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Questions tagged [80286]

The Intel 80286 16-bit microprocessor. Use only for questions specifically about the processor; DO NO USE to mean ‘286-class machine’.

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Did any software attempt to perform 8086 emulation on the 80286 using LOADALL, in the vein of the later virtual 8086 mode of the 80386?

I know that Virtual 8086 mode was added on the 80386 to make it possible to run old applications in a Protected Mode environment. The 80286 had a lot of shortcomings, such as not being able to switch ...
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2 votes
2 answers
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Commodore 1352 mouse converter

My Commodore PC30-III can only handle a Commodore 1352 mouse, but it is practically impossible to buy one. I own a couple of Amiga and serial PC mice that if I plug in, the buttons seem to work, but ...
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0 votes
1 answer
318 views

What's the heritage of 80286? [closed]

80186 introduced some instructions for HLL features. 80286 introduced some instructions for protected mode, and provided some multitasking ability with external MMU which was never intended for PCs ...
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10 votes
1 answer
475 views

Did the Harris 80C286 differ from Intel's 80286 in its behaviour?

The Harris company, well known for being an early second source making x86 chips under license, eventually produced a fully static CMOS 80C286 of their own design (later known as the Intersil 80C286 ...
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4 votes
1 answer
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Instructions added with the Intel 80286 [closed]

The 80286 processor added these instructions: ARPL, VERR, VERW, LAR, LSL, SMSW, SGDT, SIDT, SLDT, STR, LMSW, LGDT, LIDT, LLDT, LTR, CLTS. To help understand how this was implemented I am looking for ...
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11 votes
2 answers
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What was this OS / Application on a 80286?

I was hoping, that someone could help me find the name of the operating system that was originally (I guess) used on the 80286 (the later ones with 12MHz). Before I eventually installed DOS-5.0 and ...
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10 votes
1 answer
639 views

How does the 80287 process infinity values?

Modern x86 processors have an infinity control bit on the x87 FPU control register. This is bit 12 and it enables processing of infinity values in a manner that is compatible with the 80287 ...
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18 votes
4 answers
3k views

80286 real mode emulator for 8086

While trying to use a "modern" sound card (an Aztech Sound Galaxy Pro 16 II) in an XT compatible 8086 computer, I encountered the problem that the drivers and tools (like the mixer initialization tool ...
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13 votes
3 answers
890 views

0F1h opcode-prefix on i80286

On Intel iAPX 80286, as I recall from experience, the undocumented – officially unassigned – opcode position 0F1h was actually decoded as an instruction prefix, thus counting for maximum allowed ...
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18 votes
3 answers
3k views

How to switch an 80286 from protected to real mode?

It's pretty well documented how to get the 286 from real mode to its 16-bit protected mode. It's also widely stated that the 286 had no officially supported way of going back from protected mode into ...
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6 votes
5 answers
664 views

Did the PC/AT-bus use its expanded address space?

The system bus of the IBM PC had 8 data lines and 20 address lines, in a logical correspondence to the 8088 CPU. The AT added a second inline edge connector to expand this to 16 data lines and 24 ...
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4 votes
1 answer
488 views

Did the 286 go out of its way to follow the 8088 bus protocol?

In general, different CPUs don't use the same bus protocol. A 16-bit CPU would not in general be expected to use the same protocol as an 8-bit CPU. For example, the 68000 would not be expected to use ...
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10 votes
1 answer
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Which operating systems for 80286 computers allowed a process to use more than 128k data?

Out of all the operating systems for the 80286 processor I found, only two make use of the protected mode's ability to load more than one segment for text and one for data. These are MS-DOS (through ...
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5 votes
2 answers
682 views

What 286 chipsets support UMBs?

I read in some forums that some 286 boards support UMBs and thus can load drivers and TSRs into the upper 384 KiB of conventional memory. What chipsets support this and do I need special drivers?
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7 votes
1 answer
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How do you put a 286 in Protected Mode?

From the Art of Intel x86 Assembly, Page 149, The 80386 added four control registers: CR0-CR3. These registers extend the msw registers of the 80286 [...] The book says earlier that, The 80286 ...
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11 votes
5 answers
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80286 pricing and availability

Most information online states that the 80286 (or iAPX 286 as it was initially known) was first available in February 1982. But information about it from this time is hard to come by, and famously it ...
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5 votes
1 answer
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How to diagnose a failed capacitor on the mainboard?

My Fox II 286 mainboard just blew a capacitor. I haven't yet powered it on, so maybe the cap was bad. How can I diagnose this problem, and eliminate other bad caps?
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7 votes
2 answers
529 views

What DOS software can I test a QIC-02 tape drive with?

I got a Wangtek 5150EQ tape drive that connects to a dumb (made of a bunch of 74-series logic chips) 8-bit ISA tape controller card. The controller card has a bunch of DIP switches which I used to ...
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6 votes
1 answer
881 views

First 80286 Based Computer

The 80286 was released in early 1982. The IBM PC AT, which used it, was released in late 1984. Two and a half years is a long time to design a new computer that is a fairly modest upgrade on existing ...
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5 votes
2 answers
762 views

Jumper and switch settings for 286 Suntac mainboard

I have a 286 mainboard here, which is I think very similar to this one here at stason.org. Below is an overview image, and a link to a album with details. However there are still some discrepancies, ...
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5 votes
1 answer
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What kind of SIMMs can 286 PCs use?

I have a 286 Board (Octek Fox II 286) which takes up to four 30 pin SIMM modules. The manual however (http://www.minuszerodegrees.net/manuals/Octek%20-%20FOX-II%20286%20(12_16%20MHz%20versions).pdf) ...
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5 votes
1 answer
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Manual or jumper settings for mainboard PWA-286C

I have an old mainboard, type PWA-286C, running a 10 MHz Intel 80286. I have no manuals, so I am looking for documentation on it. I am especially wondering if there is a connector for the real time ...
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5 votes
1 answer
718 views

What was the fastest third party FPU?

For both the x86 and SPARC based machines, it was possible to get not only FPUs installed as a separate, discrete IC, but also third party FPUs. In particular, I've read about Weitek on Wikipedia. ...
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15 votes
3 answers
3k views

Replacing 80286 with 68000

Suppose you wanted to take a 286 PC and replace the CPU with a 68000, not at the initial design stage, but actually modifying the finished machine, on the theory that they both have 24 bits of address ...
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8 votes
1 answer
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Is a Heatsink Needed for an Intel 80286?

I noticed my IBM XT 286 has no heatsink on the CPU nor a fan of any kind (only the PSU has a fan). I realize this was fine when it was built, but for longevity purposes, should I put a heatsink on it? ...
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23 votes
4 answers
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What conventions and language extensions did people use to program the 8086 and 80286?

The 8086 is a 16 bit processor with a 20 bit segmented address space, famous for being used in the IBM PC. It is also infamous for being tricky to program for. I am currently writing what is ...
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24 votes
4 answers
4k views

How did the Apple II forward binary instructions to the Z80 software card with CPM?

Microsoft produced the Z80 Softcard for the Apple II enabling it to run CPM and many Z80 binary programs. This seems to be an unthinkable achievement. (For a kid who had an Apple IIe but was only a ...
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58 votes
3 answers
6k views

How does the LOADALL instruction on the 80286 work?

This undocumented instruction existed in the 80286 and, I believe, the 80386. I think it was added while debugging the chip, so the engineers could quickly put the processor into any state and test it ...
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23 votes
4 answers
2k views

How can I access an old pre-IDE disk?

I have a wonderful Zenith SupersPORT 286 laptop (ZWE-0200-40) whose power circuitry seems faulty and it no longer powers up. I have useful material on the disk which I'd like to extract. The disk (a ...
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36 votes
3 answers
5k views

80286 can switch from real mode to protected mode - but why not back?

It's been a while, but I've read in a system programming book that you could switch your Intel 80286 CPU from the normal real mode to a more powerful protected mode. I clearly remember that they said ...
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