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67

TL;DR: As explained on Steven Weyhrich's great and authoritative Apple II History Site, Wozniak simply sat down and wrote his Integer-BASIC (*1) on paper, while assembling it at the same time by hand. In his own words: I had no assembler, that was another thing. To use an assembler, they figured that somebody was going to buy this processor to use for a ...


38

One thing is certain: Steve Wozniak was very good at hand assembling 6502. Instead of writing assembler mnemonics he could simply type in the necessary hex code. I realize this isn't a proper answer but this anecdote is simply too good to relegate to a comment. It comes from Bill Atkinson remarking on Steve doing some assembler work: The other thing that ...


38

At the Homebrew Computer club in Palo Alto, California (in Silicon Valley), Steve Wozniak, a 26 year old employee of Hewlett-Packard and a long-time digital electronics hacker, had been wanting to build a computer of his own for a long time... He looked at the Intel 8080 chip (the heart of the Altair), but at $179 decided he couldn’t afford it... ...


21

Development happened very rapidly in the first two years of Apple. Wozniak did the Apple 1 in 1975 and the Apple ][ in 1976. When the Apple 1 was first presented to the world at the Homebrew Computer Club, it didn't have any name at all, since there was no company called "Apple" at the time. The original thought Woz had was simply to show off the computer he ...


20

The Card featured 256 bytes of ROM. Is there evidence documenting how the cassette program was stored? The evidence is right there in the PCB photo you added. The two MMI 6301 chips, labled APPLE A3 and APPLE A4, at position 3 and 4, are 256 by 4 PROMs. The same type, produced by Monolithic Memories, as used on the Apple 1 motherboard for the monitor ...


13

Woz was exceptional, but not the only one with this (moderate level of ?) skill in machine language. Lots of teens/kids learned to poke (from Basic) absolute hex machine code into memory on several models of personal computers (not just the Apple I/II). I knew some who could speak out-loud a small subroutine in hex for the 6502, no assembly language or ...


12

Preface: The whole circuit isn't complicated, but quite involved. I will try to use 'normal' language to make it less hard to read, as mentioning all the signals and interaction would end in an unreadable conglomeration of words. you'd write an ASCII byte to the output port and that would be displayed in the next position on the display, On the circuit ...


10

My two cents: I have written a lot of code with interrupts, and failed many times. Interrupts are very difficult to debug because they are asynchronous, you cannot easily enforce the same conditions again and again and you are fighting against race conditions and a lot of "background" operations. The main problem, in my opinion, was that Woz had to program ...


7

At that time he worked at HP, where they had of course the needed promer - the only drawback was that he had to walk to another building, as you already cited (in another question) from iWoz: I couldn’t write a new program into the PROMs. To do that, I’d have to go to that other building again, just to burn the program into the chip. I guess he did it a ...


7

The 6502 works with a single square wave clock signal that is connected to Phi0 pin 37. The chip has a built-in clock generator to use this clock input to internally generate two anti-phase non-overlapping clocks and will output these on two clock output pins, Phi1 (3) and Phi2 (39). The 6800 also needs two anti-phase non-overlapping clocks for internal ...


7

As we all know, the Apple I computer didn't last very long as it was supplanted by the hugely successful Apple II about a year later. Let's start with the fact, that it was labeled Apple 1 not I. Not only on the silk screen, but also throughout all manuals and advertisements. Similarly, the Apple II was originally named Apple 2. The II only came later, ...


7

Video output runs via a 6821 PIA and the interface exposed to the CPU is fairly simple: peripheral register B is configured so that the highest bit is an input and the low seven bits are an output. Checking its published source code, the echo character operation is in the monitor at address FFEF: ECHO BIT DSP BMI ECHO STA DSP RTS ...


5

Most CRT-based television sets sold in the US will accept any combination of horizontal sweep rate that's within a few percent of 15.75kHz and vertical sweep rate that's within a few percent of 60Hz, with any arbitrary phase relationship, even though the FCC has for many decades required that broadcast stations output signals that are within a tiny fraction ...


5

[Caveat: This question asks for opinions and guesswork] The 6800 was a well proven and widely avaible CPU, while the 6502 was brand new with an unclear future. More important, there was next to no software and no information beside the manuals available, while the 6800 already had a reasonable repository of information. As a result, it was a sensible ...


4

In this video from an auction service, the 6502 fitted is clearly shown (eg. at 2:05) as a white-ceramic packaged example with a 1576 datecode, corresponding to early April. This is before the ROR bug is certain to have been fixed, so Apple may have received a batch from near the end of the pre-fix production run. It is consistent with reliable estimates ...


3

The Apple 1 was a single design, but multiple products There were multiple incarnations of a particular computer design that would eventually be called the Apple 1: Wozniak's prototype boards. Schematic plans shared with members of the Homebrew Computer Club. Boards fabricated by members of the Homebrew Computer Club, according to Woz's schematics. Bare, ...


3

For the second part: But was there any other software sold or widely shared that deliberately worked around the ROR bug? The most prominent may be Microchess, originally developed for the KIM but ported to next to any 6502 system and many non-6502, like TRS-80 and CP/M. It might be on of only a few (the only one I know) commercially sold applications for ...


3

Original ROM The character ROM is a Signetics 2513 "64×8×5 Character Generator," a 2560-bit static ROM. (Data sheet alternate source.) Address lines A1-A3 (Signetics started the numbering at 1) select one of the eight rows of five pixels for a character (the top row is usually all-zero for a 5×7 matrix) and address lines A4-A9 indicate the ...


1

On the AppleFritter forum I happened to ask "Did the original Apple 1s built by Apple have the ROR bug?" and Cory Cohen ("Cory986") replied: Yes they did. Only the last boards out of Apple had a fixed CPU. This is one reason Mike Willegal has to make a special version of his memory test software which would run on original Apple-1 boards. I have no ...


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