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Ask HN: Weirdest Computer Architecture?

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Re: Ask HN: Weirdest Computer Architecture?

#91

Post by nrr »

skissane wrote: post #89
nrr wrote: post #87

Earlier quoted context omitted.

About the only thing that's truly limiting about using such an old release of MVS is the 24-bit addressing and maybe the older pre-XA I/O architecture. Having a simulated 3033 running at 10+ MIPS is pretty nice though. (:

> About the only thing that's truly limiting about using such an old release of MVS is the 24-bit addressing I've never used it, but there's a hacked up version that adds 31-bit addressing [0]. It is truly a hack though – porting 24-bit MVS to XA is a monumental task, not primarily due to address mode (you can always ignore new processor modes, just like how a 286-only OS will happily run on a 386 without realising i…

Yeah, I've wondered what the lift would be to backport XA I/O to MVS 3.8j, among other things, but given that it's a pretty pervasive change to the system, I'm not surprised to learn that it's pretty heavy.

To your note about a hypervisor though: I did consider going this route. I already find VM/370 something of a more useful system anyway, and having my own VM/XA of sorts is an entertaining prospect.

Re: Ask HN: Weirdest Computer Architecture?

#92

Post by skissane »

nrr wrote: post #91
skissane wrote: post #89

Earlier quoted context omitted.

> About the only thing that's truly limiting about using such an old release of MVS is the 24-bit addressing I've never used it, but there's a hacked up version that adds 31-bit addressing [0]. It is truly a hack though – porting 24-bit MVS to XA is a monumental task, not primarily due to address mode (you can always ignore new processor modes, just like how a 286-only OS will happily run on a 386 without realising i…

Yeah, I've wondered what the lift would be to backport XA I/O to MVS 3.8j, among other things, but given that it's a pretty pervasive change to the system, I'm not surprised to learn that it's pretty heavy. To your note about a hypervisor though: I did consider going this route. I already find VM/370 something of a more useful system anyway, and having my own VM/XA of sorts is an entertaining prospect.

It arguably doesn't require anything as remotely complex/feature-rich as full VM/XA: it wouldn't need to support multiple virtual machines, or complicated I/O virtualisation.

Primarily just intercept SIO/etc instructions, and replace them with the XA equivalent.

Another idea that comes to mind: you could locate the I/O instructions in MVS 3.8J and patch them over with branches to some new "I/O translation" module. The problem I think with that, is while the majority of IO goes through a few central places in the code (IOS invoked via SVC call made by EXCP), there's I/O instructions splattered everywhere in less central parts of the system (VTAM, TCAM, utilities, etc).

Re: Ask HN: Weirdest Computer Architecture?

#93

Post by nrr »

skissane wrote: post #92
nrr wrote: post #91

Earlier quoted context omitted.

Yeah, I've wondered what the lift would be to backport XA I/O to MVS 3.8j, among other things, but given that it's a pretty pervasive change to the system, I'm not surprised to learn that it's pretty heavy. To your note about a hypervisor though: I did consider going this route. I already find VM/370 something of a more useful system anyway, and having my own VM/XA of sorts is an entertaining prospect.

It arguably doesn't require anything as remotely complex/feature-rich as full VM/XA: it wouldn't need to support multiple virtual machines, or complicated I/O virtualisation. Primarily just intercept SIO/etc instructions, and replace them with the XA equivalent. Another idea that comes to mind: you could locate the I/O instructions in MVS 3.8J and patch them over with branches to some new "I/O translation" module. Th…

I leaned into the "well, what if my own VM/XA" because, uh, VM/CMS has the odd distinction among IBM's operating systems of the era of being both (1) source available and (2) site-assemblable. I've gone through my fair share of CMS and CP generations, which felt like a more complete rebuild of those nuclei than the MVS sysgens I've done.

That there makes me feel a little less confident in an MVS 3.8j patching effort.

Re: Ask HN: Weirdest Computer Architecture?

#96

Post by abs0 »

PaulHoule wrote: post #55
runjake wrote: post #4

Here are some architectures that might interest you. Note these are links that lead to rabbit holes. 1. Transmeta: https://en.wikipedia.org/wiki/Transmeta 2. Cell processor: https://en.wikipedia.org/wiki/Cell_(processor) 3. VAX: https://en.wikipedia.org/wiki/VAX (Was unusual for it's time, but many concepts have since been adopted) 4. IBM zArchitecture: https://en.wikipedia.org/wiki/Z/Architecture (This stuff is comp…

I wouldn't say the VAX was unusual even though it was a pathfinder in that it showed what 32-bit architectures were going to look like. In the big picture the 386, 68040, SPARC and other chips since then have looked a lot like a VAX, particularly in how virtual memory works. There's no fundamental problem with getting a modern Unix to run on a VAX except for all the details. Z is definitely interesting from it's hist…

> "There's no fundamental problem with getting a modern Unix to run on a VAX except for all the details"

Pretty much. The main issue with modern Unx on a VAX is memory size & performance, which combine to make native compiling under recent gcc versions "problematic", so cross building in gcc-10 or 12 is much easier.

The profusion of (from today's perspective) whacky addressing modes have made maintaining gcc for VAX more effort that it would be otherwise, but it's still there and in use for one modern UNx https://wiki.netbsd.org/ports/vax/ :)

You can download https://opensimh.org/ to get a VAX emulator and boot up to play

Simh also emulates a selection of other interesting and unusual architectures https://opensimh.org/simulators/

Re: Ask HN: Weirdest Computer Architecture?

#97

Post by Dr_Jefyll »

dongecko wrote: post #27

Motorola used to have a one bit microprocessor, the MC14500B.

"One Bit Computing at 60 Hz" describes a one-bit design of my own that folks have repeatedly posted to HN. It's notable for NOT using the MC14500... (and for puzzling some of the readers!)

The original 2019 post by Garbage [1] attracted the most comments. But in a reply to one of the subsequent posts [2] I talk a bit about actually coding for the thing. :)

[1] https://news.ycombinator.com/item?id=7616831

[2] https://news.ycombinator.com/item?id=20565779

Re: Ask HN: Weirdest Computer Architecture?

#99

Post by Bluestein »

sliken wrote: post #76
Bluestein wrote: post #15

Earlier quoted context omitted.

> Transmeta Whatever happened to them ... They had a somewhat serious go at being "third wheel" back in the early 2000s, mid 1990s? PS. Actually considered getting a Crusoe machine back in the day ...

They had a great plan, that was promising, and Intel was focused entirely on the pentium-4, which had high clocks for bragging rights, long pipeline (related to the high clocks), and high power usage. However between Transmeta's idea and shipping a product Intel's Israel location came up with the Intel Core series. MUCH more energy efficienct, much better performance per clock, and ideal for lower power platforms lik…

> Sadly transmeta's no longer had a big enough advantage, sales decreased, and I heard many of the engineers ended up at Nvidia, which did use some of their ideas in a nvidia product.

Funny how that came about. Talent finds a way, Now they're all sitting in a 3T ship.-

Re: Ask HN: Weirdest Computer Architecture?

#100

Post by Bluestein »

em-bee wrote: post #74
Bluestein wrote: post #15

Earlier quoted context omitted.

> Transmeta Whatever happened to them ... They had a somewhat serious go at being "third wheel" back in the early 2000s, mid 1990s? PS. Actually considered getting a Crusoe machine back in the day ...

i did get a sony picturebook with a transmeta processor. the problem was that as a consumer i didn't notice anything special about it. for transmeta to make it they would have had to either be cheaper or faster or use less power to be attractive for consumer devices.

I seem to recall them machines not being cheaper, which was my main hope at the time :)
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