism of a real-time computing system.

13. Adelantos en el Pentium • Además, se añadió un “math coprocesor” de manera interna en el micro. • Este realiza las funciones de matemática de manera más rápida que los coprocesadores. • Además, existen los “internal dual integer processors and branch prediction” .