Newsgroup: it.comp.retrocomputing
Titolo: cpu 80286: Is it really something "retro"?!?

The Intel 80286 (normally abbreviated as 286) processor did not suffer from
the compatibility problems that damned the 80186 and 80188. The 286 chip,
first introduced in 1982, is the CPU behind the original IBM PC AT (Advanced
Technology). Other computer makers manufactured what came to be known as IBM
clones, with many of these manufacturers calling their systems AT-compatible
or AT-class computers.
When IBM developed the AT, it selected the 286 as the basis for the new
system because the chip provided compatibility with the 8088 used in the PC
and the XT. Therefore, software written for those chips should run on the
286. The 286 chip is many times faster than the 8088 used in the XT, and at
the time it offered a major performance boost to PCs used in businesses. The
processing speed, or throughput, of the original AT (which ran at 6MHz) is
five times greater than that of the PC running at 4.77MHz.
286 systems are faster than their predecessors for several reasons. The main
reason is that 286 processors are much more efficient in executing
instructions. An average instruction takes 12 clock cycles on the 8086 or
8088, but takes an average of only 4.5 cycles on the 286 processor.
Additionally, the 286 chip can handle up to 16 bits of data at a time
through an external data bus twice the size of the 8088.
The 286 chip has two modes of operation: real mode and protected mode. The
two modes are distinct enough to make the 286 resemble two chips in one. In
real mode, a 286 acts essentially the same as an 8086 chip and is fully
object-code compatible with the 8086 and 8088. (A processor with object-code
compatibility can run programs written for another processor without
modification and execute every system instruction in the same manner.)
In the protected mode of operation, the 286 was truly something new. In this
mode, a program designed to take advantage of the chip's capabilities
believes that it has access to 1GB of memory (including virtual memory). The
286 chip, however, can address only 16MB of hardware memory. A significant
failing of the 286 chip is that it cannot switch from protected mode to real
mode without a hardware reset (a warm reboot) of the system. (It can,
however, switch from real mode to protected mode without a reset.) A major
improvement of the 386 over the 286 is that software can switch the 386 from
real mode to protected mode, and vice versa. See the section "Processor
Modes," earlier in this chapter for more information.
Only a small amount of software that took advantage of the 286 chip was sold
until Windows 3.0 offered standard mode for 286 compatibility; by that time,
the hottest-selling chip was the 386. Still, the 286 was Intel's first
attempt to produce a CPU chip that supported multitasking, in which multiple
programs run at the same time.
(thanks to: © 2006 Pearson Education, Que Publishing. All rights
reserved.800 East 96th Street Indianapolis, Indiana 46240)

we non e' che ci devi convincere eh..sappiamo ben che quella roba non vale
un cazzo,x di + sapendo che e' olivetti..sput
-- 
erik christille
presidente e fondatore del V.R.G
valle d'aosta retrocomputing group

 ha scritto nel messaggio 
news:200611101...@mynewsgate.net...
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muori
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 ha scritto nel messaggio 
news:200611101...@mynewsgate.net...


 plurale maiestatis
mitico! abbiamo finalmente un troll colto...
peccato solo che la linea mi faccia difetto in questi giorni grigi
d'autunno, altrimenti potrei per tempo replicare alle Vostre inserzioni,
Signore.
-- 
"...non potresti desiderare di essere nato in un'epoca migliore 
di questa, in cui si e' perduto tutto..."         S.WEIL

 The Intel 80286 (normally abbreviated as 286) processor did not suffer from
[...]
PER FAVORE BASTA!
Grazie.
	Fabio.

 mitico! abbiamo finalmente un troll colto...
Grazie a DIO sei qui' !!!!
Bradipo, puoi pensarci tu per favore.... :)
Grazie mille... :)
Ciao.
	Fabio.

 Bradipo, puoi pensarci tu per favore.... :)
se n'e' gia' andato, ca%%o! non faccio in tempo ad accorgermene che si
sono gia' dileguati. non e' giusto. mi sento come obelix...
fate qualcosa, vi prego...
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