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65

The architecture of most "color computers" of the 70s-80s was very tightly built around the NTSC color video standard. Almost all of them had a 14.31818 MHz crystal. Note that this is four times the 3.579545 MHz frequency of the NTSC color standard, which was called a "color clock". They divided that crystal frequency to derive their actual clock ...


38

The ones you list are all S.A.M, from what is now SoftVoice Inc. It was developed first for the Apple II, Lisa, Atari 8-bit machines and the Commodore 64; based on awareness of those versions, the company was contracted directly to supply the bundled speech generators for the Macintosh and Amiga. So they all sound the same because they are ports of the same ...


37

The differences between PC floppy drives and Amiga floppy drives are as follows: PC floppy drives normally answer to drive select 1 (DS1), internal Amiga drives answer to DS0 pin 34 on the connector is used for disk change on the PC, disk ready on the Amiga pin 2 on the connector is used for high-density detection on the PC, disk change on the Amiga So ...


34

Any accelerator for the Amiga work by disabling the CPU and taking over the complete bus system to become the bus master. To accomplish this, a low level signal must be applied by the accelerator to pin BR (Bus Request). The CPU will answer asserting pin BG (Bus Grant). After the accelerator receives this signal, it acknoledges it by asserting BGACK. When ...


32

You should be able to use the Amiga hard drive directly on your Linux computer (provided it still has IDE support). Linux also understands AFFS (Amiga Fast File systems), at least once AFFS support is compiled into the kernel (from your "self customized" wording I would assume you know how to do that). Apparently, some Linux tools don't seem to understand ...


30

Memory protection. It's not that preemptive multi-tasking is expensive, or hard. It's not. It's easy. It costs (or can cost) essentially the same as cooperative multitasking. You have to save process state in both cases. But what was holding back the older systems was their early reliance on systems without inherent memory protection, and those legacies ...


29

It was an advantage because the IBM PC became an extensible computing platform. The most popular competitor to it previously was the Apple II, another open platform. The PC, as a platform, was popular to users because of the choices it enabled, as developers because of the foundations that it laid, and engineering firms because they could focus on what they ...


28

What's lacking is mostly raw number-crunching ability. The MP3 format is relatively lightweight, and can be implemented using only fixed-point math (no FPU required), but it still takes a fair amount of computation to turn compressed frequency-domain data into uncompressed time-domain data that can be fed to a DAC. This IEEE article quotes a minimum ...


28

There are a few reasons why multi-platform 3D games turned out to be no faster on the Amiga than on other 68000-based platforms without its blitter: The developers may have targetted the lowest common denominator system and not taken advantage of the blitter when they ported to the Amiga. Early games and poor conversions tended to be like this. A naive ...


27

The first change is to patch this code: 00fc0196 266E003E movea.l $3e(a6), a3 00fc019a B7FC00080000 cmpa.l #$80000, a3 00fc01a0 622C bhi.s $fc01ce.l 00fc01a2 B7FC00040000 cmpa.l #$40000, a3 00fc01a8 6524 bcs....


25

As far as I know, there's no authoritative source, and the information out there is probably not really accurate. I will answer this from an electrical engineering perspective, and because I have implemented some of these fixes myself. First a little note about timing fixes: The expression timing fixes is not really accurate, but comes from the observation ...


25

After some research, I found the hardware engineer that built the DCTV and we exchanged some messages where he explained the system. This is the unedited text: Wow, it has been a long time... I didn't really remember! Luckily I still have all the lab books and design notes from those days filed away. We used a technique that encoded the data on two ...


24

If you include clones, home retro computers were sold far into the 90's, including the Milan (Atari ST compatible, 1997-1999) and various Amiga compatible machines. There were also lots of ZX Spectrum clones produced in East Europe until the late 90's. However, if it's just about systems supported by their original manufacturer, the answer is likely: Acorn. ...


23

EHB For example, a game that uses EHB (Extra HalfBrite) mode during the game action (i. e. ingame) is Pinball Dreams. In my example run of the Beat Box table I can find the following in the copper list: $00D6EA WAIT $4211FFFE $00D6EE MOVE #$6200,BPLCON0 I. e. it waits for raster line $42 (66) and uses BPLCON0 to set the number of bitplanes to 6 without ...


23

That expansion port exposes all the signals from the 68000 CPU, plus some other Amiga specific signals, such as the color CLK, ROM and RAM select signals, along with voltage supply lines, etc. It is documented in the schematic, page F-9 of the User's Manual. It worked by removing its trap door, and plugging in a compatible device with the Amiga switched off....


23

Ranger was to be the next generation Amiga, which the original West Coast Amiga engineers began working on in 1986-87, following the release of the Amiga 1000. Jay Miner improved the graphics chipset for Ranger to address the twin problems of chip (i.e. Graphics, Sound, DMA) RAM memory space and bandwidth in the Amiga 1000. The Original Amiga chipset (OCS) ...


21

MOD is the file extension for SoundTracker modules. SoundTracker and its successors (NoiseTracker and ProTracker predominantly, although there are other derivatives) are sequencers, and load and save files in this format. It was originally designed for games and demo programmers - assembly code to play back the modules was commonly available and worked ...


21

Right off the top, SIMM type modules have higher pin densities and are mechanically far more robust than that ZIP chip package. It'd be relatively easy to bend pins getting these things in an out (possibly worse than DIPs even), and protecting the pins in transport looks even harder than doing so with DIP chips. Remember that many retailers are unlikely to ...


20

As the sound channels had independent linear 64-step volume control (6 bits + mute setting), by calibration and splitting sample bits for one 14bit waveform across two channels, two-channel 14bit (stereo) sound could in principle be improvised using all 4 channels. This would be done by playing A coarse part of the waveform generated from the higher 8 bits ...


20

The Amiga disk format stores 512 bytes per sector, 11 sectors per track (a track is one side of a cylinder), double sided (i. e. 2 tracks per cylinder) with 80 cylinders per disk, which makes 80 * 2 * 11 * 512 = 901120 bytes = 901.12 kB = 880 KiB raw block data. The IBM-PC format also stores 512 bytes per sector, but only 9 sectors per track (on a Double ...


20

All of the 68k-based computers (Amiga, Atari ST and Sinclair QL, as well as the classic Macintosh) went to market in a rush. And all of them went to market before the OS (and, thus, the ROMs) were really "finished". The QL initially had an outboard ROM extension that later on had to be replaced with the "final" ROMs (so, the computer had to be sent back to ...


20

Even though with a standard floppy drive there is no way to read it, there are several ways to do this: If you have two floppy drives, you can use a program called Adfread (download) to override the way Windows reads the second. This only works with Windows 2000 onwards, (but not Windows ME). The SuperCard Pro or Kyroflux controllers, that can be connected ...


20

When color video was introduced in the USA, the horizontal scan rate was set as precisely 15750 * (1000/1001)Hz, i.e. roughly 3579545.4545Hz and the color sub-carrier frequency (also called the chroma clock) was defined as 227.5 times the horizontal scan rate. Many computers of that era use a multiple of the chroma clock as the pixel clock (the Amiga, for ...


19

On a PAL Amiga, a full line sweep translates to about 454 virtual Lores (Low Resolution) pixels. (64 µs duration of a horizontal line, 7.093790 MHz pixel clock =~ 140.968 ns per pixel: 64 µs / 140.968 ns =~ 454). I say virtual pixels because not all of those pixels are actually usable as there is the horizontal sync period of about 4 µs and the back porch ...


19

First of all you should remove all unnecessary peripherals and cables from the Amiga, in case it is a faulty device that is preventing it from working. All you need is the power cable, display cable, and maybe a mouse. If the Amiga works in this state, then the fault is most likely to be one of the peripherals. But if it still doesn't work, then read on. ...


19

The question should rather be: "What could it have been?" - It never made it into an existing machine. According to some Internet lore, Kelly would have been the A3000+'s/AA3000's RAMDAC (digital video memory to analog RGB converter chip) that Commodore was initially planning to develop themselves. According to the same lore, during the development of ...


19

Speaking for the Macintosh here. TL;DR: It wasn't possible to do this in a compatible manner after the hardware was capable enough. Compatible to the already existing application base. You'll need to see this in context with the heritage of the Macintosh Operating System itself. It was built to run in an considerably limited environment, regarding CPU ...


19

The [pre-AGA] Amiga: uses a planar frame buffer, stored in memory that is shared with the CPU (and which therefore reduces the CPU's speed); provides dual-playfield hardware scrolling, but the total bit fetch total per output byte doesn't stretch beyond six, so you end up with e.g. a 7 colour foreground and an eight colour background; provides 8 hardware ...


18

The sound came from the fact that drives would only report on the presence of a disk if the heads were moved. Thus by default, the OS would move the heads back and forth. Alternatively, the heads could be moved fully to one side and then asked to step further to that side (by default the heads would be centered to minimise seek time or read the central ...


18

One could just as easily ask why it was not extended to 64 bits, or even wider. Well, if you ignore backwards-compatibility and cost, yes, it could have been. I'll pretend we can ignore backwards-compatibility and concentrate on cost first. Making the data pathways 32 bit would immediately double the number of transistors, with a corresponding doubling of ...


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