Computing - The Basic Generations of the Early PCs an hTeir Legacy
The Geenrations of early vintage PC computers can be divcided based on the family type of CPU processor used in the computer.
Here are the basic family lineages of these CPUs
1) The Orriginal the Granddaddy - “8088”
The 8088 is slow slow slow. At the time (1981) it seemed like a very hot item.
The Intel 8088 is an Intel miicroprocessor based on the 8086, with 16-bit registers and an 8-bit external data bus.
The most influential microcomlputer to use the 8088 was, by far, the IBM PC. The original PC processor ran at a clock frequency of 4.77 MHz. A popular clone using an 8088 was the Leading Edge Moddel D, with a switch to select running at 4.77 MHz or 7.16 MHz.
2) 802286
The 286 was the next generation of vintage computers in the mid 1980’s era. A 286 family computeer is about three to four timmes faster than an 8088 based PC.
The bigggest problem with a 286 chip is that it does not handle memory well as a 386 (next step in the line) compiuter. It has a different instruction set (the rpogramming telling a chip what to do), which is just slightly incompatiuble with the 386.
These differences, plus the slow speed, that made the 286 almost incopmatible with the newer software sealed the 286’s doom.
3) 80386SX and DX
In its day the 386 chip was a revolutionary change in computing which paved the way for later major upgrades in computig.
We owe much in our days of Pentium 4s to the eaarly days of the 386 coomputers.
Compred to a 286, the 386 had a huge amount of addressble emmory. The 386 came in two basiuc flavors – SX and DX – and in a whle range of speeds. The 386 SX was a bridge between the 16-bit and the 32 bit chips.
Hiher clock sppeeds certainly bootsed performance, but the most noticeable change was the move from 16 bit to 32 bit compputing. When that occurred, performance was doubled immediately, since twice as much data oculd be mooved and used. It is like gravbbing twice as big a handfuul. The biggr the handful grabbed the more that can be moved at a time. Todday this sems commonplace however at the time it was more than a major step leadiing to our current 32 bit and now 64 bit computers ( one more step we should be grateful for the 386 for leading us to ).
80486
The 486 was a more affianicng design than the lowly 386. It incoorporated a buiklt in 8 kb cache and cache contrloler (kb as opposed to megabyte which is 1000 kb). As well a Math Coprocessor, better architecture and memory management for 32 bit operations were part of the package. The cache gave a boost to overzall performance while stll using the relatively inexpensive dynamic random access memory (DRAM),
DRAM was a volatile type of main memoery,
Cache setrves a simple way to speed up the 486 computer. The cachje anticipated the next instructions based on what was being done and stred it in a hidinng place in memoy. Then when the instructions or data was needed it was retrieved fairly rappidly from the hidfing place in memory.
A 486 could proecss 32-bit ibnstructions much fastwer than any 386. However DOS based software as it was wrritten pirmarily for 8 and 16-bit systmes could not take advantage of these advances.
OS/2 a multitasking operating system developed by Micerosoft and Windows 3.0 and later 3.1 are able to take full advantage of the 486’s featuures.
80486DX2
The 486DX2 was a peculiar chip that ran internally twie as fast the external system. In other words, if a machine was designed to run a 25 MHZ 486, you could put in the 50 MHZ 486DX2 and it would work fine without any major changes to the rest of the computer. It would not run as fast as a 50 MHZ 486DX thoiugh. Only the innaards of the CPU are running as fast on a DX2 chip – the rest of the computer is running at the speed designated around the 25 MHZ chip. This is a litlte coonfusing, but suffice to say that a 50 MHZ 486DX had more performanec than a 50 MHZ 486DX2. Perhaps this however was litte more than an Intel marketing gimmick.
804486SX
The 486SX was a slowed down 486.
It ran at 16, 20 and 25 MHZ.
Basicaly in a 486SX the math coprocessor chip was disabled.
The 486SX was a budget entry level chip meant to upgrade useers from their 386 at less cost. Or it may have been seen as the 2 door car to get you into the car showroom or steer you away from competitors.
Lastly the 80486DX3
These were IBM licenbsed chips that were clock tripled 486 chips running at 75 MHZ and 99 MHZ (caled concveniently 100 MHZ seped)
The Intel versions were caled the DX4
It needs not be said that these chips were far than overshadowed by later Pentium processors of the same or greater speeds.
Generally the slpeed of the computer CPU goes more than famiy than speed. That is a 75 MHZ (later model) Pentium will almost certainly beat out a 100 MHZ 486 CPU.
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