Re: Is Parallel Programming Hard, And, If So, What Can You Do About It?

On 5/22/2025 7:12 AM, Torbjorn Lindgren wrote:

BGB  <cr88192@gmail.com> wrote:

I also remember from some early 90s PCs some CD-ROM drives that used
some sort of non-standard interface. Typically, they would plug into an
ISA card with a cable that was (IIRC) somewhat narrower than a normal
IDE cable (I remember it being around the width of a floppy cable; two
ends with a direct connection, and no twists, unlike a typical floppy
cable which usually has part of the cable twisted).
>
Not entirely sure what it was. Wasn't an IDE/ATAPI CD-ROM though, do
know this much at least...
>
Digging more, there was apparently a proprietary 34-pin Sony connector,
which does at least resemble what I remember (and some of the drives do
look like the drives I remember seeing).

 The common pre-ATAPI CD-ROM interfaces were SCSI, Panasonic/MKE,
Mitsumi and Sony, early on there was also LSMI/Philips but they
switched to one of the other fairly early. Which of these were most
common isn't easy to tell any longer.
 There were cheap dedicated interface cards for all of these but most
people bought them bundled with soundcards which included the correct
interface on it. These cards (both dedicated and on soundcard) were
often PIO-only (instead of DMA) which was fine for a 1/2/4x CD-ROM but
not much else.
 Later soundcards often had all three "main" interfaces to reduce the
number of SKUs they need and make it easier for customers, later
soundcards switched to providing a (usually gimped) ATA interface -
which then was removed a few years later as ATA interface was
everywhere already.
 Panasonic & Mitsumi uses unkeyed 40-pin cables (unkeyed IDE cables can
be used) while Sony went with the 34-pin floppy cable. In all cases
they were not compatible with actual IDE/ATAPA or floppy cards despite
the cable fitting... Yes, there were multiple incompatible non-IDE/ATA
CD-ROM with 40-pin connectors because OF COURSE...
 

I was remembering the 34-pin cables here. But, yeah, I do remember them plugged into soundcards, however, trying to look up anything here just flooded the results with people talking about the 4-pin audio cable.
I remember them being not exactly the same as floppy cables though:
Floppy cables usually had 1 or 2 connections, with the last (or only) connection having a small section of the ribbon cable cut out and twisted over (where twist="A:", no twist="B:"). There was no twist in the CD-ROM cables that I remember.

The soundcard ATAPI headers that replaced them were often usable with
disks with the right drivers but performance was usually not very
good.
 

OK.
By the time of ATAPI CD-ROM drives, these were typically plugged into the MOBO.

 

*: Had once encountered a computer (that at the time was being
discarded, but I got it and had it for a while). It had SCSI drives, and
also the weirdness that rather than the CPU and RAM being on the
motherboard, it was on a riser card (the MOBO was IIRC effectively just
card slots, IIRC they resembled 16-bit ISA slots buts with a long
extended part on the front; similar to the "VESA Local Bus" IIRC).
>
IIRC, no connectors on the MOBO (apart from power IIRC), all of the
external connections (like VGA and mouse/keyboard) being on riser cards.
>
I remember the CPU riser card apparently having dual 486DX's, but from
what information I can gather, multi-socket systems weren't a thing with
the 486, so don't know what was going on there. Beyond this, was SIMM
RAM, and a lot of other stuff you would normally see on the MOBO
(excluding connectors).

 Could be a Compaq SystemPro[1]? Not sure if there was any other 486
multi-CPU machines that were DOS/Windows (single-CPU) and Windows NT
compatible (IE ruling out Sequent Symmetry).
 

It didn't look particularly like either of those (at least, was not a SystemPro; didn't look anything like that).
I don't remember what it was (if I did, would make it easier to look up).
 From what I remember, case was around the height of a tower case, but around twice as wide, and much the front had a whole lot of side-by-side 5.25" bays (mostly unused) (IIRC, the top part had lights/buttons and maybe a text LCD screen).
I don't remember the exact color of the case, my memory is drifting towards a sort of a brownish color.
If anything, at least the Sequent Symmetry was closer in terms of case color, but very different in terms of the front of the case, but dunno...
Actually:
https://commons.m.wikimedia.org/wiki/File:Sequent_Computer_Systems_equipment.jpg
This picture is looking a little closer, just if you pulled the front panel off to reveal a crapton of 5.25 bays, maybe...
Finding more images of the Sequent machines, I think this may be somewhere in the right area, at least in terms of general shape and color. Not a lot of images that I can find. Not yet seen a clear match though.
Though, in this picture:
https://commons.wikimedia.org/wiki/File:Sequent_Computer_Systems_machines.jpg
One on the right is giving the "memory tingles". If the front panel pops off to reveal all the bays behind, very possibly, that particular panel design (with all the horizontal lines) is also looking familiar (like, it being some thin plastic thing that just popped off, like they wanted to hide the drive bays for some reason).
My memory mostly just has directly exposed 5.25 bays though.
So, effectively, the CPU card was around twice the height of an ISA card. Some of its other cards were also extra tall, though the brackets for the cards were the usual size.
I think it may have been EISA connectors for all the cards, just with an extended part. My memory is fuzzy to whether it was ISA or EISA, do remember either way that normal 16-bit ISA cards did at least fit in the slots.
Found a listing for a "vaguely similar looking" MOBO/backplane:
   https://www.ebay.com/itm/126151370449
Though, I think I remember the extended part being present on pretty much all of the card slots (rather than just one of them).
But, yeah, this was apparently something that my mom grabbed from a dumpster sometime around 20-25 years ago, and its fate was that parents later returned it to a dumpster.
IIRC, there was no sound-card in the thing, which was an annoyance, and I couldn't get a normal soundcard to work.

The daughtercard method isn't restricted to these, IBM used it a lot
on their high-end PS/2 and I've seen it used by someone on pretty much
every generation after, back in the days it wasn't uncommon to run out
of space on the main motherboard.
 

Yeah.
The main motherboard in this case, was from what I remember, pretty much entirely card slots and a power connector. More like some of the "passive backplane" boards.

 

It was a weird machine, I had managed to get Win NT4 installed on it,
but I remember I couldn't do much else with it at the time. Also for
some unknown reason, while normal 16-bit ISA cards would plug into the
slots, they did not seem to be recognized by the OS.

 If it was an original SystemPro they appear to be A-SMP (due to being
designed around the '386) so not everything can run on the "second"
CPU, perhaps that what you remember?
 The SystemPro XL appears to be Compaq's first full ("real") SMP 486
machine, this too appears to have leaned into using daughtercards.
This should behave more like a "normal" multi-socket machine.
 Both may well be "first" - Compaq was really leading the field at this
point.
 1. https://en.wikipedia.org/wiki/Compaq_SystemPro

I don't remember if the second CPU was visible.
I think, once I got NT4 installed, that it may have only seen the first CPU. At least, NT4 mostly did NT4 things.
I vaguely remember that DOS (or Win9X) didn't really work at all on it.
Like, NT4 being pretty much the only thing I could get to install on it (and do useful things, like being able to see that the HDD existed; I think the Win9X installer just couldn't see the HDD or something, which roadblocked installation pretty fast).
...