33 votes

Late 1970s and 6502 chip facilities for operating systems

The simple answer is that early operating systems for the systems you mention did not provide those features. Apple DOS, for example, makes no use of interrupts, and has no concept of processes or ...
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  • 9,956
29 votes
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Late 1970s and 6502 chip facilities for operating systems

For "home" computer systems such as the Apple II, the "operating system" wasn't anything like a modern one with processes and device drivers and so on; by the standards of modern ...
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  • 21.9k
26 votes
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Could you manually eject a floppy quick enough to prevent data loss?

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, ...
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  • 21.9k
18 votes

Late 1970s and 6502 chip facilities for operating systems

We talk about the late 1970s and mainstream 6502 machines, right? It wasn't so much that programs run under OS control as that OS was a support function to Programs. More like what we would today ...
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  • 173k
17 votes

Apple II: DOS 3.3 Virus?

I am one of the two authors of Killer DOS. If you know the final lock screen when your disk was corrupted, we took credit as "The Master" and "The Wizard". I was the DOS Master. We were high school ...
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16 votes

Could you manually eject a floppy quick enough to prevent data loss?

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 ...
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  • 9,956
15 votes
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How many versions of DOS were there for the Apple II and what were the differences?

There was no public release of DOS 1 or 2. DOS 3.1 was actually the first release to the public. It had a pretty significant bug in its MASTER CREATE program, and so the patched version DOS 3.2 was ...
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  • 1,029
14 votes

Was Apple DOS 3.3 created because of the Apple III?

No, conversion to 16-sector format (and the necessary change from DOS 3.2 to DOS 3.3) was a consequence of Steven Wozniak realizing that he could get more capacity by tweaking the Apple II floppy ...
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  • 21.9k
13 votes

Late 1970s and 6502 chip facilities for operating systems

The typical circa-1980 8-bit CPU provided almost no support for modern operating system features. It was often possible to add such support using external logic, but very few machines actually did so ...
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  • 16.1k
13 votes
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Apple II: DOS 3.3 Virus?

What you're looking for is called Killer DOS, which behaved exactly like the Unnamed First Virus described on the Apple II History Viruses page. Killer DOS may have been the second version described ...
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  • 633
13 votes
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Was Apple DOS 3.3 created because of the Apple III?

TL;DR: No, not really. It was even more twisted. 16 sector was done for the Pascal System for the Apple II, independently and before the Apple III got it, but didn't get rolled out for DOS until after ...
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  • 173k
10 votes

Late 1970s and 6502 chip facilities for operating systems

Contemporary operating systems for the 6502 did not have those features. But not because they couldn't. It just wasn't considered necessary or desirable. Provide automatic switching between ...
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  • 5,813
9 votes

Apple II: What type of partition tables were used?

ProDOS provides a common device driver API for storage systems, but does not specify a partition table format. Rather, the SCSI (or other) HD interface card has firmware to map partitions to ProDOS ...
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9 votes
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Was the ProDOS beep part of the kernel or just a commonly duplicated piece of code?

It is a programming convention (i.e. copied code), not part of ProDOS. ProDOS 8 Technical Reference Manual 5.4 Programming Conventions The standard Apple II "Air-raid" bell has been ...
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8 votes

Apple II / ProDOS: Run binary games without BASIC.SYSTEM?

First off, the direct answer to your question is "Yes", you can run some DOS 3.3 binary games without loading ProDOS BASIC.SYSTEM. However, it isn't quite as simple as that. Second point is that it ...
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8 votes
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Apple II: ProDOS partitions on floppy disks?

ProDOS supports up to 2 storage device volumes per slot, but does not support partitioning within those volumes. It is a function of the firmware provided with the storage device controller (i.e. SCSI ...
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7 votes
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How could a 16-sector PROM Apple II access a 13-sector disk?

Does it bypass the 16-sector PROMs? Like MUFFIN it got it's own RWTS. How exactly does it work and why does it work on the 16-sector PROM upgraded interface? Because DOS 3.2 also got it's own ...
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  • 173k
7 votes

Why did Apple remove booting from external drives in later IIc ROM versions?

Whilst this is not a definitive answer, by looking at Apple IIc ROM Version1, which more fully lists the features of each ROM version, it seems that the disk support was actually improved, whilst, ...
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  • 1,817
5 votes

Apple II / ProDOS: Run binary games without BASIC.SYSTEM?

The correct answer is, of course, "It depends". ; - ) If the game loads lower than $800 or is multiple files or otherwise tries to use DOS, work is needed. Otherwise use Bitsy Bye and MiniBas in ...
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5 votes
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Converting Apple II ProDOS blocks to DOS tracks and sectors

DOS-ordered images were created by DOS programs that started reading from track 0 sector 0, continued to sector 15, moved to track 1 sector 0, and so on until the end of the disk. They are in DOS ...
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  • 7,591
4 votes
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How to transfer file from one disk to another in Apple //e (Applewin)

You should download and use CiderPress which is a Swiss Army Knife tool for Apple disk images - It understands and supports the UCSD Pascal file system format and should be able to transfer a file ...
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  • 28.4k
4 votes

Where did the "LEVI" file selector/runner for the Apple II DOS 3.3 come from?

I did some looking around on the internet archive, browsing through a few collections, and I ran across this variant: Rhode Island Apple Group Volume 14 - Integer Basic Games The disk contains a ...
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  • 8,456
4 votes
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Where did the "LEVI" file selector/runner for the Apple II DOS 3.3 come from?

The program appears as "HELLO AUTO SELECT" in various public domain software collections that seem to derive from 1981 or earlier. This name appears in The Public Domain Exchange disk 166: "Hello and ...
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3 votes

Late 1970s and 6502 chip facilities for operating systems

I have done this with an 8051, (8 bit running about same speed as 6502) with a 4 task scheduler, driven by interrupts, task switching at about 10Hz. Reading position from NMEA on a GPS, sending and ...
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3 votes

Late 1970s and 6502 chip facilities for operating systems

The specific details of what a 6502 Apple II was doing when it was sitting at the BASIC command prompt or Monitor command prompt is this: Periodically check for a keyboard key press to be detected at ...
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  • 3,491
3 votes

Apple II: ProDOS partitions on floppy disks?

You can't create partitions with arbitrary contents, but programs like Glen Bredon's DOS MASTER allow you to have multiple DOS 3.3 volumes on a ProDOS volume, including 3.5" disks and hard drives. I ...
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  • 7,591
2 votes

How many versions of DOS were there for the Apple II and what were the differences?

There were also two other formats common on the Apple ][: Pascal and CP/M. Though the latter required a special Z80 CP/M card (such as the Microsoft Softcard), the former was proprietary to the UCSD ...
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  • 14.3k
2 votes

Why did Apple remove booting from external drives in later IIc ROM versions?

Short Answer: Not just ROM code, but as well I/O space is a premium and unlike ROM size it can't be increased. There are only 7 slots and only 7 devices can be present (*1) and accessed (*2). When ...
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  • 173k
2 votes

Late 1970s and 6502 chip facilities for operating systems

it doesn't seem clear to me how the operating system protects itself on the 6502 or PDP-11. With respect to the PDP-11: it's pretty conventional. In general, there are at least 2 execution modes (...
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  • 28.3k
2 votes

Could you manually eject a floppy quick enough to prevent data loss?

As a former floppy disc repair technician, you can indeed do this, but you risk damaging the read-write heads and/or the alignment of the heads, rendering the drive unusable until it is repaired or ...
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