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a crt is just a write only dram framebuffer

@mothcompute I swear there was a very, VERY early computer that used a CRT as an actual *readable* memory element but I forget where I read about this and I can't remember what computer that was

@techokami @mothcompute I think you're thinking of Williams tube memory, as famously used by the Manchester Baby. (I dragged myself through the entirety of ENIAC in Action and I am ecstatic to be able to share this trivia.)

@techokami @MrDOS oh the way this works makes a *lot* of sense. thats cool

@mothcompute @techokami So many early memory and storage schemes are just... not only technically impressive, but wildly creative. Yeah, no big, just gonna store these bits as sound waves travelling through mercury??? Pass me the program, please, yeah, it's all of those rings embroidered together?????? Modern storage is no less arcane (“we taught sand to remember sixteen different voltage levels!”) but doesn't feel anywhere near as off-the-wall.

@MrDOS @techokami i think the scariest part of what you just said is my computer might be storing nibbles of data as *analog*

@mothcompute @techokami I used to work with a mixed-signals EE whose e-mail signature firmly attested that “Contrary to popular belief, the world is ANALOGUE!” And I mostly try to retain my innocence by forgetting that.

@MrDOS @mothcompute @techokami meanwhile, I'm diving in head-first and snorting all the EMI/SI texts I can get my hands on :D

(it's so true though. not only is it analogue, but everything is high frequency now. that 1kHz clock signal? 300MHz bursts in the frequency domain due to the edge rate!)

@gsuberland @MrDOS @techokami i will have you know that fact is unpleasant and scary

@mothcompute @MrDOS @techokami heh, yup. die shrinks and new FET constructions did it. modern IOs have single-digit nanosecond rise and fall times now, sometimes sub-nanosecond on faster parts, so the dV/dt (and thus dI/dt) has gone through the roof, and bandwidth rocketed up with it. even if you're using "old" logic like 74-series / 4xxx-series, if the ICs themselves were manufactured in the last decade their slew rates go off like a rocket.

@mothcompute @MrDOS @techokami so now we've got all these old 80s/90s board designs where folks just ran 2 layer boards, do whatever you like, traces all over the place, zero thought to transmission line behaviours or return currents, who cares, it's all slow, and nobody ever had any SI or EMI issues! but then you make the exact same board with the exact same part numbers but with die production runs in 2020 and they absolutely *spew* EMI due to modern process nodes being so fast. whoops >_<

the freebsd gamer

@gsuberland @MrDOS @techokami hmm. well i have zero ee experience and one of my project ideas involves recreating a 90s board with (some) new parts so this seems concerning

@mothcompute @MrDOS @techokami go 4 layer, solid ground plane on both inner layers, that'll get you 90% of the way there.

@gsuberland @MrDOS @techokami im staring at an snes again and now quickly realizing like. literally all of these parts are surface mounted

@gsuberland @MrDOS @techokami actually i dont think i can even replace any of these chips probably. though i still have no idea how to design video or audio circuitry so i still might have to worry about noise

@mothcompute @MrDOS @techokami surface mount is not as scary as it looks. get yourself some flux (not the pens, get paste, proper soldering stuff not plumber's flux) and some of those SMD practice kits off AliExpress. tin the iron, flux the board, heat the joint, feed solder in, you'll get the technique pretty quickly.

for analogue video stuff, again the signal/ground/ground/signal stackup will save you a ton of headaches. if you swap layers on a trace, place a ground via near the signal via.

@gsuberland @mothcompute @MrDOS not the pens? I personally prefer using a pen, haven't had any issues with surface mount stuff using one. I use a drag soldering method with a chisel tip.

@techokami @mothcompute @MrDOS I don't like the pens at all, they apply too little flux and tend to dry out fast. I also find that decent flux paste acts to tack parts down for hand soldering.

@gsuberland @mothcompute @MrDOS I just solder two corners to tack the part down, but you're probably doing stuff with very small parts so I can see where a paste would be optimal

@techokami @mothcompute @MrDOS does help more on smaller stuff yeah, but also just flooding the heck out of it with flux helps avoid bridges, form a strong clean bond, get really nice joints, and makes it easier to rework if you mess up. useful to at least have on hand.

I also keep some lifting flux in stock for large part rework. you need to thoroughly clean it post-rework, but you can throw it on a fat connector joint with 40 years worth of oxide layer and it'll flow like new.

@gsuberland @mothcompute @MrDOS Understandable. I really should get a refill on my ChipQuik stuff for lifting <_<

@techokami @mothcompute @MrDOS the lifting stuff I use is from a place that sells BGA reballing supplies. low viscosity, high activity. not expensive either, I think I paid £15-20 for a bottle and it has lasted me a couple of years, and that's after I accidentally left the cap off and a fifth of the bottle leaked out and left a big gooey mess on my desk (that was reeaaaal fun to clean up)

@gsuberland @techokami @mothcompute Plus, how do you get the satisfaction of cleaning the stray flux off your anti-static mat if your flux doesn't leak out of the syringe and get all over everything in the first place?

@gsuberland @MrDOS @techokami i do have a little smd soldering experience but i meant like. i dont think there is a single chip on here i can replace with new parts besides the cic, maybe the composite encoder, and like. capacitors and resistors and stuff

@gsuberland @MrDOS @techokami and the dac actually. but im probably going to leave that alone for now

@mothcompute @MrDOS @techokami ah I gotcha. same issue trying to replicate Amigas and such - lots of custom ASICs, lots of GAL/PAL/CPLD stuff.

@gsuberland @MrDOS @techokami nuts. i totally forgot i have to go looking for a4000 chips at some point too

@mothcompute @MrDOS @techokami time to find your friendly neighbourhood Amiga repair techs! there are two regulars at NOVA Demoparty that run a repair bench at the back of the hall, always good folks to know if you're in the market for spares and repairs.

@gsuberland @mothcompute @MrDOS oh yeah I saw this article linked on hackaday, an interesting read