ChanServ changed the topic of ##yamahasynths to: Channel dedicated to questions and discussion of Yamaha FM Synthesizer internals and corresponding REing. Discussion of synthesis methods similar to the Yamaha line of chips, Sound Blasters + clones, PCM chips like RF5C68, and CD theory of operation are also on-topic. Channel logs: https://freenode.irclog.whitequark.org/~h~yamahasynths
* andlabs|2
connects gewt to a Geniac
<andlabs|2>
also on the subject of typefaces
<andlabs|2>
Pietro Gagliardi, [01.05.21 20:53] looking at other listings from someone seleling an MSX printer
<cr1901_modern>
Which CRC16 do IBM PC floppies use again? Does it invert the first part of the data bits/append ones to avoid the "CRC can't tell whether leading/trailing zeros were added/removed" problem?
<cr1901_modern>
I _finally_ understand the CRC Wikipedia page, the "Mathematics of cyclic redundancy checks" Wikipedia page, and now I get my ass kicked by the "Computation of cyclic redundancy checks" page
<cr1901_modern>
"You know all that stuff we were talking about on the first two page? Yea well, real world CRC calculators don't do that, so here's all the real world complications, go fuck yourself".
<andlabs|2>
oh
<andlabs|2>
I forgot
<andlabs|2>
er
<andlabs|2>
I didn't forget
<andlabs|2>
I was wondering, I thought you were talking about CRCs in a mathematical sense
<andlabs|2>
but I guess not
<andlabs|2>
did you watch ben eater's videos on CRCs?
<cr1901_modern>
No, and I don
<cr1901_modern>
t want to, really. And well, I've been learning about "why CRCs work" and ran into a snag
<cr1901_modern>
CRCs are based on polynomial division in base-2 modular arithmetic (no carries, addition is the same as subtraction which is the same as XOR operator)
<cr1901_modern>
Prepending zeros to your data, even unintentionally, has the same remainder as your data will if you _didn't_ prepend the zeros
<cr1901_modern>
(Because e.g. 00000001001 and 1001 are the same polynomial)
<cr1901_modern>
Same with appending zeros (I think? I need to check)
<cr1901_modern>
There are tricks to catching these cases that I'm trying to grok, my question is "does IBM PC floppy CRC uses these tricks?"
<cr1901_modern>
(preset and post-invert)
<cr1901_modern>
And my follow-up: Why is this important to catch? Aren't you keeping a running tally of "bits processed" in the case of a floppy? And in other protocols, won't they flag an error if the number of bits processed isn't a multiple of 8 before the in-band "end of data" marker comes in?
<andlabs|2>
https://www.ebay.com/itm/184806831283 today's book cover: the IDEA BOOK one (have to link to this auction because amazingly no pics on google image search despite having an ISBN and multiple copies for sale on various sites; also interesting because it's the author's collection)
<andlabs|2>
cr1901_modern: I don't know but I do know in ben's videos he links to some website which catalogs a bunch of crc variants
<andlabs|2>
let me get the exact link
<andlabs|2>
users.ece.cmu.edu/~koopman/crc
<fseidel>
I've heard some fun stories about Phil Koopman, he apparently got very aggravated about the CRC polynomial used for ethernet because he found one that's more optimal... or something
<fseidel>
not sure on the specifics
<andlabs|2>
also apparently invlaid CRCs are used for copy protection
<andlabs|2>
Sierra in particular is named by this first result I found looking for a straight answer to your question
<andlabs|2>
the datasheet doesn't say what crc it uses
<andlabs|2>
the dataseheet also says soemthing about "IBM compatibility" though
<cr1901_modern>
IBM System 34
<andlabs|2>
which makes me incredibly suspicious
<andlabs|2>
oh
<cr1901_modern>
This is mostly a case of "I used to know, but forgot the specifics"
<andlabs|2>
that's something that always annoyed me about checksums, btw
<andlabs|2>
people not saying what the checksum algorithm is and just taking it for granted
<andlabs|2>
BSDs have a checksum command that implements its own weird checksums that absolutely no one uses which makes it useless and you might as well write your own routine if you need to do non-cyclic checksums
<andlabs|2>
"An operator sat in front of a device that vaguely resembles today's PC, except the monitor was small, expensive (US$2,000), low-resolution (24x80) and the available colors were green and bright green."
<andlabs|2>
today's wikipedia quote
<Foone>
the only colors you need are green and MORE GREEN
<Foone>
although a fun thing about how it works is that because of how it's on/off + intensity, technically you have green, bright green, black, and bright black.
<Foone>
which ends up being just black.
<andlabs|2>
I'm always amused by implementations of intensity that do that for some reason
<andlabs|2>
I'm too used to the CGA palette which doesn't and has two levels of black
<cr1901_modern>
Okay I think I remember now re: how to determine the floppy CRC: IBM 3740 is the original FM floppy format. There is a CRC known as "crc-16/ibm-3740" in databases- CCITT-FALSE, explaining the "incorrect" comment.
<cr1901_modern>
Since System/34 MFM is the spiritual successor, the designers used the same polynomial for MFM as well (360kB disks)
<Lord_Nightmare>
does someone make a carboard computer case kit?
<Lord_Nightmare>
to be honest, if you use double-walled thick cardboard like what they ship lab chemical containers in, it should be pretty damn durable
<Lord_Nightmare>
it will LOOK ridiculous unless it gets printed/painted to look cool
<Lord_Nightmare>
and it has the advantage of being fully and easily recyclable
<Lord_Nightmare>
at least insofar that paper is recyclable and biodegradable
<Sarayan>
EMI?
<Lord_Nightmare>
hmm. aluminum foil stapled to the inside, maybe?
<Lord_Nightmare>
"At frequencies from 30 to 100 MHz, aluminum foil provides at least 85 dB of shielding effectiveness."
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<gewt>
got outbid on my 4th language translator/tutor lol
<gewt>
it exceeded my fun budget so i'm not continuing to bid
<andlabs>
oh people actually do want these now? okay
<andlabs>
🙄 can we go back to ivory towers of one person ever being interested in something please
<gewt>
i miiiight be the reason they're getting more expensive
<gewt>
lmao
<gewt>
having bought 3
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<Foone>
I wonder how many things on ebay cost more just because of our household
<Foone>
like, the price of VideoFloppy cameras got mentioned in an LGR episode, and it turns out that was because I WAS BUYING THEM ALL
<andlabs>
lol
<andlabs>
I know you and Clint know each other, did you tell him that? =P
<Foone>
yeah, I apologized on twitter, I think
<andlabs>
heh
<andlabs>
now I wonder what *I've* driven up
<andlabs>
I know ther eare entire classes of things I'm trying to get my hands on for various reasons
<Foone>
I was more sorry about that time he heard about a weird computer on reddit (because I posted about it), bought two, and neither worked properly
<andlabs>
and yeah that's another thing I'm starting to worry about
<andlabs>
not only that soon all retro tech collectors will be rich white guys
<andlabs>
but that soon all retro tech collectors will be rich white guys with extreme hardware repair expertise
<Foone>
it definitely seems to be moving in that direction, yeah.
<andlabs>
that latter point is a limiting factor for me :D
<andlabs>
I know my father does all the soldering and he doesn't feel comfortable touching surface-mounted components so I still need to send my CD32 in for recapping
<andlabs>
but the person I found who offers that service hasn't replied to email yet
<cr1901_modern>
andlabs: Contact OhPoorPup on Twitter for recapping. I'll vouch for her
<Foone>
I'm halfway in that direction, being a white not-guy who isn't rich but isn't poor anymore either, who can occasionally fix things
<andlabs>
exactly!
<andlabs>
that's where I am, though I am more firmly guy (but only "mostly")
<Foone>
yeah. gender is hard let's go shopping
<andlabs>
cr1901_modern: cool; ftr the person I was trying to contact was retrohacks.net
<andlabs>
...and I think I figured out why I never heard back
<andlabs>
though I'm not sure why I didn't get an "unknown address" postmaster bounce
<andlabs>
maybe gmail doesn't sned those?
<cr1901_modern>
Well, Idk if Christa/OhPoorPup has done CD32, but she's done nice Game Gear, N64 recaps.
<andlabs>
my CD32 problem is very odd
<cr1901_modern>
I'm guessing she'll figure it out quickly if she hasn't. I would've sent her my Virtual Boy if she did mods back when I needed it
<andlabs>
even out of s-video I seem to have no blue channel
<andlabs>
so everything's tinted yellow
<andlabs>
(not quite the same as LGR's industrial monitor that has a bad blue cap)
<andlabs>
actually I was going to say that that was just that seller being stubborn
<andlabs>
but
<andlabs>
*because they've been relisting it and it hasn't been selling
<andlabs>
but now I'm seeing a bunch of other people doing similar things
<gewt>
my IPX ended up in pieces and lost some time back due to an emergency move :(
<Foone>
there's somebody doing the relist-10$ cheaper game on craigslist near me with a PS/2 desktop. last I saw they were down to 110$
<Foone>
I'm tempted but only at like 30$, maybe 40$
<andlabs>
actually two specific sellers
<andlabs>
some people just will not get it
<andlabs>
there's a selaed copy of double dragon 3 for genesis going on ebay that the seller has been trying to move for $10,000
<Foone>
two people selling something no one wants at that price is the worst
<andlabs>
sorry but that is never going to sell at that price
<Foone>
because they both think the other justifies the price
<andlabs>
it's not even graded!
<Foone>
I'll grade it for them. you get a D- in selling things
<andlabs>
my favorite is when I get a seller ebay automated offer from them and it's like $50
<andlabs>
lol
<andlabs>
at some point I will be tempted to just make an offer for $100 instead
<andlabs>
*$50 off
<Foone>
I think there's a kinda-shady thing some sellers do where they have multiple storefronts. like either ebay and another site, or ebay and a brick-and-mortar
<andlabs>
(one of?) Nerionaya's gfs complained on one of her streams about the prices of DOS gaming PCs skyrocketing
<Foone>
and they intentionally overprice it on ebay because they don't actually expect to sell it there
<Foone>
but they list it for like 2X price just in case someone really wants it
<andlabs>
they now bought that one PS/2 with a gas plasma display
<andlabs>
I forget the model name
<Foone>
mmm, gas plasma
<andlabs>
likewise I am frustrated by Tandy 1000s becoming overpriced now
<Foone>
I really need to get one of my plasma displays working
<andlabs>
in fact all non-CoCo Tandy computers are skyrocketing
<andlabs>
I had to give in and buy a Model I for $175 because I knew I wasn't going to get a better deal ever again; the prices are skyrocketing *as we speak*
<andlabs>
five months ago they were all under $100
<andlabs>
the Model I is a computer I have no potential use for
<Foone>
I don't think that one is my fault. though I do think I own one of each Tandy 1000
<andlabs>
I'm not too interested in buying DOS PCs from the early 1990s though
<andlabs>
other than the Tandy ones because of the exclusive modes
<andlabs>
I still have all of mine from when I was a kid in the attic and I'd rather revive those
<Foone>
the Tandy 1000s are interesting because they're not really PCs. They're PCjrs!
<andlabs>
SPEAKING OF THINGS JUMPING IN PRICE
<andlabs>
the pcjr is finally cool !!!
<andlabs>
it's no more compatible with most PC software than it was in 1984 but it's cool now for some reason
<Foone>
I blame Mike Brutman.
<Foone>
he's been working on convincing everyone it's cool since... well since it came out, probably
<andlabs>
someone listed this and it was bought instantly
<andlabs>
that was a lucky deal
<andlabs>
especially for one of the rarer models
<cr1901_modern>
He also thinks highly of the AT and was great help in getting mine up and running in Dec 2010. He also has a good DOS TCP/IP stack
<andlabs>
(yes, a computer without a disk drive in 1984 in the US market! I wonder why it flopped...)
<Foone>
yeah. he was the co-organizer of the VCF:PNW I went to, and I didn't realize it was the same guy until the very end
<andlabs>
I still want to go to VCF at some point
<Foone>
I was finishing packing up and went "wait, I know that name. why do I know that name?" and had to go back in and confirm it was him and shake his hand
<andlabs>
the closest I've come to VCF was attending a Talks at Google talk by the guy who's building a software emulator for the ENIAC