remember my post about bowling computers? I learned some shit
a friend advised me that he used to work on a brunswick system, mid 90s era, and sent me the service manual for it. now, this isn't the era i was really interested in (late 80s, early 90s) but it's still some fun data. it used a set of "Lane Servers," beige 486 towers running windows and some very Visual Basic-ass software; each server could support eight lanes.
ever wonder how pins are detected so the system can score automatically? well, that's a whole rabbithole that I might talk about later, since there's actually been a ton of approaches over the years. it's actually a really tough problem! most places you can mount a sensor system where it won't get destroyed by wayward balls/pins will be unable to see the entire field because some pins will be shadowed by others, but this particular system was able to make it work by very carefully positioning a camera mounted to the lane bumper.
the image above really tells the whole story - that crosshair icon comes with visual studio. they're just slurping up frames from the camera and looking at a single pixel to detect the pins. you have to manually type in the brightness level it should look for. no ML horseshit. this probably works flawlessly except when it doesn't
now, how do they get the camera feeds?

multichannel capture card. this ran on a 486, and the card is ISA, so my guess is that the FPGAs are there to decode the signal and compress it so four (or as many as eight; not sure why this isn't fully populated) channels of video can fit across the bus. nothing more to it - the "machine vision" is clearly being done in software since they're only looking at a single pixel
how about all the I/O? there has to be gobs of it - surely each lane has like 60 little 22ga wires in a bundle (if you're lucky) that run to the back, where do those all terminate?

huge fuckoff multiport serial card, natch. the keyboards, pinsetters, lane sensors, cameras and overhead displays all plug in on this back panel. presumably the first two categories are all serial interfaces that terminate onto this custom I/O card. the camera inputs are just plain composite, natch. the overhead monitors are interesting.
one of my big open questions is: when did they start having the overhead display play Agony Of Defeat clips when you roll a gutterball, and how does that work? my guess is that it started in about 1995, just early enough that it wasn't really economical to do it in any reasonable way, so they probably had a bank of laserdisc players that were switched into the monitor feed with some complicated elevator algorithm nonsense where you had to wait like 4 seconds for your stupid video to play if someone elses lane was busy humiliating them
well, this does nothing like that, and maybe nothing like that ever happened. maybe this is how it was done from the get go

this is obvs the most interesting component of the whole thing. speculating on how it works
there are eight lanes worth of circuitry, each with an FPGA, a RAM chip, and what I assume is a DAC. my guess is that this is very straightforward: when a lane needs to play a video, the software pushes it to the card over the bus, storing it in the RAM for that lane, and once it's loaded, the FPGA decodes it and the DAC turns it into analog video
The rest of the time, the overhead monitor is displaying the score. This part is interesting to me. Since the output from this DAC is wired to the port on the back of the machine, then this has to be where the scoreboard picture comes from. But do they generate that in software and send it to the card as a bitmap, or do they send bytes to the FPGA and it assembles the bitmap itself? Maybe it doesn't assemble the bitmap, and just races the beam. I think this is the most interesting part of the whole machine and I will never know how it works.
this was phenomenally expensive in the 486 era but i can't think of a better way to do it, and for a system that probably cost, idk, $150,000 at least? it seems reasonable.
so yeah that's it. as far as i can tell, it really is no more complex than that. it's a normal PC with two cards that are pretty much just high-density versions of shit you could buy off the shelf, and then one special video player. the TVs were off the shelf monitors that brunswick rebadged, per the manual. the software is the most bland, visual basic ass shit, there are only a couple pictures but it looks like 14 year old me designed it. it really is as MVP as it could possibly be.
i would still be very interested to see how the pre-windows-95-era stuff worked. i think that's probably a lot more intriguing, but probably 100% of it is in the garbage
