Apple 2 Floppy Disk Codes - Computerphile

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Steve Wozniak got creative with the Apple ][ floppy drive, creating a system that used less complicated hardware and was cheaper, accomplishing much in software instead. Dr Steve Bagley explains.
The graphic showing where sector holes were read is incorrect. Sector hole was seen where Dr Bagley showed. Earlier 8 inch floppy disks had different standards for hard sector disks, some at the hub, some near the outside of the disk- which is what the graphic was trying to illustrate.
Rob Miles on Game Playing AI: • AI's Game Playing Chal...
Musical Floppy Drives: • Musical Floppy Drives ...
Magnetic Media (Floppies and Tapes): • Magnetic Media (Floppi...
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This video was filmed and edited by Sean Riley.
Computer Science at the University of Nottingham: bit.ly/nottscomputer
Computerphile is a sister project to Brady Haran's Numberphile. More at www.bradyharan.com

Опубликовано:

6 июн 2016

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Комментарии : 170

@bobwashburn7791 8 лет назад

Back in July 1978, as I was leaving Data General, Westborough MA, to lead the Apple distributing company, Larry Seligman, DG's top computer designer (he designed the Supernova 16 bit minicomputer), told me how impressed he was with the minimalist design that Woz had done on the DOS hardware controller. Larry was a thesis away from his MIT PHD, gave high praise to a UC Berkeley dropout at the time.

@Mew178 8 лет назад

And once again we see who the real genius behind Apple actually was.

@TheMikkelOLaursen 8 лет назад

Well, the real technological and engineering genius. But that is not enough - he needed Jobs to make it a product and a success. But it's often the man in the spotlight that gets all of the credit; the guy(s) behind the scenes is easily overlooked.

@Remmes 8 лет назад

They both were, without either of them it wouldn't have been a success. They pretty much needed each other.

@UnknownGunslinger 8 лет назад

+Remco Smit you are very correct!

@rooneye 8 лет назад

What Woz did thought was much greater of an achievement and deserves far more respect. Not to downplay the marketing nous of Jobs though, for sure Apple wouldn't (and weren't when he wasn't there) have been such a huge company.

@rooneye 8 лет назад

Richard Dale You're missing the point... It's not that Jobs wasn't needed, it's that inventing this stuff through brilliant engineering is harder/more impressive/greater achievement than being able to sell/market it. The people who market and sell shitty products are more of a marketing "genius" than Jobs (remember Pet Rocks? A guy literally found a way to market and sell rocks!) it's a lot easier to market/sell a great product that was created by a brilliant engineer.

@StevenWeyhrich 8 лет назад

Part of the genius of Woz's design was that he eliminated the electronics that used that timing hole, and did the syncing via software, as you said. You could put a piece of tape over that hole and an Apple II floppy would still work.

@jamesslick4790 8 лет назад

This design was pure genius, It also explains why I saw many more Apple ][s with FDDs in the early "home computer" era, Almost everyone else put up with Cassettes. On many early "home computers" the FDD often exceeded the price of the whole rest of the set-up!

@thoughtyness 8 лет назад

Steve was very helpful to Apple. He envisioned the products and their design, but Wozniak was the true genius.

@KuraIthys 8 лет назад

mmh. Wozniak. The true legend of Apple. Also, stiffies. Lol. I remember hearing about that...

@IMortage 8 лет назад

Every story about the beginnings of Apple seem to go like "Wozniak does some genius stuff because he has fun doing it and Steve Jobs recognizes how valuable it is and sells it to somebody/the public."

@Ben-fx9kx 8 лет назад

+IMortage Maybe because it's true...

@DrRChandra 8 лет назад

A little extra information for the interested: Using a sequence which is not legal to find in the middle of payload data is fairly common in storage and communications systems, called a "preamble." When the preamble pattern goes by the receiver or read head, the circuit "knows" it's the beginning of something, like a sector or frame. It can be implemented in very high speed hardware with a shift register and logic gates. The logic gates are wired in the pattern of the preamble, and constantly compare the value in the shift register with the preamble...and the output goes "true" when they match. Then the circuitry can begin collecting the bits of the payload.

@Slithy 8 лет назад

Ah, the days when Apple products were actually worth their price.

@menachemsalomon 8 лет назад

I remember seeing that modern disks use a similar pattern. Something like 8 bits encoded in a series of 15 pits and lands on a CD. I don't remember the exact numbers, but I'm sure they'll be in the next video. Much appreciated this. Keep 'em coming, +Computerphile.

@hanelyp1 8 лет назад

CDs use an error correction coding such that a single bit error within the set describing a byte can be corrected. Important when the media is unprotected and vulnerable to scratching.

@julesverne6287 8 лет назад

call the police, he's storing cp on his floppies :P

@anonimenkolbas1305 8 лет назад

I was gonna post the same thing, but I noticed someone else had beat me to it.

@noahhounshel104 8 лет назад

"Modern floppies" :P

@wattage 8 лет назад

Great topic and explanation. Love hearing about the genius of Woz and other pioneers. Please keep the vids like this coming. Loved it!

@DasIllu 8 лет назад

I remember GCR was also used in the Commodore floppy drives back in the days. It was a real pain in the rear end to transfer data between MFM-coded systems like IBM or Kaypro and the Commodore family. In the end i found my self soldering a little pcb with some transistors and resistors and hook up those systems directly via parallel port. Big plan was to use e decommissioned 286 board as "hard drive controler" for my beloved C=128. Never completly finished it though. But i used it for cross assembler stuff.

@iseslc 8 лет назад

old tech is so much more interesting than new one!

@NeilRieck 8 лет назад

It's been a while since I read "Beneath Apple DOS" but IIRC, 5-and-3 encoding supported 13 sectors per disk (Apple DOS 3.2) while 6-and-2 encoding supported 16 sectors per disk (Apple DOS 3.3). I recall taking my Apple ][ to a local retailer to have the floppy controller updated from 3.2 to 3.3 (IIRC they just replaced a ROM). After that you could deal with 3.3 formatted disks natively or run a small utility which would allow you to read 3.2 disks. There also existed many copy-protection schemes based upon partially written tracks as well as data written between tracks. Many people got around this (for backup purposes only) with a utility call Locksmith.

@ewlloyd 8 лет назад

Steve implied that the index hole was used by the disk ][ hardware to find Sector 0 -- it was not. Woz didn't use the index hole for anything at all. In fact, had the index hole been used, it would've made it impossible for third-party formatters to optimize the disk. They worked by staggering the zero sector of adjacent tracks to reduce the number of total revolutions needed to read the disk sequentially. Oh, and the sectors were laid out on each track non-sequentially so the RWTS routine had enough time between sectors to process the data it had read.

@ScottLahteine 8 лет назад

I once had to write custom floppy read/write routines for the Amiga. On that system you could use the "blitter" to do the encoding and decoding. I believe it used "Modified Frequency Modulation" (MFM) for the encoding system.

@UnknownGunslinger 8 лет назад

This is the best explanation Ive ever heard!

@AntoineVignau 8 лет назад

At 3:30, there is a wrong statement. You can have two consecutive zeroes (the nibble shown here, #$9F is an authorized value) but no more. This is rule #2. As with rule #1 (nibbles start with bit 7 at 1), these can be bypassed to create interesting on-disk protection schemes.

@IONYVDFC 6 месяцев назад

The 16-sector version PROM on the DISKII interface indeed allows 2 consecutive zeroes, which provides 81 combinations respecting rule #1 and #2 in an 8-bit range. From these 81 combinations (~6.34 bits), only 6 bits are retained, or 64 combinations. The GCR encoding on 16-sector disks actually costs 1.34 bits per byte, that is 20.75% data loss, the simplest error-correction encoding algorithm (HAMMING 29,24) costs 1.66 bits per byte or 17.24% and could theoretically replace rule #2. The only problem is that rotation timing issues due to having more than 2 subsequent zeroes is likely to mess up much more data than the error correction encoding itself can remediate.

@wisteela 8 лет назад

Cool to see an Archimedes A310 with twin floppy drives. I've got one like that, and had never seen another one.

@hwrdmltn 6 лет назад

Yea, except that what he failed to say was that GCR does not use the index hole, or the track 0 sensor - it is completely soft sectored and software controlled. That's why the head banged in C64 and Apples - step 50 tracks back and your guaranteed to be at track zero sooner or later........

@StonedAvocado 8 лет назад

CP >>__>>

@anderson1134 8 лет назад

Track 2: Sector 2: Felonious

@BREDCLAN 8 лет назад

computer phile u perv

@Stigsnake5 8 лет назад

It is only a reflection of yourself.

@SNMG7664 8 лет назад

that's what I thought of too, of all of the letter combinations he could've used that had to be the one that came to mind -_-

@StereoBucket 8 лет назад

Dennis Fluttershy, they obviously meant Cartoon Pony

@bighugejake 8 лет назад

You should do a video on encoding techniques for data reading/writing. I know there is Manchester and 4B/5B for data communications but what about Gigabit and 10 Gigabit speeds and their encoding methods?

@IONYVDFC 6 месяцев назад

After disassembling the Apple II Disk rom (the 16-sector version however) to check the GCR encoding, I discovered that the first 32 bytes of ROM code actually builds this lookup table counting 64 distinct values. So, on each byte written on a 16-sector disk, the first bit is always 1, and the remaining 7 bits make 64 combinations where the rule applies of max. 2 consecutive zeroes. This rule theoretically allows 81 combinations across 7 bits, but understandably only 64 were retained for the lookup table. So, from each byte, only 6 bits materialise in usable data.

@kay486 8 лет назад

the camerawork on this one was especially atrocious

@DeciduousClouds 8 лет назад

i read this and thought "oh its not That bad" before immediately scrolling up to see 0:50

@zxb995511 8 лет назад

That beeping when the machine booted on.....all the nostalgia....

@ChristopherdeVilliers 8 лет назад

Yes in South Africa they were called Stiffy Disks. And USB memory sticks are sometimes called a Stokkie

@nixdorfbrazil 8 лет назад

I remember when I had to use the other side (apple drives had just one head), we had to punch a hole on the floppy jacket in order to make the drive to read it properly when we flipped the disk. Also, disks weren't designed to be flipped, and with time you had problems with disks that were flipped, as the fibers inside the jacked got sticky with dust. Nostalgia! :)

@wotsac 8 лет назад

That hole wasn't about readability. The notch would turn on write protect when it was covered. On the flipped over side, there was no notch, so the computer would treat the disk as write protected until you punched that hole.

@JimFortune 8 лет назад

The disk factories only had one production line. The disks that wouldn't certify on either side were thrown away. The few that would certify on one side and not the other went into the pile of single sided disks, and the ones that certified on both sides got split up between the single and double sided disk piles according to demand. We used thousands of cheaper "single sided" disks as double sided and every now and then had to throw one away.

@JimFortune 8 лет назад

@carelvanheerden101 8 лет назад

True, here in South Africa we call them floppies (5¼-inch) and stiffys 3½-inch... The good old days...

@Elesario 8 лет назад

What a coincidence. ;)

@rooneye 8 лет назад

Shouldn't it be the other way around? ...Oh wait, we're not talking about penises, oops! xP

@pieterpohl1991 8 лет назад

As a South African, I'm embarrassed to admit I thought it was called floppy's and stiffies everywhere in the world. I mean, the one is really floppy, and the other really stiff in comparison.

@jmp01a24 7 лет назад

Pieter I would think that is how any oldskoolers would define it. It got confused and hence you get word salads like what we see today: people don't know how to use the terms.

@brettbreet 8 лет назад

I've always wanted to know how Epyx Fastload for the Commodore 64 worked!

@TheRoboticLlama 8 лет назад

Back in my day, if you had a 3.5 inch floppy, you would have to hope no one found out

@naota3k 8 лет назад

rofl. I have to say, 3.5" floppy is pretty impressive. I'M A GROWER, NOT A SHOWER. LOL

@rich1051414 8 лет назад

+naota3k Isn't that a Seinfeld quote?

@jmp01a24 7 лет назад

3.5"" disks - not floppy. To be a floppy disk it had to be 5 1/4"" or larger. Thin and not in hard plastic like the 3.5"". Hence the word floppy.

@rich1051414 7 лет назад

Don't speak of things you do not know. 3.5'' were still called floppies... Kids...

@sideburn 6 лет назад

If you had a computer you would have to hope no one found out!

@salvatoreshiggerino6810 8 лет назад

4:58 \things\don't click\cp\cp

@TheSpacecraftX 8 лет назад

Uh. "Lets use the file 'cp'"... ... Lets not.

@DanDart 8 лет назад

so meta! if you cp cp, whither do you cp cp?

@cheatmagnet 8 лет назад

Care to explain why though?

@TheSpacecraftX 8 лет назад

cheatmagnet cp is internet slang for ch1ld pr0/\/. Cause once you say it straight you're for sure on a list. See also "cheese pizza".

@TheSpacecraftX 8 лет назад

Ze Rubenator Yes but there is unlikely to be a cerebral palsy file on a sketchy floppy disk is there. It's the context.

@TheSpacecraftX 8 лет назад

Ze Rubenator That's ridiculous. How many acronyms do you know of off the top of your head that are cp? Very few people likely know that cerebral palsy has that acronym while many people who have spent any time on the internet know the other one. And then you take into account the context and even if you know other acronyms for cp, as long as you know the pr0n one it makes most sense. If you know that JPG means "Joint Planning Group" and somebody says lets look at this JPG file, do you assume they mean the image format or a section of the Department of Defence?

@isuckatlifemutechannel6050 8 лет назад

Continental pizza on a floppy? Wonderful now we made technology edible

@clangerbasher 8 лет назад

The first floppy I bought was for use with an Apple ][ It cost me 5 pounds. PR#6

@clangerbasher 8 лет назад

Moe Bius My face command on the ][ was SPEED. Small things amuse small minds. I remember it taking me 2 nights with a friend to type in a 1k program looking for every key in utrn.

@clangerbasher 8 лет назад

Moe Bius BTW that was a lovely reply. Thanks Moe.

@PvblivsAelivs 8 лет назад

I'm pretty sure that I remember you could encode two consecutive zero bits. I do remember about the index hole not being used and the sectors being synchronized by writing 4 or 5 "FF' bytes with two zero bits between each two bytes. This was done with exact timing of the instructions.

@FozzTexx 8 лет назад

Neither Apple II or C64 used the index holes, that's why you could flip the disks over and use the other side. Using two consecutive zeros was the change from 13-sector to 16-sector disks.

@dogcowdogcow 8 лет назад

What's being described in the video is the earlier 13-sector DOS 3.2 format and the P5/P6 ROMs (and not the 16-sector "at most one zero-bit pair per nibble" 6&2 format of DOS 3.3 with the P5A/P6A ROMs; see Beneath Apple DOS for more detail.)

@PvblivsAelivs 8 лет назад

dogcowdogcow Interestingly, I'm not going by DOS formats at all. I was, for a time, working on my own code to read and write disk data and I was going by the rules to be able to read back what was written reliably.

@DrRChandra 8 лет назад

about the six minute mark...sorry to say, you circled the incorrect area. Holes would show through the small circular area next to the hub.

@Computerphile 8 лет назад

+rchandraonline there were different standards, early hard sector disks had holes in different places to later ones...

@DrRChandra 8 лет назад

***** , hmmm...I had both hard sectored and soft sectored 5.25" floppies in my time, and I can't remember any of them having holes in the read/write area which you circled, only in the area Steve pointed out to you. The soft sectored ones had one index hole for a "start of track" signal, whereas the hard sectored ones had several holes around the circumference of the hub. But who knows, there could have been others I have not seen.

@Computerphile 8 лет назад

+rchandraonline it's possible that these were just in the eight inch variety and I have muddled up my image! Sorry (Wikipedia : "The Memorex disk was "hard-sectored", that is, it contained 8 sector holes (plus one index hole) at the outer diameter (outside data track 00) ")

@Seegalgalguntijak 8 лет назад

With all the hard sector holes in the center, how would the disk drive then know which sector was the first one?

@DrRChandra 8 лет назад

Seegal Galguntijak , IIRC, on a totally blank disk, the controller just picked one, and wrote a track preamble there. It was either that, or one of the holes was larger and therefore let through more light. It was when I was in high school, back in the late '70s, early '80s, when I remember both hard and soft sector disks were available...so taxing my memory you are.

@titaniumdiveknife 8 лет назад

MOAR!!!!!!!!!!

@ShiroKage009 8 лет назад

It only flips the magnetic field when it needs to write a 1? How dose it know that this was flipped? It could be either or. I thought it flipped it to a specific orientation that encoded either a 0 or a 1.

@thesaurus1523 8 лет назад

You're right, the animation is wrong.

@AntoineVignau 8 лет назад

The presenter is right. On the Apple II, you store a 1 by changing the state of the magnetic field, otherwise it is a 0. What is missing here is the description of the Logic State Sequencer which sequences the bits, the timing and the state change. The LSS is responsible for transforming the 1s and 0s into nibbles.

@ShiroKage009 8 лет назад

Antoine Vignau Could you please simplify that a little? I'm still not getting how the system knows that you've flipped this bit when it could be either a 0 or a 1.

@ImSquiggs 6 лет назад

Couldn't you check the state of the previous bit? If it doesn't match then it was flipped.

@BunnyFett 8 лет назад

My favorite speaker.

@BryonLape 6 лет назад

Woz was a pure genius, but I sure wish he hadn't compromised high res graphics so much.

@thromboid 6 лет назад

By the mid-1980s, Apple II graphics did look pretty terrible, it's true - but in 1977, colour graphics of any sort were pretty much unheard of and were apparently a major selling point of the machine. Even a built-in keyboard was unusual for microcomputers at the time.

@BryonLape 6 лет назад

Agreed. It seems odd to say, but the popularity of the Apple ][ was its biggest fault. Both Commodore and Atari created computers based on the 6502 with more capability, but the Apple ][ outlasted them all. The IIGS demonstrated just how difficult it was to move onward.

@jacknedry3925 4 года назад

Bryon Lape, Apple should have focused on the IIGS, it’s superior than the Macintosh in MANY ways.

@CommanderMouse72 6 лет назад

Nowadays if you were talking about a 5.25 inch floppy they'd think it meant something completely different

@cptfwiffo 8 лет назад

So, we're encoding and thus 'losing' 30% of our capacity for speed ? (we're having 8 flops, and use that to store 5 bits)

@moebius435 8 лет назад

GCR is actually more reliable than hard sectoring. With hard sectoring there are more components interacting in more complicated ways. With soft sectoring, you only need the speed of the drive motor to be correct (typically 300 RPM if I recall.)

@edgeeffect 8 лет назад

Couldn't you find a 3D model of a 5.25 inch disc? ;)

@MyAvitech 8 лет назад

Ahh. The boot clicks of the disk drives. It meant that the computer was coming alive. Now when drives click like that, it means its dying and I better rush a backup. My how times change.

@grn1 3 года назад

@LaserActiveGuy In the early 2000's (I'm guessing around 2003 ish but a lot of it's a blur) I couldn't find my library card for the longest time until I went to use the floppy drive on my machine and couldn't get it to work. Turns out one of my siblings (they were all quite young at the time) had put my library card in the floppy drive. At that point we were more worried about whether something was in the CD/DVD SuperMulti drive that every computer came with (I'm guessing they were really cheap since absolutely every computer seemed to have the exact same one).

@blacklistnr1 8 лет назад

Hey video edit guy, remember how a while ago a top comment was a complaint about a high-pitched buzzing(~15.6kHz)? Well it's still there making the video uncomfortable to watch. So..yeah..

@hamzaelouakili2438 8 лет назад

Have you turned it off and on again. Who gets the reference?

@Blutnase 7 лет назад

The IT Crowd

@jameselmore1780 8 лет назад

Computerphile should do something about net neutrality

@hanniffydinn6019 8 лет назад

Woz === genius !

@MichaelPohoreski 7 лет назад

@5:41 NO! Apple 2 sectors were **NEVER** hard-sectored --they were always SOFT-sector. That index hole was NEVER used. The ADDRESS field D5 AA 96 .. DE AA EB recorded held which Track and Sector the head was over, the DATA field, D5 AA AD .. DE AA EB held the **342** nibble data for the sector.

@15743_Hertz 4 года назад

Which one had the **420** nibble data? Did I just ask a question? Whatever...

@tubemaster567 8 лет назад

Modern floppies? Is there such a thing?

@Seegalgalguntijak 8 лет назад

So basically, these disk drives stored 5 bits in the amount of data it would take to store 8 bits, but have these three "parity bits" as a safety feature to prevent or correct read/write errors. Did Apple disks have less storage capacity than the ones of other computer systems because of that?

@15743_Hertz 4 года назад

140K (DOS 3.3) per disk side vs 174K (C64), 160K (IBM SSDD).

@otakuribo 8 лет назад

💫 😵 Magic eye effect at 1:12

@sidgar1 8 лет назад

He looks like the Adoring Fan from Oblivion

@endofthelinejoel 8 лет назад

Did Wozniak really invent grouped data recording? I've heard otherwise.

@sbrazenor2 8 лет назад

They mentioned that he 'used' it, but they didn't say that he invented it.

@asgerms 7 лет назад

When people talk about "the other Steve", I allways think about Jobs :)

@izzc2506 8 лет назад

Since my dad is from South Africa, I can confirm the part about stiffies.

@thrillscience 8 лет назад

Apple ][ drives did not look at the index hole! You could cut another write-protect notch and flip the disk over and the drive sensor would have no way of seeing the index hole.

@160rpm 4 года назад

I think the C64 also used GCR

@linkVIII 8 лет назад

watching this I can only think of hsf errors in macs

@TheRoboticLlama 8 лет назад

What exactly are "modern floppies"

@Shyhalu 8 лет назад

Coasters and paperweights.

@MrSlowestD16 8 лет назад

Probably speaking of the 3.5's or zips. That'd be my guess, anyway. Not entirely sure.

@smurfyday 7 лет назад

Wikipedia says 8-in floppies were invented by IBM in 1960s to 1970s. 5.25" popped up c. 1977, and 3.5" in 1983. That was probably like decades of innovations now.

@ARitzCracker 8 лет назад

High pitch stuff is still there...

@vitaplex1 7 лет назад

Arent 8 bits called a nibble

@EebstertheGreat 7 лет назад

8 bits is a byte (in modern terminology, though in older computers, "byte" sometimes referred to a different amount of data; 8 bits can be unambiguously called an "octet"). A nibble is 4 bits.

@vitaplex1 7 лет назад

Oh ok

@15743_Hertz 4 года назад

bit, nibble, byte, chomp and gulp. A "bit" of trivia that you'll have a lot of fun finding on google search. Not too many people know about it and some of them fell out of use prior to ARPANET.

@superdau 8 лет назад

When you need 8 bits to store 5 bits, aren't you wasting almost half of the disk's storage capacity?

@andljoy 8 лет назад

He did not invent GCR.

@tedchirvasiu 8 лет назад

Omg, anyone else hears the sharp noise?

@SupaKoopaTroopa64 8 лет назад

Yes, that's the sound of CRT monitors. thank goodness for LCDs!

@MartijnMcFly 8 лет назад

'modern floppies' ...

@unvergebeneid 8 лет назад

"Stiffy" makes much more sense than "3.5 inch _floppy_ disk" for these things. And let's be honest, "floppy" invites penis jokes already, so why not at least make jokes about the ones that aren't flopping about?

@Azur1al 8 лет назад

honestly i had no idea that people elsewhere called them "3.5 inch floppy disk" its just always been a stiffy

@Azur1al 8 лет назад

um pun unintended

@ethanpoole3443 8 лет назад

In the U.S., at least, the term "floppy" was a reference to the flexible disk media within the diskette (versus a rigid "hard" disk) and not a reference to the diskette casing itself being floppy or stiff, so the term "floppy" was generally used to describe both diskette types. When viewed from the perspective of the actual magnetic media, both diskette types were indeed floppy since the magnetic media was flexible.

@unvergebeneid 8 лет назад

Ethan Poole So you're saying only _hard_ disks deserve to be called "stiffy?" I can't really argue with the logic behind that...

@NoahBarr85 8 лет назад

let's call it anything other than cp actually

@PvPigCreations 8 лет назад

"modern floppies"... yeah...

@Diggnuts 8 лет назад

Did somebody completely forgot how to use camera lighting? This is unwatchable...

@pleasedontwatchthese9593 8 лет назад

If this is unwatchable you will have a hard time looking at 99% of youtube.

@Diggnuts 8 лет назад

PleaseDontWatchThese I do, but there is a difference between unwatchable due to a a simple lack of gear and unwatchable due to utter failure while having a shitload of proper gear.

@pleasedontwatchthese9593 8 лет назад

Diggnuts The video gets the point across just fine. It just does not look nice. I find that ok with an educational video.

@Diggnuts 8 лет назад

PleaseDontWatchThese Did I tell you what you should or should not be "ok" with?

@pleasedontwatchthese9593 8 лет назад

Diggnuts You did not, and neither did I. I'm just stating my opinion about yours. And you are doing the same to me. I see no problem with that.

@tschak909 4 года назад

AARRRRGGGGGHHHHH!!!!!! ok, no. (1) The Disk ][ does NOT use the index sensor. Nor does it have a track zero sensor. (2) The logic for implementing group code recording was implemented as a finite state machine, with the individual inputs and outputs of that state machine encoded on a 256 byte sequencer PROM on the Disk ][ controller card. (3) a MC3470 is used as the read amplifier.

@TheProCactus 8 лет назад

How limiting, And how things have not changed for Crapple.

@sugarfrosted2005 8 лет назад

*headdesk*

@TheProCactus 8 лет назад

sugarfrosted Did you like that one ?

@Cowboy_Kim 8 лет назад

buy a camera light, Jesus

@Trisador9 8 лет назад

omg flagged for CP

@JimFortune 8 лет назад

He did a lousy job on this one. Apple DOS didn't use a hard track start, he didn't even talk about how it would find track zero, you don't need a ROM to read the disk any more than you do to write it, and his explanation of 5-3 encoding didn't explain much.