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Comment by mysterydip | Hacker News Reader

What I find interesting is things like the Atari Portfolio and HP 200LX could run their versions of DOS for quite a while on a couple AA batteries.

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While Atari Portfolio used the CMOS version of 8088, I believe HP ones made the jump to 80186 (or compatibles) which AFAIK had, among other things, dynamic frequency setting

Correct - the x00LX (I think the 95 also) were one of the few mass produced computers to use the rare 186.

The HP 200LX and similar used a 186-compatible CPU called "Hornet". Using an actual 80186 in a PC compatible would have been damn near impossible; the 186 was a system-on-chip design that had built-in timers, an interrupt controller, and other gubbins. Some of these were mapped to devices that had other devices mapped to them in the PC design, so building a 186-based system that met the common threshold for PC compatibility (i.e. it ran the IBM versions of Lotus and Flight Simulator acceptably well) was a nearly insurmountable task.

Because it acted more like a real OS, with user programs calling through driver APIs rather than touching the hardware directly, with the right driver support Windows could run on a 186-based system; one (the Tandy 2000) was used to develop Windows 1.0's color modes because it had a high-resolution 8-color display before the EGA came out: https://www.1000bit.it/lista/t/tandy/tandy2000_ad.jpg

ISA-compatible "clones" of the 186, like the NEC V40 and the "Hornet", did not have the SoC problem and could be used in PC-compatible system designs.

It was never really clear to me if the "Hornet" was a custom design Intel did for HP or if "Hornet" was just the codename for the 80C186EA, a 186 with added powersaving support. Either way those palmtops were quite cool machines.

For what it's worth, I've used a HP 200LX to confirm that some undocumented details (found by disassembling microcode) work as expected:

    REP BOUND             only compares against lower bound
    REP MUL               result in AH (byte) or SP (word)
    REP IMUL              result in CH (byte) or BP (word)
    REP IMUL reg,r/m,i16  first operand ignored, 32 bit result in DX:AX
    REP IMUL reg,r/m,i8   first op ign., AH=result bit 23..16, AL=bit 7..0
    AAM 00H               no "divide by zero" exception, AH=FFh, AL unchanged

So it's certainly based on the 80186 microcode, as none of these instructions do the same on any other x86 chip.

This is perhaps the comment that most aligns with a username I’ve ever seen ;)

In other words, it has a 186-class ISA but isn't the actual 186 SoC.

Thanks for the best explanation of the '186 I've seen in 30 years. :-)

No problem! The more you know, right?

I mained a used Tandy 2000 for a while as a kid/teenager. Back when it came out, computers still came with full technical docs, including Intel's extensive 186 documentation. I've forgotten things about that beleaguered chip many enthusiasts never knew.

Research Machines made a sizable inroad into UK schools with their range of computers from the late 1970s to early 1990s.

One such example is the RM Nimbus: https://www.computinghistory.org.uk/det/41537/RM-Nimbus-PC-(...

It had a 186 from the very first models, and was later re-branded as PC-186 when they introduced their 286 model.

Indeed so. The BBC Micro Master 512 was the only other one I saw.

IIRC they had some basic "suspend to RAM" where when they closed they just barely kept the RAM alive and didn't power anything else.

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