lyall

@llyall

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lyall @llyall8/27/2023, 7:26 PM

gravis again @cathoderaydude

gravis again @cathoderaydude8/27/2023, 3:25 AM

absolutely fucking reeling at this time: i've just learned that PC CDROM drives and burners can use both CLV (constant linear velocity) or CAV (constant angular velocity) techniques. conceptually, this applies to all rotating media, but I've never heard these concepts discussed in connection with anything except laserdisc. I had no idea they were distinctions within CDROM hardware, i thought every drive had to read every disc the same way to be standards compliant.

one practical effect of this: if this review is to be taken at face value, a 24x CDROM is not necessarily a 24x CDROM. according to their tests, LiteOn's 24X, which uses CAV, started out at 11x and only reached 24x as it neared the outer edge of the disc, while Plextor's CLV drive remained 24x the whole time. incredible! that is exactly the effect you'd expect from CLV, but requires far more precise motor control circuitry; Plextor earned their dime.

i've always thought of CD burning as a completely solved problem, and all burners as equivalent for a given speed. it appears i was mistaken, and that is remarkable to me. i should add that i learned about this while investigating a drive from Creative that has a god damn Turbo button on the front, which i am breaking my back trying to research. cdrom: the untold story

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in reply to @cathoderaydude's post:

@darryl @darryl8/27/2023, 3:27 AM

I definitely remember this being a factor in why I paid extra money for a Plexwriter back in the day

Plum @plumpan8/27/2023, 3:35 AM

god I want a fucking plextor

I thought CAV or CLV was a standards thing? At least for DVD, I was looking that up the other day just to confirm for sure that the PS3's optical drive really did suck THAT bad.

@rotopenguin8/27/2023, 5:56 AM

If you're a video player, you don't want faster data. You just want to be fed one frame per frame, with a constant rate mpeg stream that's coming off of a constant rate media. The PS3 was there as the 1st wave of Blu-Ray players, so it definitely had to do CLV right.

I think that CAV is a matter of having so much signal processing power that the disk data looks like bullets crawling by in The Matrix. You can oversample like mad while the drive motor runs flat-out, and turn all those pits and landings and vibrations into data through sheer DSP willpower.

Good CAV logic would have been useful to the PS3, but I imagine that getting affordable Blu-Ray CLV hardware in video players before HD-DVD could take root was more important. Was there any other market for a "Blu-Ray drive, but not for movies"? The PS3 would be about the only device that wants Blu-Ray for "gimmie the data as fast as you can" instead of smooth data-rates. Sony wasn't about to sell speed-oriented Blu-Ray drives to the competition, and the PC market didn't care. Sooo, the logical thing would be to punt on developing CAV, at least until you're selling enough PS3s to amortize it. And that wouldn't happen until the Cell stops being such a bitch to make.

Plum @plumpan8/27/2023, 7:37 AM

Oh yeah it was the correct decision to make in context, hell if nothing else it was easy to say "these are very new they don't go fast yet" and point back to the bad 'ol days of 1x CD rom drives in consoles (hello neo geo) as precedent. Just still fascinating to me that the existing DVD drive tech was so much faster, we're too used to storage density going hand in hand with transfer speed.

Still very curious if there was any regulation for CAV/CLV or if the speeds were that fakeable of a number.

Xīn Jīn Mèng @xinjinmeng8/27/2023, 3:36 AM

Not to mention the problem of explosions. https://www.nytimes.com/2004/12/11/business/worldbusiness/spinning-out-of-controlrisk-of-cd-explosion.html

SEELE, the Throne of Souls @sleeps-darkly8/27/2023, 4:00 AM

And then these elusive 72x drives

@rotopenguin8/27/2023, 5:10 AM

I hope that with Turbo off, it delivers data at a perfect IBM XT pace.

Rachel Stantz @arjache8/27/2023, 5:54 AM

Wait, so there’s no difference in capacity like there is with CAV vs CLV in laserdisc? They write the same amount of data, just at different speeds?

gravis again @cathoderaydude8/27/2023, 4:47 PM

I haven't heard anything about the mode affecting capacity so I have to assume yes

@JosJuice8/27/2023, 7:15 PM

Yep, same amount of data

~@modulusshift8/27/2023, 1:30 PM

Oh so this isn't floppies where the Mac uses CLV and PC uses CAV and they're incompatible, this is "I burned this on a CAV drive so it took longer and I brought it to my friend's CLV drive and it read faster"?

gravis again @cathoderaydude8/27/2023, 7:41 PM

yes exactly