Scali

6 ms·

1.
by Scali 3y ago
On a PC it is different, because you need to render the polygons in software. On an Amiga you basically draw lines into each bitplane, and then do a single area fill at the end, all with the blitter. The area fill won't have to be stor
2.
by Scali 3y ago
That is an interesting difference with the 8088+CGA platform by the way. The Amiga has no problem displaying entire screens of uncompressed data. CGA however is so bandwidth-limited that you simply can't update an entire screen at ac
3.
by Scali 3y ago
Well, I would argue that a 'conventional' video codec would not work nearly as well on a stock Amiga 500 as this polygon approach does. The closest thing to full-motion video on the platform was probably what they used on the CDTV
4.
by Scali 3y ago
The Amiga had a hardware blitter that was very good at drawing lines and doing area fills, so it made perfect sense to encode video to polygons on that particular hardware.
5.
by Scali 3y ago
It was actually patented by Access Software, under the name of RealSound. https://en.wikipedia.org/wiki/RealSound
6.
by Scali 3y ago
Having said that, the CGA card does not actually have its own clock. It takes the NTSC base frequency of 14.31818 MHz from the OSC-pin of the ISA bus. On early PCs, such as the IBM 5150/5160, the CPU frequency is also derived from this
7.
by Scali 3y ago
Yes, thanks! Fixed the original text.
8.
by Scali 3y ago
Yes, combined with streaming the data from disk in realtime, and playing the audio over the PC speaker in this case, bit-banged. Given the limited performance of both the HDD system and the CGA adapter, the most important thing the compiler
9.
by Scali 3y ago
The video clock (I assume you mean pixel clock) isn't relevant. The synchronization of video and audio happens on a per-frame basis. And since the frames are clocked out on the audio-clock, there cannot be any drift.
10.
by Scali 3y ago
Yes, I posted a followup which investigates the issue somewhat further. It appears to be some bug with the message queue handling, specifically when the UI is in Aero mode. In classic mode, the problem is not there. In Windows XP, the probl
11.
by Scali 3y ago
Exactly. As I tried to explain, you NEED a context switch (which doesn't make it a spin-wait) in order to avoid the deadlock between your main loop and the processing of the Windows message queue (and as you see, I do check the quant
12.
by Scali 4y ago
Some will agree, some won't. This is a good watershed moment to cut off the ones that won't.
13.
by Scali 4y ago
"Justify why people died" Lol, you sound as unhinged and radicalized as Jim. The point I was making was that all these people had a criminal record that showed they had a violent nature, and were likely there to cause trouble. But
14.
by Scali 4y ago
The ATi Small Wonder is not entirely cycle-accurate. When I studied the CGADEMO by Codeblasters, I found that the scroller didn't look entirely correct, because the Small Wonder was slightly slower: https://scalibq.wordpress
15.
by Scali 4y ago
Given that the demo targets AT-class hardware, it is unlikely that something like PCem or MESS was used, because in those cases you'd actually have to select an AT-configuration to make it work, instead of an XT-configuration. DOSBox d
16.
by Scali 4y ago
I wonder... certain software, such as Flight Simulator and Lotus 1-2-3 had a profound effect on the level of compatibility of clones. So perhaps if software was released that demanded EVEN MORE compatibility, we would have even more compati
17.
by Scali 4y ago
That is known to happen, yes: https://scalibq.wordpress.com/2015/08/09/fixing-genesis-proj...
18.
by Scali 4y ago
What may also have had an impact was that clones were generally XT-clones (using the newer, smaller ISA card layout, and no cassette port), not PC-clones. And indeed, they were specifically advertised as 'XT-clone', 'XT-class
19.
by Scali 4y ago
Yes, especially somewhat later in the life of the 8088, most applications would demand quite a bit of memory, and the 640k configuration became standard for the later 5160s and most clones. So I wouldn't be surprised if 5150 owners als
20.
by Scali 4y ago
I wouldn't know if 'most of them' don't work, but I know for a fact that I have one (made by Vivanco, using a Prolific chip) that works fine in combination with my IBM 5160. I use it in combination with FastLynx, which s
21.
by Scali 4y ago
Not on the original PC/XT machines, as the ISA bus was basically the CPU data bus. So regardless of whether you had memory on board or on an ISA card, data transfers were exactly the same speed. On later machines, the CPU would be cloc
22.
by Scali 4y ago
In short, textmode gives you 80x25 characters of 8x8 pixel resolution each, making 640x200 resolution, with 16-colours, where each character can be assigned a foreground and background colour. The 'Macrocom Method' reprograms the
23.
by Scali 4y ago
Correct, as "XT" stands for eXtended Technology. You can't extend it without having the basic technology first. The 5150, aka the PC, was that basic technology. However, in terms of CPU, graphics, sound and all other aspects
24.
by Scali 4y ago
That was how the predecessor 8088 MPH worked. Area 5150 however is aimed at a TTL RGBI monitor, and as such, does not use NTSC composite artifacting. It can only display 16 colours at once. So in this demo, you get 640x200 in 16 colours, wh
25.
by Scali 4y ago
Yes, originally CGA and MDA at the same time. Hercules was a non-IBM standard, based on MDA. Hercules has 64k of memory, where 32k is in the area of MDA, and the second 32k overlaps with the CGA area. You could disable the second 32k when y
26.
by Scali 4y ago
This was in the context of using the video as a texture. As I tried to explain, the RGB texture formats with 8-bit precision use 32-bit words. There are no 24-bit formats available as a texture format. NV12 is also a native texture format,
27.
by Scali 7y ago
I would like to nuance that by saying it's nice if you have a good deal of domain knowledge, but my article focuses more on the case where you venture into new territory, and the architect is the person who needs to obtain the required
28.
by Scali 8y ago
In theory emulators recreate the hardware in software. In practice, emulators approximate the hardware in software. In the case of PCs, there is so much hardware variation, that it was never a requirement to be very accurate in terms of s
29.
by Scali 11y ago
The artifact colours are quite off as well, so I suspect the card used was not a real IBM CGA card. On my ATi Small Wonder and Paradise PVC4 cards, I get the exact same Kefrens bars, with the top chopped off. Having said that, the fact that
30.
by Scali 11y ago
Yes, CGA has an RCA connector on the back for NTSC composite. This is what we used for the demo. There is also a header on the card itself, to which an RF modulator can be connected, for a regular TV antenna input (this was an option, proba

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