4 ms·

side select.. so.. that basically flips between upper or lower read/write heads.. That wire though.. It seems they could have gotten twice the speed by having

by dusted 3y ago

side select.. so.. that basically flips between upper or lower read/write heads.. That wire though.. It seems they could have gotten twice the speed by having two read and two write pins, one one additional pin.

zaxomi 3y ago
The first floppy from 1967 only had one side. Adding one signal to select side was an easy solution to increase the capacity without to much modification of the controller. Adding the capability to read from both heads at the same time would require much more modifications, and more memory.
- FullyFunctional 3y ago
  Undeniably true; so much of computing hardware (and software) looks archaic and bizarre because it's the process of a long chain of backwards compatible changes (don't get me started on ATAPI). But that aside, like dusted I too wonder just _how_ hard it would have been for a company like, say Apple, to demand the extra circuit. Might not have been worth it for just 2X speedup. Now I want to build a 10X floppy RAID ...
  - MBCook 3y ago
    Everyone had that extra circuit in the floppy controller, it was just somewhere else. Ask for it to be integrated and now you go from being able to buy drive from almost anyone to only one vendor. It is odd it never improved and stayed as simple as it was until the end of floppies. The power of history I guess.
MBCook 3y ago
Yeah, but then you need twice the CPU cycles to encode/decode it. And that may have been the limiting factor when first introduced. After that it’s all backwards compatibility. No one wants a new interface. I remember the first time I saw a floppy pin out, I was dumbfounded. I expected it to be far more complex like IDE. I didn’t realize the term “floppy controller” would be so literal. Of course in retrospect it makes sense. IDE = Integrated Drive Electronics. I assume the hard disks that came before worked more like the floppy and their controllers did more work too. I guess no one cared enough to enhance the poor floppy drive until we got to things like LS-120 that I assume flat out couldn’t use the old interface and never took off anyway.
- kalleboo 3y ago
  > I assume the hard disks that came before worked more like the floppy and their controllers did more work too. You nailed it. The first hard disk interfaces for IBM PCs were basically identical to the floppy disk controller just faster/bigger. https://en.wikipedia.org/wiki/ST506/ST412 https://en.wikipedia.org/wiki/ST506/ST412 The ST506 interface between the controller and drive was derived from the Shugart Associates SA1000 interface,[5] which was in turn based upon the floppy disk drive interface,[6] thereby making disk controller design relatively easy But as they started wanting to make disk reads faster and faster, the drive part had to get smarter and smarter The ST412 disk drive, among other improvements, added buffered seek capability to the interface. In this mode, the controller can send STEP pulses to the drive as fast as it can receive them, without having to wait for the mechanism to settle. An onboard microprocessor in the drive then moves the mechanism to the desired track as fast as possible At that point the drive is starting to getting smart enough that you might as well integrate the whole controller on there. The original versions of IDE/ATA were basically just an extension of ISA, and the first "IDE cards" were just a bridge to the ISA slot they went in. You also had "hard cards" where the hard disk itself was integrated onto the ISA card... https://en.wikipedia.org/wiki/Hardcard https://en.wikipedia.org/wiki/Hardcard

by dusted 3y ago

zaxomi 3y ago

The first floppy from 1967 only had one side. Adding one signal to select side was an easy solution to increase the capacity without to much modification of the controller. Adding the capability to read from both heads at the same time would require much more modifications, and more memory.

FullyFunctional 3y ago
Undeniably true; so much of computing hardware (and software) looks archaic and bizarre because it's the process of a long chain of backwards compatible changes (don't get me started on ATAPI). But that aside, like dusted I too wonder just _how_ hard it would have been for a company like, say Apple, to demand the extra circuit. Might not have been worth it for just 2X speedup. Now I want to build a 10X floppy RAID ...
- MBCook 3y ago
  Everyone had that extra circuit in the floppy controller, it was just somewhere else. Ask for it to be integrated and now you go from being able to buy drive from almost anyone to only one vendor. It is odd it never improved and stayed as simple as it was until the end of floppies. The power of history I guess.

MBCook 3y ago

Yeah, but then you need twice the CPU cycles to encode/decode it. And that may have been the limiting factor when first introduced. After that it’s all backwards compatibility. No one wants a new interface. I remember the first time I saw a floppy pin out, I was dumbfounded. I expected it to be far more complex like IDE. I didn’t realize the term “floppy controller” would be so literal. Of course in retrospect it makes sense. IDE = Integrated Drive Electronics. I assume the hard disks that came before worked more like the floppy and their controllers did more work too. I guess no one cared enough to enhance the poor floppy drive until we got to things like LS-120 that I assume flat out couldn’t use the old interface and never took off anyway.

kalleboo 3y ago
> I assume the hard disks that came before worked more like the floppy and their controllers did more work too. You nailed it. The first hard disk interfaces for IBM PCs were basically identical to the floppy disk controller just faster/bigger. https://en.wikipedia.org/wiki/ST506/ST412 https://en.wikipedia.org/wiki/ST506/ST412 The ST506 interface between the controller and drive was derived from the Shugart Associates SA1000 interface,[5] which was in turn based upon the floppy disk drive interface,[6] thereby making disk controller design relatively easy But as they started wanting to make disk reads faster and faster, the drive part had to get smarter and smarter The ST412 disk drive, among other improvements, added buffered seek capability to the interface. In this mode, the controller can send STEP pulses to the drive as fast as it can receive them, without having to wait for the mechanism to settle. An onboard microprocessor in the drive then moves the mechanism to the desired track as fast as possible At that point the drive is starting to getting smart enough that you might as well integrate the whole controller on there. The original versions of IDE/ATA were basically just an extension of ISA, and the first "IDE cards" were just a bridge to the ISA slot they went in. You also had "hard cards" where the hard disk itself was integrated onto the ISA card... https://en.wikipedia.org/wiki/Hardcard https://en.wikipedia.org/wiki/Hardcard