107 votes
Accepted

On DOS computers, what would the PARK command do?

Hard drives have read/write heads which fly above the spinning disks when the drive is powered. When power is removed, the heads no longer fly... For a long time now, the arms which hold the heads ...
Stephen Kitt's user avatar
64 votes

Apocryphal (?) tale of hard drive platter propelled through a wall?

Some "informed speculation" based on my "day job" which involves worrying about containment of rotating objects if they break (specifically, rotating parts inside jet engines) The rotating parts of ...
alephzero's user avatar
  • 6,646
50 votes

Why were floppy disks invented after hard disks?

Floppy disks are harder to get right than hard disks. Early hard disks were enormous; the IBM 350 used fifty 24-inch platters. They were also rather fragile and cumbersome (heavy and power-hungry). To ...
Stephen Kitt's user avatar
49 votes
Accepted

Why were optical drives not used as secondary storage instead of magnetic drives?

For the simple reason that until relatively recently, it was very difficult to make a rewritable optical medium, but it was easy to make a rewritable magnetic medium. Magnetic tape as a recording ...
Chromatix's user avatar
  • 16.8k
45 votes
Accepted

Why was computer memory so expensive and scarce?

As noted in some initial comments (but I feel fine answering, as I had the exact same ideas when I read the question), this is a general progression of technology but there are two very specific ...
manassehkatz-Moving 2 Codidact's user avatar
41 votes

How did it come that SATA HDDs use ATA while SATA CD drives use SCSI as protocol?

Let’s start by addressing a few misconceptions. I have a new external Western Digital USB HDD here and I saw in Wireshark that it uses SCSI. That’s because storage over USB uses SCSI-style protocols....
Stephen Kitt's user avatar
40 votes
Accepted

Why were floppy disks invented after hard disks?

While Stephen Kitt's answer already hits the core, I believe it needs a bit more history, as direct access magnetic storage did start quite a while before the IBM 350. Drums and Disks First there were ...
Raffzahn's user avatar
  • 218k
37 votes
Accepted

Why do hard drives not use larger platter sizes anymore?

My question is if you can fit X number of tracks on a 3.5" platter, why not use the same density on a 5 1/4 platter and have even more tracks? I know there are tradeoffs like latency due to head-...
Raffzahn's user avatar
  • 218k
36 votes
Accepted

How much did the first hard drives for PCs cost?

I looked at trade periodicals from the time in question, because the intended customer for a hard drive in the early 1980's was almost certainly a business or school (look at the prices, particularly ...
ErikF's user avatar
  • 1,921
33 votes

Is it possible to limit HDD capacity to work on an old computer?

Since the price seems to be an issue, I'll suggest a cheap alternative to hard drives. A IDE Compact Flash card reader with a 4GB or 8GB compact flash card is a cheap combo, still sold (less than 10 ...
Jean-François Fabre's user avatar
28 votes

Did mechanical hard drives often malfunction in high elevation places such as Bogota?

Most modern hard disk drives are not pressurised. They have a "breather" hole (normally with an air filter) to let the internal and external air pressures equalise. They're normally rated to ...
John Dallman's user avatar
27 votes

Why were optical drives not used as secondary storage instead of magnetic drives?

Write speed and endurance. Optical drive technology has been much slower to write to than magnetic Hard Disk Drives (HDDs). The erasable optical technologies that made it to mass market were much ...
TonyM's user avatar
  • 3,658
27 votes

Why was computer memory so expensive and scarce?

I'm mostly concerned about RAM. Why was it so expensive? It wasn't - at least not once integrated circuit RAM became available in the 1970s. Compared to other chips, RAM was cheaper both per ...
Bruce Abbott's user avatar
  • 6,653
27 votes

Did something like floppy disk jukeboxes for home computers exist in the 70s or 80s? Would that have been a feasible concept?

There was a product, called I think "Juke Box 5" designed for the Macintosh, which had a hopper on the top that could hold a IIRC about 20 floppies, and was designed to be placed in front of ...
supercat's user avatar
  • 35.7k
26 votes
Accepted

How does Windows 9x determine which disk drivers correspond to which BIOS disks/DOS drive letters?

By their contents. When Windows boots, the I/O Supervisor VxD (IOS) uses BIOS interrupt 0x13 services to read sector 0 (the Master Boot Record) of each drive. It then looks at two bytes at offset ...
user3840170's user avatar
  • 22.8k
26 votes
Accepted

When was the CHS (cylinder - head - sector) system invented and what was before it?

It seems the question is mixing up physical disk access (CHS) with a logical access scheme used at a higher level. LBA is and always has been an issue at the OS level. The fact that some disk ...
Raffzahn's user avatar
  • 218k
25 votes

What were the early PC applications requiring a hard disk?

I cannot state for certain that it required a hard disk, but using AutoCAD (v1 released Dec.82) without one would have been awkward to well-nigh unbearable. The program itself was huge for the time ...
RichF's user avatar
  • 8,761
23 votes
Accepted

Apocryphal (?) tale of hard drive platter propelled through a wall?

There is also this tale that I read recounted in Philip and Alex's Guide to Web Publishing, although the disk pack was intentionally hurled through the wall in a fit of temper: That night, the ...
Samper Williams III's user avatar
22 votes
Accepted

Can a stock/original Atari ST boot from a hard drive?

All models of the Atari ST1 had code in ROM to attempt to read and run a boot sector from the first sector an ACSI2-attached drive. The bootloader3 contained in that sector would4 load the hard disk ...
Alex Hajnal's user avatar
  • 9,320
21 votes
Accepted

Did something like floppy disk jukeboxes for home computers exist in the 70s or 80s? Would that have been a feasible concept?

Many home computers in the 1970s and 1980s had two floppy disk drives Home computers had any number of drives from zero to 6 or 8, all depending on budget. Even rather restricted systems like a C64 ...
Raffzahn's user avatar
  • 218k
21 votes

Do/did mechanical hard drives constantly spin the discs?

Yes, mechanical disk drives are constantly spinning, for two reasons: First, the wear and tear on the motor and drive is much bigger during spin-up and spin-down than when running at a constant speed. ...
tofro's user avatar
  • 34k
20 votes

How much did the first hard drives for PCs cost?

TL;DR: How much did the first hard drives for the IBM PC or Apple || cost, and how big were they? Ready to use setups started around 3,000+ USD for 5 MiB in 1981 Long (Hi-)Story As usual defining '...
Raffzahn's user avatar
  • 218k
19 votes
Accepted

What were the early PC applications requiring a hard disk?

I started working for a newly-certified IBM PC dealer in the UK at the end of 1984. IBM thought we would be selling about 50% twin-floppy PC (PCG) and 50% XT with 10MB hard drive. In fact, I'm not ...
grahamj42's user avatar
  • 1,162
19 votes
Accepted

Default (as opposed to physical) read/write heads - what are they?

The physical geometry how many heads the drive actually has is not the same as the logical geometry of how many heads is presented to the PC by the drive. By translating the geometry, the drive can be ...
Justme's user avatar
  • 30.4k
18 votes
Accepted

How can I take an image of a 50-pin SCSI hard-drive

If "a more modern machine" includes systems with ISA, PCI or PCI Express slots, it should be easy enough to retrieve the data from the drives. You'll need a SCSI adapter (known as a host bus adapter, ...
Stephen Kitt's user avatar
18 votes
Accepted

Getting data from Seagate ST-238R drive

The ST-238R shown in the image is an RLL (Run Length Limited) drive and will not work correctly with a standard MFM controller, although it has the same ST506 electrical interface and cabling. To read ...
StarCat's user avatar
  • 1,475
18 votes
Accepted

Was there ever a Linux kernel driver for accessing disks via BIOS?

At first, I was convinced that such a driver had never been written. But in fact, there was one; although it was never merged into upstream Linux. Thanks to @Joshua for pointing me to it. The driver ...
user3840170's user avatar
  • 22.8k
17 votes

Is it possible to limit HDD capacity to work on an old computer?

I have not tried it, but according to the Wikipedia page on the Host Protected Area, one use case was to use large disks on systems whose BIOS could not cope with them. It would therefore seem to be a ...
pndc's user avatar
  • 10.9k

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