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
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<cr1901_modern>
(6:04:32 PM) ***cr1901_modern contemplates starting on a personal project. His first one in months <-- Well, that went absolutely nowhere. How's _your_ personal project coming along, ej5?
<ej5>
which one
<cr1901_modern>
the MCA card
<ej5>
so the guy who sent me the photos of the MCA adlib says it doesn't work in his model 80. and now i know why
<ej5>
the timings don't match up, the YM3812 is too slow for the MCA bus in his model 80.
<ej5>
it *should* work in my model 50 which has a 300ns I/O bus cycle time. but the model 80 has a 175ns cycle time!
<cr1901_modern>
ahhh interesting
<ej5>
well technically 200ns
<cr1901_modern>
This sounds analogous to the problem w/ early ISA
<ej5>
i guess the folks at ad lib didn't do all the engineering work to get MCA to work on all the machines
<ej5>
because the model 80 was already out when they were working on the card.
<cr1901_modern>
AIUI, on 8088 and 286 machines, ISA clock was synchronous to the CPU clock, up to 25MHz in the most extreme case. Then 386 and above chipsets pinned it to 8MHz (or 4.77MHz, I forget). I wonder if IBM made the same mistake with MCA?
<ej5>
they did not, MCA could run pretty fast
<ej5>
i think the peripheral makers messed up and assumed it wouldn't run that fast
<cr1901_modern>
Damnit you're making me want to spend money (I don't have!)
<cr1901_modern>
to get an MCA machine and some cards
<ej5>
what ad lib should have done was use the extended asynchronous cycle which would have automatically added wait states
<cr1901_modern>
Oh, you no longer need a 74HC daughterboard?
<cr1901_modern>
ej5: Tyvm
<cr1901_modern>
whitequark ^^ (whoops)
<whitequark>
cr1901_modern: absolutely not
<ej5>
there are mistakes on those schematics fyi
<whitequark>
revC interfaces with floppies directly
<whitequark>
no pullups, no buffers
<whitequark>
it's pretty neat how it works with anything from "floppies from 1980s" to "latest intel eSPI horror from 2010s"
<cr1901_modern>
mmm what level shifters are used? I want to check the datasheet. Because my first attempt at doing TTL interfacing on floppies, even w/ a level shifter (some HC part?) sincerely did not work due to sink problems.
<cr1901_modern>
I mean, if it works it works :P. Just surprised
<whitequark>
SN74LVC1T45
<whitequark>
I've specifically designed it to operate correctly with TTL levels
<whitequark>
it's not a coincidence
<whitequark>
we looked at the shifter impedance, inline resistors, and the TTL specs
<whitequark>
it's not *completely* in-spec in that if you have a really huge TTL fanout it might go outside of the allowed zones, but it seems unlikely for any reasonable use
<whitequark>
and it's certainly in-spec for floppies
<cr1901_modern>
It says 32mA. Guess that's enough
<whitequark>
it's more complex than that bc you have to consider the complete IOB impedance
<whitequark>
but anyway
<whitequark>
also, those shifters are monstrous
<whitequark>
they can dissipate a *watt* for a *day* with no visible degradation of silicon
<whitequark>
have you seen SOT-563? it's smaller than a matchhead.
<whitequark>
considerably.
<whitequark>
in fact, it's so small, it's the single finest pitch component on the board, including the BGAs...
<TD-Linux>
the SN74LVC1T45 is excellent
<TD-Linux>
I'm using the wider variants on GlasgISA
<TD-Linux>
and use them on midiori and cbus-joystick as well
<andlabs>
SN74LVC1T45
<andlabs>
can the 74xx series part numbers get any more nonsensical
<TD-Linux>
it's not 74xx. it's TI
<whitequark>
yeah the only real problem with it is it's too fucking small
<andlabs>
yes, and TI created the 74xx series
<cr1901_modern>
SN is TI's code
<cr1901_modern>
LVC- Low Voltage CMOS
<whitequark>
oh wait, LVC1T45 *does* come in sane packages
<whitequark>
oh it comes in WLCSP too.
<whitequark>
clearly we should have used that.
<whitequark>
for maximum photosensitivity
<whitequark>
*flash* the board explodes
<TD-Linux>
whitequark, yeah it comes in nice packages. the 8T variants comes in ezpz SOIC
<cr1901_modern>
Grepping for SOT-563 in the datasheet returns nothing
<cr1901_modern>
not that means much
<whitequark>
page 27
<andlabs>
the SN7400 quad NAND gate was so wildly successful that TI just reused SN74 as the prefix for their other logic chips
<whitequark>
they call it SC70
<andlabs>
and other manufacturers started cloning these logic chips to create the 74xx ecosystem
<andlabs>
I wonder which is more resilient nowadays, the 54xx or the 74xx
<andlabs>
(ceramic cap or plastic cap)
<cr1901_modern>
Only the 1T45 is weird to me. But the "1" is called e.g. "8" on the equivalent part w/ 8 ports
<cr1901_modern>
T45- who knows?
<cr1901_modern>
Sorry, it's called 8T245*
<whitequark>
T is for tristate i htink
<cr1901_modern>
so my guess is TI wanted to derive a proper level shifter from the 245, which can also be used as a limited level shifter. And then tacked on some extra codes to synthesize a new 7400-series family member
<cr1901_modern>
Ack re: tristate
* cr1901_modern
needs a _modern_ TTL handbook. For modern people. Bastardizing retro hardware.
andlabs has quit [Quit: My MacBook has gone to sleep. ZZZzzz…]
<cr1901_modern>
andlabs I think 5400 is milit- oh, he's gone
<emily>
seriously I'm pretty sure the stable recommended interface to flac for basic encoding/decoding tasks is the command line :p
<emily>
like it's how other tools use flac IME
<whitequark>
this makes me not like flac a lot.
<whitequark>
i should just encode to mp3
<emily>
i mean, same with LAME?
<whitequark>
ok let me rephrase
<whitequark>
i fucking hate audio
<cr1901_modern>
that's normal
<emily>
gosh
<emily>
just write your own flac encoder
<emily>
how hard can it be
<emily>
glasgow is going to grow one eventually i'm sure
<whitequark>
;w;
<cr1901_modern>
compression is annoying
<emily>
you can do it in gateware!
<emily>
that actually sounds fun
<cr1901_modern>
and the flac spec expects you to be an expert in iyt
<whitequark>
compression in gateware is VERY hard.
<cr1901_modern>
btw, whitequark, that link is beautiful
<whitequark>
i'm pretty sure this FPGA isn't even remotely large enough
<emily>
oh, yeah
<emily>
i guess decoding is way easier
<cr1901_modern>
I sometimes link one of the more popular streamers of this type in here; there is a popular genre of Twitch streaming where one takes games, randomly changes bytes in the .text/.data sections, and then observes the results. It's called "ROM corruption". >>
<cr1901_modern>
FM music driver .text of FM parameter .data corruptions are absolutely hilarious/beautiful to me when done right. I think overclocking is a new genre
<whitequark>
lol
<emily>
whitequark: btw if you feel this way about audio i can't *imagine* what your feelings on video are
<whitequark>
emily: video doesn't exist. end of story
<cr1901_modern>
One of my favorite is when one of the channels is modified to play slower, so the whole tune slowly goes out of sync- it's like the poor OPN chip is trying, but the bassist/drummer was drunk.