115

While some floppy drives have a sensor to determine when the head is at the outermost position, the Apple uses four approaches: On startup, it blindly tries to move the head outward about 40 tracks. When the motor hits the end stop it will be unable to move further and will consequently stop. Once the Apple has done this, it will assume the head is at the ...


39

In practice, 5.25" drives equalled or exceeded the capacity of 8" drives when 5.25" floppy drives started using HD media. The Evolution of 5.25" Drive Systems There are only two different recording media that were ever commonly used in floppy drives: the original media (often called "DD") and the later HD media. Note that when ...


32

TL;DR: "Frictionless" Floppies are called Hard Disks (*1), consisting of a hard media platter and a head in distance of the media (flying or otherwise) Floppies are 2D tapes. While slower than tapes, their advantage is in (faster) random access for small data sets. The construction was made to save on tapes. They were never intended for continuous ...


26

I did that all the time on the Apple II. The reason it worked was that some time was needed for the motor to spin up to the correct speed, and that the Disk II didn't really have an "eject" mechanism, but that you could very directly mechanically lift the read-write head from the surface of the disk. That meant that if you were quick enough to lift the ...


23

The maximum is 8309 ($2075) nibbles for track 0. Well, according to a little experiment I did. ; - ) The Disk II uses Constant Angular Velocity standardized by Shugart at 300 RPM. The earlier 8-inch drives were 360 RPM, and since the physical media was the same it's likely that 300 RPM was chosen to increase data density on the smaller disks, and perhaps ...


23

The track identification part is quite simple. Floppy formats are standardized so that there are specifications what is the distance between tracks (e.g. 96 tracks per inch) and what is the position of the tracks from some reference point, so the drive is designed accordingly so that moving the head one step will always step one track, and the heads are ...


19

In my experience, your best bet to read 2M/2MGUI disks is to find an old PC with a built-in floppy controller, and run either DOS (with 2M and 2MGUI) or Linux (with Mtools, which supports 2M formats) to try to read the disks. Even then, some 2M disks will be hard to read — beyond the usual problems with old floppy disks, since 2M formats really push the ...


19

Mode Selection and Switching By default a 1571 always boots up in 1541-mode when detecting the first burst (C128) transfer it switches automatic into 1571-mode. OPEN 1,8,15,"U0>M1":CLOSE 1 will switch 'manual' into 1571-mode. OPEN 1,8,15,"U0>M0":CLOSE 1 switches back to 1541-mode Additional Features in 1541 Mode While the 1571 ...


19

the 810 and 1050 specifically, ran at 288 RPM rather than 300. I can't imagine why this might be, I do believe it was needed to securely store 18 sectors per track while using the WDC1771 at 1 MHz feed by a 6507 at 500 kHz. It might have been a sweet spot for components, with slowing down the drive (zero part cost) enabling some savings. Worth noting that ...


17

The closest thing to a modern laptop that I'm aware of featuring an internal 5 1/4 drive is the Findex of 1979 which had a fairly complete (optionally battery-powered) CP/M computer including a hard-sectored floppy drive, a 40 x 6 plasma display and even a printer in a package of about the size of a (quite large) travel typewriter, weighing 20 pounds. I ...


17

DOSBox only allows absolute sector reads from disk images, as mounted by IMGMOUNT. You can’t use interrupt 0x13, service 0x02 on drives mounted with MOUNT. (To understand that link, note that imageDiskList in DOSBox is only populated by the BOOT and IMGMOUNT commands, not by MOUNT.) The workaround is to use IMGMOUNT: imgmount -t floppy a /path/to/floppy.img


16

Theoretically, yes. The disk needs time to spin up to speed before reading or writing can occur. While it varies between platforms and drives, it's at least a couple hundred milliseconds. That's arguably just enough time to realize you shouldn't have hit enter, and to pop the drive latch. Especially if you subconsciously realize it before you even hit ...


16

It sounds like some blocks on the disk (particularly the ones containing directory information) are okay, but some (containing some file data) are not. This is a data recovery situation. If you boot from a Linux LiveCD (or a flash drive built from one), you should be able to use the ddrescue tool which is designed for exactly this situation. It will find ...


16

According to the 1541 service manual, the device contains power-up and power-down write protection. On power-up, the CPU controls the power to read/write electronics so they are not turned on before CPU is properly running. On power-down, the power to read/write electronics turns off before CPU loses power. That said, of course it is possible that there are ...


15

As so often this depends on your definition of laptop - which is not an exact one either. There where many level of size and weight between a bulky schleppable like a Compaq Portable and a notebook sized computer. And only a few would work well on a lap. I wouldn't consider the T1100 be one of them. Still, with the T1100 as cornerstone, I think the Morrow ...


15

If the definition sought after is very strictly speaking "integrated 5.25 inch floppy" and "battery powered", then I would like to enter the Kaypro II from August 1982: Which is a luggable and has Built In Media: Two 5.25'' SS/DD full-height floppies (190k) Peripherals: 400 KB or 800 KB 5.25'' floppy drives, 10 MB hard disc, ...


15

Why did Sharp choose 5.25" over 3.5"? Why something has 'not' been done will seldom get an easy answer. Often it might be a variation of 'why should they'. When the X68000 was released in 1987, 3.5" drives were well established and used in several other 16 bit machines, such as the Amiga and Atari ST. Well established? Maybe, but still ...


13

In a double-sided drive, there are two heads which are necessarily closely spaced, facing both sides of the thin magnetic-coated disc once it is inserted. The concern would have been that the heads could collide with each other if the drive was jarred. However, the drive designs I'm familiar with have a mechanism to hold the heads and drive spindle away ...


13

A sector is the minimum amount of data you can read from a floppy disk or harddisk. As you've drawn correctly, a sector is part of a track (on a harddisk also called cylinder, because there are many platters with one track, so overall you get a cylinder). One thing you are missing is that some floppy drives and nearly all harddrives have multiple heads, so ...


13

There are a number of devices which can be used to connect a floppy drive to a modern computer. Whether they are appropriate in your case depends on what you’re trying to do... If you want to read and write standard PC floppies (1.44 MiB, perhaps 1.68 MiB; this includes most bootable floppy images), then buying a USB floppy drive will be cheaper than buying ...


12

As far as I can tell, the first edition of the IBM 5150 Technical Reference is the only IBM manual which mentions 45 cylinders. Few Technical References document the FDC, which is where the “45 cylinder” mention appears, but those that do, other than the 5150 first edition, don’t reproduce this — see for example the first edition of the IBM 5160 Technical ...


12

Many USB floppy drives will not read double-density (720 / 800 KB) disks at all. Most that can will only read 720 KB disks formatted for IBM PCs. I am not aware of any standard USB 3.5" drives that can read the 800 KB double-density Mac format. They are unlikely to exist as 800 KB disks as used on the classic Macs use a proprietary on-disk format ...


12

Excerpted from Inside Commodore DOS, page 53 4.6 Sequential File Storage The format of a sequential file is very straightforward. All the sectors, except the last one, look like this: TRACK LINK - SECTOR LINK - 254 BYTES OF DATA Byte Purpose 0 Track of the next block in this file 1 Sector of the next block in this file 2-255 254 bytes ...


12

I don't know about the 1541 in particular, but I have personally lost data by powering off a computer with a diskette in the drive. One problem that could occur, independently of whether you remembered to save your work or, whether the OS finished writing out buffered data, was that somewhere in between the power supply and the read/write head, the power-off ...


11

The short answer is they did it to save money. They could have made the drive behave better when a disk is inserted upside down, but that would have required larger ROM chips to store the firmware or more expensive drives and controllers to detect the problem. As long as it didn't damage the computer such behaviours were considered acceptable to get the ...


11

The obvious answer is that it wasn't designed 'for newbs' but as a general purpose personal computer that would find its way into many homes and businesses as well as educational establishments. Even in the latter, they also had to be suitable for running some fairly advanced software as well as for introductory courses. By the standards of the 70s, when ...


11

If you inserted the disk "upside down" the Apple //e would make a hideous noise like a vacuum cleaner. Not sure what the 'vacuumer sound' should be. could it be that you're refering to the way the drive returns - and calibrates - to track. I would rather describe it as a fast clicking noise over some scratching. Also, there was no different operation ...


11

Apple ][ used an ordinary disk transport and fixed bit-rate in the controller. In order to fit more bits on the outer track it would need to vary the spin rate of the disk so that the controller had time to put the extra bits on. CD drives use variable spin rate, but floppy disks (mostly) use a fixed spin rate (like gramophone records). Early Apple ...


11

Yes, the sector size is software-controlled, to a certain extent. Every FDC command involving sectors or tracks takes the sector size as a parameter. The size is specified as a bit shift applied to 128, so sector sizes are of the form 128 × 2n (usable values go from 128 to 4096 on the original PC; there isn’t enough time to fit an 8KiB sector in a track ...


11

The head gap must be very narrow to be able to make sharp magnetic transitions on the moving magnetic media. It also means the magnetic field does not bulge out too much out from the head so the media must move very near the head. If the gap was larger, it would bulge out more, but be weaker and it could not make sharp transitions on the media, which means ...


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