115
votes
Accepted
Why did the Apple IIe make a hideous noise if you inserted the disk upside down?
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. ...
- 33.9k
100
votes
Accepted
How was it back then in 1984, when the Apple II had color, and the new Macintosh didn't?
I was working in software development at the time, and this wasn't seen as a problem. Colour monitors were expensive and not usually high-quality.
In PC-compatibles, the Colour Graphics Adapter (...
- 11k
55
votes
Accepted
What determines the color of every 8th pixel on the Apple II?
A nice one - and coming up every now or then.
TL;DR
The Apple IIs video logic produces a B&W bitstream at the right frequency to bedazzle an NTSC TV set in a way to make it 'see' colour. The ...
- 207k
45
votes
How was it back then in 1984, when the Apple II had color, and the new Macintosh didn't?
The Mac was designed from the start to be a GUI-based machine so clear, high-resolution graphics were a requirement. At the same time available memory was extremely limited due to cost considerations....
- 9,260
41
votes
Accepted
How did Apple fail to tap the business and scientific markets?
The Apple II was a hobbyist's computer that unexpectedly found a business niche. Apple recognised that niche in its design of 1980's Apple III. Specifically, it thought that the following were ...
- 35.5k
40
votes
How did the Apple II forward binary instructions to the Z80 software card with CPM?
They both shared the same memory so it didn't really forward instructions.
The Z80 card stopped the 6502 running using the DMA signals and the system swapped between the two by writing to $CN00 where ...
- 5,225
37
votes
Accepted
What was the point of Apple Pascal having its own file system?
UCSD Pascal was a product of UCSD - The University of California at San Diego. It was not a product of Apple.
UCSD Pascal was available on a number of machines, including the PDP-11, TI99/4, the BBC ...
- 7,963
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 ...
- 1,911
35
votes
How was it back then in 1984, when the Apple II had color, and the new Macintosh didn't?
I imagine it being a huge downgrade for some, not to have color on the Macintosh. Macintosh games were black and white in the beginning, while Apple II had color.
For back then the whole assumption ...
- 207k
33
votes
Accepted
Apple II: Applesoft BASIC memory management
Managing memory on an Apple II using Applesoft BASIC can be quite complicated, especially for large programs.
A general map of Apple II memory at power-up looks like this:
$E000-FFFF - Monitor ROM / ...
- 3,629
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 ...
- 13.4k
32
votes
Accepted
How does "bit-slip" copy protection work?
The Apple II reads disk tracks as a continuous stream of bits. To make sense of the data, it's necessary to figure out where individual bytes start. This is done with self-sync bytes.
Standard self-...
- 8,605
32
votes
Accepted
How do I use shadowed memory to render Super Hi-Res quickly?
Fast Screen Refresh With PEI Slamming
(Or: Dirty Tricks With the Direct Page)
This article is based on my KansasFest 2004 presentation "Code Secrets of Wolf 3D."
Introduction
Drawing super ...
- 958
31
votes
Accepted
Over its lifetime, how many Apple II computers were sold?
Apple has not released sales figures for their early systems, so your question cannot be answered accurately. I will therefore do so inaccurately. ; - )
Jeremy Reimer published historical computer ...
- 7,208
31
votes
Algorithm for Apple IIe and Apple IIgs boot/start beep
What is algorithms use for boot/start sound (when turn on computer)
Algorithm? Well, yes, technically everything is an algorithm. In this case it's simply executing the beep subroutine during reset, ...
- 207k
30
votes
Accepted
Why did the original Apple //e have two sets of inverse video characters?
Why did the original Apple //e have two sets of inverse uppercase characters?
Simple: To allow lower case inverse letters.
It's all about the clever way Woz arranged the original II's single ...
- 207k
29
votes
Accepted
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 ...
- 24.5k
27
votes
Is it possible to swap the Apple IIc's monochrome CRT tube for a color one?
If you don't know, then the answer is "no".
It certainly is possible to get a color CRT tube and matching electronics and fit them into a cleared out case.
However, if you have to ask people on the ...
- 295
27
votes
Accepted
What exactly were those large orange chips on the Hayes Micromodem II interface card?
The 207C300 and 207C400 are "active filters for use with modems." They were manufactured by Sprague.
I found an advertisement for them in Electronic Design magazine, volume 26, number 4, ...
- 2,666
26
votes
Accepted
Why was it possible to cause an Apple //e to shut down with SHIFT and paddle button 2?
The keyboard on the Apple II+ was designed to type uppercase letters only, which rather limited the machine's usefulness for word processing. Because almost nothing used paddle button 2 and very few ...
- 33.9k
26
votes
Accepted
What is DRAM refresh and why is the weird Apple II video memory layout affected by it?
Summary
Each DRAM chip has multiple "rows" of memory, and each row needs to be
accessed in a certain way (not necessarily via a read or write) on a
regular basis in order to avoid the memory ...
- 24.5k
25
votes
Accepted
How can I programmatically tell which version of Apple II my code is on?
The way to identify different Apple IIs is described in Apple II Miscellaneous Tech Note #7. Excerpting from that document:
To identify which computer of the Apple II family is executing your ...
- 8,605
25
votes
Accepted
Why is the Apple II hi-res HGR command so slow?
If you look at the screen clear code in the Applesoft BASIC ROM, you'll find this:
f3f6 lda $e6 ;put base address of current hi-res page
sta $1b ; into $1a/1b (will be $2000 ...
- 8,605
25
votes
Accepted
What are the "Screen Holes" in Apple II graphics?
1. What are screen holes?
The Apple II video architecture is based around a text display of 40 columns by 24 rows. Woz had already built an ARPANET terminal for a TV, and said in his book iWoz that "...
- 7,208
25
votes
What was the point of Apple Pascal having its own file system?
UCSD Pascal was developed prior to the Apple II, during the 70's in San Diego, using PDP-11 class machines with a 512-byte block disk structure. In the process of porting it to microcomputers, often (...
- 207k
25
votes
What is DRAM refresh and why is the weird Apple II video memory layout affected by it?
DRAM requires that each row of the memory is read and re-written regularly, at least every few milliseconds for the devices available at the time the Apple II was designed. This contrasts with the ...
- 16.6k
25
votes
Accepted
How are the randomizer values on the Apple II maintained?
It's incremented while waiting for keyboard input.
The 16-bit random seed (RNDL and RNDH) is updated by the KEYIN routine as it spins while waiting for a key press. KEYIN is used by the Monitor ROM's ...
- 416
24
votes
Accepted
Absolute maximum number of nibbles on an Apple II floppy disk track?
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 ...
- 7,208
24
votes
Accepted
How do accelerators and CPU cards work on the Apple II?
how do CPU cards work on the Apple II if there's no way to take the bus over?
That's what /DMA (pin 22) is good for. It halts the CPU and tristates the bus. Now any card can take over.
Unlike its ...
- 207k
Only top scored, non community-wiki answers of a minimum length are eligible