Talk:Intel 80286

Protected And Real

The article is somewhat confusing because it talks about Concurrent DOS running multiple real mode programs in protected mode, but elsewhere says the CPU doesn't allow it. E step 286 allows multiple real mode programs to run using LOADALL. Concurrent DOS was smart enough to do this Microsoft was not. There is no *technical* reason Microsoft couldn't have supported multiple real mode DOS programs at once in Windows 286 as the article implies.

It's also confused because it talks about the keyboard controller hack but DOS rarely used this because it used LOADALL on later 286 processors in order to implement the extended memory RAM disk so didn't have to leave real mode as the article implies.

Yes LOADALL is firmly in the 'dark arts' of x86 programming but it existed and was used successfully.

82.70.14.226 (talk) 17:50, 1 April 2018 (UTC)

Unknown subject

and could run up to 12.5MHz.

I removed this, because I think that it is wrong, but I'm not sure. I believe that a 16MHz 80286 was pretty common, and my father said that his first computer had a 20MHz 286 CPU. Can anyone confirm or deny? -- Stephen Gilbert

UPDATE: I am sure. Check this page: http://www.pcguide.com/ref/cpu/fam/g2I80286-c.html -- Stephen Gilbert

It seems there were 25MHz 286s too, though not from Intel. Crusadeonilliteracy

codenamed iAPX

I removed this because the 80286 was not codenamed iAPX. The iAPX was a completely different processor family developed by Intel in 1981. At first the family consisted of a two-chip general data processor, and a single-chip interface processor. Eventually Intel added a bus interface unit and a memory control unit. Please see a great iAPX website at http://www.brouhaha.com/~eric/retrocomputing/intel/iapx432/

Chris Thames mavroxur@hotmail.com

Exiting protected mode

However, the 286 couldn't revert to real mode, so protected mode wasn't widely used until the appearance of the 386, which could go back and forth between modes.

It should be noted that although this is technically true, IBM and others created workarounds for this limitation early on, so it's not as big a problem as the article makes it sound.

References: Protected mode overview Triple-fault technique

Tim Peterson 18:03, 22 Apr 2005 (UTC)

I've edited the description of real mode reentry, hopefully making clear that it had to depend on external circuitry (to cause a processor reset) plus specialised BIOS code (to help restore OS status). I removed details of /how/ the reset would be triggered (earlier method thru a KB controller output wire, later by converting a shutdown status to reset) as well as the story about "clever programmers", where in fact all this was devised by Intel and circulated under NDA.

Ninho (talk) 20:49, 4 November 2009 (UTC) Ninho

The 80286's performance is more than twice that of its predecessors (the Intel 8086 and Intel 80186)

You know that section is pretty confused: The 80286 was perhaps twice as fast as it's predecessor, the 80186, because it typically ran at a higher clock speed. But it was much faster than the computer most people had, because like in the 80186, calculation of the more complex addressing modes (such as [BX+SI]) were performed by dedicated hardware; the widely used 8088 had microcoded intstructions (like a RISC processor) that took many clock cycles to complete. In fact, the performance increase per clock cycle between the 80186 and the 8086/8088 may be the largest among the generations of x86 processors. In comparison, (and speaking as one who used these processors) the step between the 80186 and the 80286 was negligable. On the other hand, I hate to say that you are just wrong: most people went straight from an 8MHz 8088 to a 16MHz 80286, and they were looking at a massive difference.

I looked at the 8086 and 80386 instruction manuals, and it seems to me that there is a difference, but i dont see the doubling in many common instructions. It might be true that all the complicated memory addressing is much slower, but for example add went from 3/10 to 2/7. It's true that push/pop are much faster etc, but i guess there is not much more than a doubling of performance per cycle overall. The jump from 386 to 486 saw an approximate doubling in performance, too. so i dont understand this statement. anton

After review the manuals, I noticed that I was using an 80186 manual. The 80186 is probably closer to the 80286 in terms of performance than the 8086. anton

Possible err in para 1

0.21 million instructions per clock? (first paragraph). Surely not? prehaps 0.21 MIPS, but not 0.21 M IPC?!. (Sam Cadby) —Preceding unsigned comment added by 217.33.137.68 (talk) 16:47, 26 September 2007 (UTC)

Another thing that seems to make no sense is the fact that the 6 MHz version clocks in at 0.9 MIPS, while it says that the 12 MHz one comes in at 2.66. That is almost 3 times the performance of the 6 MHz version while only twice its clock speed. The only thing I can think of is that the 6 MHz version could be bottlenecked by memory speed (the 12 MHz version accesses it faster because the memory also runs at 12 MHz?). But that's only me making a guess, as I don't remember how the memory bus was designed on these old machines. 84.49.75.226 (talk) 11:02, 25 May 2016 (UTC)

4 MHz 286 chip?

I was wondering if someone should write something about the Intel C80286-4 in the article. The processor's maximum clock speed should be 4 MHz, and was for a short period manufactured and used in some personal computers, for example, the Ericsson 286 (which I personally owned once). The processor has LCC packaging. There seems to be conflicting information about this processor on the internet, and rarely have any information on the LCC packaged processor. Not sure about the speed though, maybe someone knows a bit better?
See more information at [1]. --62.142.251.79 (talk) 01:50, 21 February 2008 (UTC)

Post facto correction: I didn't own an account back in 2008. Now that I do, here's my signature for the above comment. Molivil (talk) 20:18, 1 November 2019 (UTC)

80286 in PLCC only?

I have a 80286 in a CPGA format. Ginbot86 (talk) 22:42, 16 August 2008 (UTC)

80286s were produced in several formats and packaging during the product's lifetime, also depending on the class of applications. DIP (dual in line) was what it looked like in IBM PC-ATs and clones back in the times, the fact that all illustrations of the article show later square packages is misleading and regrettable IMHO. Can someone upload a photo of a typical genuine i80286-10 DIP typical of a 286-based AT ? I have 2 pieces here, unfortunately I don't do photos :( Ninho (talk) 15:34, 5 November 2009 (UTC)Ninho

Performance jump vs 8086

This comparison is quite lengthy but conveniently ignores the 80186 which was somewhere inbetween the two series in terms of performance. It was not popular as a PC processor but this is an article about the chip, not specifically PC history, so surely it deserves mentioning here. CrispMuncher (talk) 20:45, 15 November 2009 (UTC)

Removed misleading paragraph about protected mode

I have taken the liberty, under the "be bold" rule, of simply deleting the slightly breathless and extremely incorrect claim that the 286 gave "the first glimpse of memory protection mechanisms that were previously exclusive to mainframes" mwa mwa mwa. Most 16-bit microprocessors offered this feature in some form - for example, the Motorola 68000 had protected mode at its introduction in 1979 and full virtual memory support with the 68010 shortly thereafter. In fact, the x86 family was unusual in not offering it from the get-go. 87.194.209.163 (talk) 17:08, 28 November 2010 (UTC)

File:The register set of 80286.jpg Nominated for speedy Deletion

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This page has been deleted as it constituted a copyright violation. --Matthiaspaul (talk) 14:34, 30 October 2011 (UTC)

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Current-era uses and legacy?

Articles about other major chips feature current- or recent-era uses (where they have persisted in niche fields), and a section on what remains the legacy of the chip. I rather fancy something similar in here. I'd imagine by the time when Windows 3.1 came around, computers with this chip fell out of favour and then general usage, as many computer users until then were fine with DOS, Lotus 1-2-3, WordPerfect, and other by-and-large text mode applications.

Chances are that perhaps these paragraphs must have somehow already existed and then culled along with and after recent(ish) low-quality edits, which in turn were part of a school project in India. -Mardus (talk) 17:43, 4 August 2012 (UTC)

Is this correct? The math doesn't add up.

The 6 MHz, 10 MHz and 12 MHz models were reportedly measured to operate at 0.9 MIPS, 1.5 MIPS and 2.66 MIPS respectively.  — Preceding unsigned comment added by Erickdingess (talk • contribs) 19:42, 4 May 2015 (UTC) 

It could be that instruction fetch from the memory chip would be a contributing factor. Dannyniu (talk) 01:54, 11 September 2016 (UTC)

Could some1 add a layout?

There is a good photo of 286 die. But what region dedicades to what? What function handles each region on a photo? Could be nice schnematics, and my post is rather feature request; For those who is familiar with drawing colored rectangles in paint and adding textual caption briefly describing what exactly each region of chip is dedicaded for.. t.y. in advance ;) — Preceding unsigned comment added by 91.246.99.112 (talk) 20:15, 8 July 2017 (UTC)

OS Support for Protected Mode

    "The protected mode of the 80286 was not utilized until many years after its release...
     For example, in 1986 the only program that made use of it was VDISK..."

The above statement under "OS Support" is inaccurate.
It is even contradicted by the last paragraph of the same section, mentioning Xenix in 1984.
I know that AT&T showed protected-mode Unix running on the 6300 PLUS at Comdex in October 1985.

Proposed merge with Intel 82284

No apparent reason why the clock driver should not be part of the article for the chip. Ifnord (talk) 01:34, 27 June 2018 (UTC)

Support per nomination. Polyamorph (talk) 07:42, 27 June 2018 (UTC)

I don't find it that obvious when 8284 and other supporting chips for 8086 have separate cross-linked articles too. But I suspect 82284 is not sufficiently notable on its own and it's unlikely to grow out of stub, so I'm not opposing.—mwgamera (talk) 00:36, 30 June 2018 (UTC)

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