SoylentNews is people
SoylentNews
Submitted via IRC for Bytram
How did MS-DOS decide that two seconds was the amount of time to keep the floppy disk cache valid?
MS-DOS 2.0 contained a disk read cache, but not a disk write cache. Disk read caches are important because they avoid having to re-read data from the disk. And you can invalidate the read cache when the volume is unmounted.
But wait, you don't unmount floppy drives. You just take them out.
IBM PC floppy disk drives of this era did not have lockable doors. You could open the drive door and yank the floppy disk at any time. The specification had provisions for reporting whether the floppy drive door was open, but IBM didn't implement that part of the specification because it saved them a NAND gate. Hardware vendors will do anything to save a penny.
[...] Mark Zbikowski led the MS-DOS 2.0 project, and he sat down with a stopwatch while Aaron Reynolds and Chris Peters tried to swap floppy disks on an IBM PC as fast as they could.
They couldn't do it under two seconds.
So the MS-DOS cache validity was set to two seconds. If two disk accesses occurred within two seconds of each other, the second one would assume that the cached values were still good.
I don't know if the modern two-second cache flush policy is a direct descendant of this original office competition, but I like to think there's some connection.
(Score: 2) by RS3 on Thursday September 26 2019, @03:12AM (6 children)
BTW, not sure if you still run any MacOS Classic machines, but one interesting site: https://www.macintoshrepository.org/ [macintoshrepository.org]
(Score: 2) by DannyB on Thursday September 26 2019, @02:35PM (5 children)
That's cool. I've long since moved on. I look back fondly at those days. I probably would still be interested in that up until about ten years ago.
To transfer files: right-click on file, pick Copy. Unplug mouse, plug mouse into other computer. Right-click, paste.
(Score: 2) by RS3 on Friday September 27 2019, @01:49AM (4 children)
Ah, but wait, I have, in writing, you admitting coveting a Beige G3! I have one! It can be yours! I had even bought a speedup CPU for it (I forget the name but you'd know it...) I have a dual G4 MDD!! That too can be yours!!
(Score: 2) by DannyB on Friday September 27 2019, @03:10PM (3 children)
> Ah, but wait, I have, in writing, you admitting coveting a Beige G3!
Really? I don't seem to recall that.
I have a gray G3. Collecting dust. But last known to be working. It's a desktop style box with a monitor on top of it.
To transfer files: right-click on file, pick Copy. Unplug mouse, plug mouse into other computer. Right-click, paste.
(Score: 2) by RS3 on Saturday September 28 2019, @01:30AM (2 children)
> Really? I don't seem to recall that.
Okay, you win. But you were thinking it.
I'm pretty sure my Beige G3 is the same as your gray one. Pretty cool machine. I liked the interior layout- very efficient, compact. I modded the HD mounting so I could put up to 4 HDs in it. I had a Macintosh PCI IDE (ATAPI) controller. I can't remember when I last booted it, but it should still boot. Last time might have been 5 years ago to read some older Mac formatted floppies. I miss the boot chime. Yeah, I could download it, but it's way cooler when it's from a booting Mac.
(Score: 2) by DannyB on Monday September 30 2019, @03:50PM (1 child)
The interior layout of later Macs like these, and also of the 1983 Lisa, was amazing.
Without a single tool, just your bare hands, you could open up the machine and access any and everything.
PC's in contrast, required tools to open. And tools once you got inside. And further, I swear that PC manufacturers must have paid a staff of people to sharpen all of the edges on the inside of the case to ensure you would cut your bare hands bloody.
To transfer files: right-click on file, pick Copy. Unplug mouse, plug mouse into other computer. Right-click, paste.
(Score: 2) by RS3 on Tuesday October 01 2019, @02:36AM
I never saw inside a Lisa, but overall I always thought Macs were designed, not cobbled. Some, like my MDD, require screwdrivers to remove hard disks.
Dell started doing tool-less cases, for the most part, and with fairly well marked release tabs, etc. Others followed suit.
> And further, I swear that PC manufacturers must have paid a staff of people to sharpen all of the edges on the inside of the case to ensure you would cut your bare hands bloody.
They had, let's call it, a special working relationship with a secret medical organization. ;-}
But seriously, one of my biggest pet peeves in life is sharp metal edges. GRRRRR!!!!!!! I literally think there should be a law, and I've felt that way since childhood.
I love when they fold sheetmetal back on itself rather than leave sharp edges, and again, newer machines have finally been doing that, esp. Dells.