The 286's internal registers (2022) | Hacker News Reader

The 286's internal registers (2022)

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73 pointsuserbinator17 comments

I was wondering why the 286 protected mode wasn't more popular. This sums it up pretty nicely https://en.wikipedia.org/wiki/Protected_mode#The_286

This might answer my question here, but it's unclear if the same performance hit happens if the CPU is in Real Mode:

https://news.ycombinator.com/item?id=40700257

I miss the Wang 286 I had, I was dumb and tossed it out when I had to move :(

I go back and forth with it. Once I got some money i bought some old dream machines back. it was great for a while. but At one point i had like 15 retro computers that i almost never used, eventually i went Marie Kondo and gave a bunch away and it feels good to have actual closet space. kept a few that were special. now... about this pile of 30 old hard disks i have... oh and my collection of usb type-b and usb-mini cables...

I did something in between - I kept the physically small systems (Landisk, VAXstation VLC, Mac LC III+, Mac Quadra 610, Cobalt Raq, EdgeRouter, various Pis, et cetera) and some of the more useful larger ones (Amiga 4000, VAXstation 4000/60 and 4000/90, AlphaServer DS25), and I put them to use building NetBSD pkgsrc packages so they're useful.

Considering the fact that I paid less than $100 for the VAXstation 4000/60, for instance, and they go for > $1000 on eBay these days, I'm glad I kept all my VAX hardware. While 286 systems don't cost quite as much, the prices are only going to go up.

Sounds like you live in a computer museum ;) How did you end up owning these?

I kept a handful of older computers, my ZX-81 still sitting somewhere, ZX-Spectrum, Apple Newton. My HP-48GX is used by my daughter. I have a dual CPU 486 machine... I doubt any of these is worth any $'s ...

I think Linux dropped support for 486, right? That was the only thing I remember that supported dual 486.

NCR had a couple of SMP 486 boxen (NCR 3450, 3550 & 3600) that were supported by SCO Unix, SVR4 and (early) NT. I think they had support for OS/2. ALR, Unisys and Compaq made somewhat similar 486s with roughly similar OS support (although I vaguely recall the Unisys stuff was OEMed elseware). The support problem was 486 predated standardized SMP hardware (APIC), so it was all custom hardware.

> I doubt any of these is worth any $'s ...

as always with a legacy $anything the price is for those who really want it.

I have Psion 3 (with a damaged screen cablr, but with a whopping 1MB SSD), it costs nothing, but people selling the working ones for more than $100

I've always had an appreciation for odd hardware, and I've just tried to keep what I like of what I have.

Big fan of the Sinclairs - small, simple, yet filled with all sorts of neat tricks that made them inexpensive and simple. That cleverness makes for a great set of lessons to modern computer programmers and architects.

A dual 486 is a very special beast.. What motherboard is that

tbh not sure. I'd have to dig it out of the crawlspace and have a look. But yeah, seems like those indeed are rare. Had no idea and I guess some chance I'm misremembering and it's a Pentium or something.

My first computer was a 386. There was a reference program I used all the time and I can’t remember it for the life of me. It was menu driven and had a ton of information on hardware, including CPU’s, UARTS, registers and their uses, interrupts etc. Sounds vague I know, but does anyone have any idea what that program was called?

Could it have been Dr. Hardware Sysinfo?

https://www.dr-hardware.com/pghgretro.htm

Were the segment registers (fs, gs) slower than the general registers (ax, dx)? I used to use them all the time as temp variables :/

From the file linked in https://www.vogons.org/viewtopic.php?p=534845#p534845, it looks like 'mov fs, ax' may have been 5 cycles compared to 3 for 'mov dx, ax', with no penalty in the other direction? So probably net faster than using memory instead.

But +15 cycles if you're in protected mode. In this case I think you'd also cause a fault by storing values into a segment register which weren't valid indexes into the LDT/GDT.

Thank you!

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