32 votes
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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 ...
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32 votes
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Reason for popularity of Apple IIGS

For one, the II GS was the newer machine - providing a colour desktop and ADB before any Mac. From a user perspective GS/OS offered everything the Mac did. Plus compatibility with an uncountable ...
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  • 173k
19 votes
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How did Apple's 'CYA' chip function to "Control Your Apple"?

The "Control Your Apple ASIC" (CYA) was part of the "Apple IIGS 1 MB" introduced in 1989, which had 1.125 MB of DRAM and twice the ROM space of previous IIGS models. The CYA was much the same as the "...
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  • 400
17 votes
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Apple IIgs: Hardware implementation of RAM shadowing

That's an interesting and especially well prepared question. Thank you. AFAIR your second assumption is right. When shadowing is enabled for a region (see below) the CPU gets synchronized and slowed ...
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  • 173k
16 votes
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How did the Apple IIGS automatically slow 5.25 inch disk I/O code for backwards compatability?

From the Apple IIgs Hardware Reference, Second Edition, pages 22-24: Figure 2-6 - Speed register at SC036 Table 2-2 - Bits set in the Speed register [...] Bits 0-3† Value 1 Description Disk II motor-...
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14 votes
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Apple II GS versus Mac Plus cost

The Macintosh sold for more because — as the shiny new thing — it could be sold for more. It was marketed as an aspirational product, not sold as a reasonable markup on an engineering BOM. The IIgs ...
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  • 17.2k
13 votes
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What FSTs (File System Translators) exist for the Apple IIGS?

The official ones, with GS/OS versions as indicated by the Apple II History site: Filename Purpose In GS/OS Version APPLESHARE.FST For AppleTalk networks ...
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13 votes

How do I use shadowed memory to render Super Hi-Res quickly?

The memory shadowing feature copies writes from $01/2000-9FFF to the corresponding location in bank $E1. What you want to do looks like this: Perform computation for the current frame. Disable ...
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  • 7,591
12 votes
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Help identify old Apple game from 80s (Apple II, Apple IIGS)

Sounds quite like Tass Times in Tonetown. Although, IIRC it was about saving Grampa and the antagonist was a kind of a croc with several other besats mixed in 'man', but otherwise it fits. And yes, ...
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  • 173k
12 votes
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What is the maximum amount of memory that can be added to an Apple IIGS?

The largest amount of RAM supported by a real Apple IIgs is an 8MB expansion card, but that's somewhat misleading. The original IIgs came with 256KiB and the ROM3 came with 1MiB. A RAM expansion of ...
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  • 1,029
12 votes
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Inserting NOPs to improve IIgs shadow copy performance

Mythbusted! With 2021 knowledge of how the FPI/CYA work, this simply didn't make sense. So I plugged in a logic analyser and timed the Wolfenstein 3D code (NOP every 8 PEI's). I then modified the code ...
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12 votes

Inserting NOPs to improve IIgs shadow copy performance

Keep in mind that because the memory in banks $E0 and $E1 are used as the 128K of memory in 8-bit mode (yeah, it's counterintuitive), they are controlled by the MEGA II chip, which is in essence an ...
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11 votes
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How many cards can safely be put in a IIgs?

In general, the IIgs was designed to have a full house in regards to expansion cards, just like every other member of the expansion slot Apple II family. There are guidelines for how much power a card ...
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  • 14.3k
11 votes

How do I interpret the old Mac character set?

The character set is known as "Mac OS Roman". The official mapping from Mac OS Roman to Unicode can be found on unicode.org. While the character set is similar to Windows-1252 and ISO-8859-1, having ...
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  • 7,591
10 votes

How do I interpret the old Mac character set?

From a more practical point of view, the program to convert between different character sets is called iconv. It can be used on the command line from the OS X (Mac) terminal, as well as in most Linux ...
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  • 602
10 votes
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How can I tell if an Apple II disk image is bootable?

The bootprocess itself don't know any 'not bootable' exit. If a disk can be read, the first sector is loaded at 800 and then jumped to 801 (800 holds a counter for the number of sectors to read by the ...
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  • 173k
10 votes
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Why wasn't the Z6 version of the Infocom Z-machine ported to the IIgs?

I suspect it was too late in the game for Infocom... The Apple II port of YZIP, Infocom’s Z6 interpreter, was released in 1989 (as far as I can determine), and by then Infocom was only a publishing ...
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9 votes
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What is stored in IIgs BRAM?

What is stored in the IIgs PRAM? Basicly everything you can set via the Control Panel I'm going to replace my PRAM battery in a ROM 03 IIgs and that got me thinking about what is stored in PRAM. I ...
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  • 173k
9 votes
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How does Apple ][gs hardware dithering work?

The Apple IIgs Hardware reference explains it: In 640-pixel mode, color selection is more complicated. The 640 pixels in each horizontal line occupy 160 adjacent bytes of memory, each byte ...
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9 votes

Reason for popularity of Apple IIGS

Your question conflates two questions into one: Did the IIgs sell more than the Mac in 1986? If so, why did the IIgs sell more than the Mac? Others have given valid reasons for (2), but there is ...
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8 votes

Checklist for powering up an Apple IIgs?

Generic answer, applies to any machine of a similar design in that condition: If you can, check the power supplies (not just for the machine preferably, on anything you are attempting to connect to ...
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8 votes

How did the Apple IIGS automatically slow 5.25 inch disk I/O code for backwards compatability?

In reference to the comment "Any idea how the IIGS implements those Disk II motor detectors?" There's this Technical Note #68: Tips for I/O Expansion Slot Card Design. It says: On the Apple ...
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7 votes

What is the maximum amount of memory that can be added to an Apple IIGS?

According to the Apple IIgs Hardware Reference, Second Edition, page 49: The original Apple IIgs has 256K of RAM and 128K of ROM built in, and the 1 MB Apple IIgs has 1 MB RAM and 256K of ROM. ...
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  • 7,591
7 votes

What is the maximum amount of memory that can be added to an Apple IIGS?

The CPU in the IIgs can address up to 16 megabytes of memory. Due to lack of address lines on the CPU chip, the upper 8 bits is sent out on the data bus before each memory access and is latched by ...
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6 votes

How to print from a IIgs to a modern printer?

I don't know if I can say this for 100% certainty for every HP printer ever, but in general Hewlett Packard printers that support HP's own Page Control Language (PCL), which as far as I know is every ...
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  • 3,491
5 votes
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AppleTalk adapters to bridge LocalTalk to Ethernet?

What you need is a LocalTalk to Ethernet bridge. It's possible to use a computer for this but in general the most reliable and easiest path is to use a device made for this purpose. For example, I ...
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  • 11.3k
5 votes
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Could the Apple IIGS play any and all Amiga MOD files?

There are many routine features of a MOD that do not map directly to the IIGS sound hardware — besides the 64kb limit, the Ensoniq also requires samples to be a power-of-two in size and will loop ...
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  • 32.5k
4 votes

Reason for popularity of Apple IIGS

There was a big "Apple II Forever" push encouraging users to upgrade. Also schools likely bought IIgses in bulk for their computer labs, driving up the sales figures.
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4 votes

Checklist for powering up an Apple IIgs?

This might sound harsch to some people over protective of their little C64, but best practice is just doing - it with apropriate caution ofc. Always check the inside for obvious dirt, dust, rust and ...
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