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Forum: Retrogaming General Discussion 16 February 2022, 11:54
Replies: 399
Views: 74,700
Posted By chb
AFAIK the only meaningful way to use the blitter...

AFAIK the only meaningful way to use the blitter for zooming is the iterative approach - split the object in two halves, blitt them one pixel apart, fill the gap with a doubled 1-pix column/row,...
Forum: Coders. General 23 January 2022, 13:02
Replies: 9
Views: 2,391
Posted By chb
Ah, I guess you are referring to the "A500...

Ah, I guess you are referring to the "A500 Homage" 40k?
https://www.pouet.net/prod.php?which=9268

There's some amazing code in that one indeed... (and great music and a nice design).
Forum: Retrogaming General Discussion 21 December 2021, 18:20
Replies: 86
Views: 8,598
Posted By chb
AFAIK the back layer is only 2 bitplanes there (4...

AFAIK the back layer is only 2 bitplanes there (4 colors + a lot of copper usage). Maybe 6 bitplanes would have been too taxing memory bandwidth-wise.
Forum: Retrogaming General Discussion 21 December 2021, 12:19
Replies: 86
Views: 8,598
Posted By chb
The C64 version was actually reverse-engineered...

The C64 version was actually reverse-engineered and converted from the Master System's Z80 code. Sega seems to be quite relaxed about fan-made conversions without commercial intent.
Forum: Coders. Asm / Hardware 14 December 2021, 09:19
Replies: 293
Views: 271,308
Posted By chb
I've never seen a hard number what difference...

I've never seen a hard number what difference from the standard clock is possible via /XCLK, just mentions that it should be small and not exceed 1-2% (which would not suffice for teletext). Did...
Forum: support.Hardware 03 December 2021, 12:59
Replies: 30
Views: 3,011
Posted By chb
You could have a look at this project: ...

You could have a look at this project:
https://www.pcbway.com/project/shareproject/Amiga_SID_Music_Card_Zorro_II.html
Forum: Coders. General 03 December 2021, 12:34
Replies: 9
Views: 2,391
Posted By chb
Rock Lobster by Oxyron has a pretty impressive...

Rock Lobster by Oxyron has a pretty impressive dot routine and the source is on github (https://github.com/AxisOxy/Planet-Rocklobster). From the doc:

Might be worth a look.
Forum: Nostalgia & memories 22 November 2021, 10:49
Replies: 826
Views: 96,786
Posted By chb
IMHO with SHRES they just found some application...

IMHO with SHRES they just found some application for the new 35 ns modes while keeping a TV-compatible signal. Maybe it even would have been more complicated to leave it out. :) It is moderately...
Forum: Nostalgia & memories 20 November 2021, 17:14
Replies: 826
Views: 96,786
Posted By chb
That's true, but for sequential access DRAM was...

That's true, but for sequential access DRAM was faster already then. The Acorn Archimedes made extensive use of that, and earlier the Sinclair Spectrum(!) used page mode to read bitmap data and...
Forum: Nostalgia & memories 15 November 2021, 07:40
Replies: 826
Views: 96,786
Posted By chb
Yes, obviously. But as I wrote, in real life text...

Yes, obviously. But as I wrote, in real life text mostly has the same chroma value as the background (black on white, white on black, black on gray, even green or amber or whatever color on black,...
Forum: Nostalgia & memories 14 November 2021, 11:52
Replies: 826
Views: 96,786
Posted By chb
You're mixing up some things here. 422 or 420...

You're mixing up some things here. 422 or 420 color subsampling is perfect for the absolute majority of text output. Just take black on white or black on grey. Chroma subsampling is totally...
Forum: Nostalgia & memories 13 November 2021, 16:39
Replies: 826
Views: 96,786
Posted By chb
Yes, completely right. But I guess that would be...

Yes, completely right. But I guess that would be quite some effort for a limited benefit (YUV HAM mainly), and there might have been no standard ICs available for that task (the A1000 uses a standard...
Forum: Nostalgia & memories 13 November 2021, 15:33
Replies: 826
Views: 96,786
Posted By chb
It's a bit more complicated - only PAL is...

It's a bit more complicated - only PAL is (mostly) YUV, NTSC is YIQ, SECAM YDbDr. Those are very similar, but not the same, which gives another argument for RGB - no need to do region-specific...
Forum: Nostalgia & memories 13 November 2021, 06:02
Replies: 826
Views: 96,786
Posted By chb
Color composite is extremely bandwidth limited,...

Color composite is extremely bandwidth limited, esp. for NTSC - there's just 2-2.5 MHz for the Y signal, even a horizontal resolution of 160 pixels looks blurry. That was acceptable for a home...
Forum: Nostalgia & memories 15 October 2021, 19:17
Replies: 826
Views: 96,786
Posted By chb
But a user cannot get into the OS without having...

But a user cannot get into the OS without having a prepared disk. So without that, you can't even list disk contents or format an empty disk. It is IMHO an oversight not to have a minimal, user...
Forum: Nostalgia & memories 10 August 2021, 13:57
Replies: 82
Views: 34,615
Posted By chb
Hmm, yep, that Paul from Paul & Mandy indeed...

Hmm, yep, that Paul from Paul & Mandy indeed doesn't look totally different to this one:
http://amp.dascene.net/detail.php?view=5673&detail=photos

Interesting find.
Forum: Nostalgia & memories 18 July 2021, 23:21
Replies: 826
Views: 96,786
Posted By chb
No, most C64s won't show weird colours, as a) the...

No, most C64s won't show weird colours, as a) the pixel clock is deliberately choosen not to be in sync with the color clock, and b) the VIC II is generating separate chroma and luma signals, that...
Forum: Nostalgia & memories 16 July 2021, 16:05
Replies: 826
Views: 96,786
Posted By chb
It's a bit of a hyberbole that the C64's...

It's a bit of a hyberbole that the C64's competitors had selectable palettes before; afaik the only one were the Atari 8-bitters. Sinclair Spectrum, TI 99, Apple II, IBM CGA and a bunch of others had...
Forum: request.Music 21 May 2021, 21:11
Replies: 28
Views: 14,106
Posted By chb
One of the authors (Carsten Herbst) is on youtube...

One of the authors (Carsten Herbst) is on youtube and has commented on a SonicArranger video recently, so he could be able and willing to help you:
https://www.youtube.com/watch?v=05zPq-UvoUU
Forum: Coders. Asm / Hardware 20 May 2021, 12:34
Replies: 32
Views: 4,530
Posted By chb
AFAIK it's a variety of the "shear & zoom"...

AFAIK it's a variety of the "shear & zoom" rotator without a need for c2p. You can perform a rotation of up to 45° as a shear in x and y and a downscale. Now the x-shear is trivial on the Amiga with...
Forum: Coders. Asm / Hardware 28 April 2021, 20:41
Replies: 8
Views: 1,481
Posted By chb
AFAIK it's something like this, the programmer...

AFAIK it's something like this, the programmer wrote an article* about that technique in a German Amiga mag ('Amiga Magazin' IIRC).
It was definitely blitter-fill based, without c2p, but I do not...
Forum: Amiga scene 28 April 2021, 11:35
Replies: 1,319
Views: 280,347
Posted By chb
Just my guess: KK is saving one of three passes...

Just my guess: KK is saving one of three passes in the blitter c2p (the first one probably, as it replaces the bytes in a word) by writing the data in scrambled order; if you do it in a clever way,...
Forum: Amiga scene 06 April 2021, 10:18
Replies: 29
Views: 3,893
Posted By chb
AFAIK it was an 8 pixel buffer for...

AFAIK it was an 8 pixel buffer for c2p-conversion. The data sent from the Amiga was always chunky (so 1 pixel = 1 byte in memory), but depending on the screen mode the pixel order was not linear but...
Forum: Amiga scene 17 March 2021, 14:28
Replies: 542
Views: 57,529
Posted By chb
Only the Prowrite one seems to be in that...

Only the Prowrite one seems to be in that resolution, the spreadsheets are normal HiRes (look at the pixel size), just doubled in y for viewing in the browser.
Forum: Amiga scene 28 February 2021, 12:54
Replies: 542
Views: 57,529
Posted By chb
@Frogs: I think there's a slight misunderstanding...

@Frogs: I think there's a slight misunderstanding what the term "textmode" stands for. It just means that the screen content is represented in video ram as characters and not as individual pixels. It...
Forum: Coders. Asm / Hardware 21 February 2021, 22:58
Replies: 1,119
Views: 86,533
Posted By chb
True. IMHO also an example that it's often not...

True. IMHO also an example that it's often not the best technology that wins in the end.

Sageandstride.org (http://www.sageandstride.org/) has quite some information about both Sage and Stride...
Forum: Coders. Asm / Hardware 14 February 2021, 22:44
Replies: 1,119
Views: 86,533
Posted By chb
That's quite some nonsense. A 12 Mhz 68000 system...

That's quite some nonsense. A 12 Mhz 68000 system could be bought in 1984 for less than $3500 from Stride Micro* (400 Series...
Forum: Amiga scene 12 February 2021, 19:14
Replies: 130
Views: 14,407
Posted By chb
One could store the first frame of every move...

One could store the first frame of every move uncompressed to hide that latency (the animation speed is probably way less than 50 fps, more like every 3rd frame or so).
Forum: Coders. Asm / Hardware 11 February 2021, 13:13
Replies: 298
Views: 26,081
Posted By chb
I think buggs reported something similar here...

I think buggs reported something similar here (http://eab.abime.net/showpost.php?p=1453758&postcount=73):

It is a bit funny, because I have seen that 56 kHz figure for AGA/ECS countless times, but...
Forum: Retrogaming General Discussion 30 January 2021, 12:45
Replies: 264
Views: 27,908
Posted By chb
I think I understood the question wrong - I...

I think I understood the question wrong - I thought it was about shires sprites, but it wasn't. Thanks for pointing that out.

BTW, you were at some point investigating the possibility to...
Forum: Retrogaming General Discussion 30 January 2021, 09:53
Replies: 264
Views: 27,908
Posted By chb
No, the DMA slots for sprites are fixed, and they...

No, the DMA slots for sprites are fixed, and they always load the same amount of data to the sprite registers for all sprite and display resolutions - just depending on the sprite width/fetchmode.
Forum: Coders. Asm / Hardware 23 January 2021, 19:59
Replies: 1,119
Views: 86,533
Posted By chb
Which operating systems that ran on the 8086 made...

Which operating systems that ran on the 8086 made use of fork()? Which operating systems that ran on the 8086 used relocation?

BTW, it's rather trivial on the 68000 to write relocatable code if...
Forum: Retrogaming General Discussion 21 January 2021, 18:58
Replies: 57
Views: 4,992
Posted By chb
AFAIK it was moderately successful in Europe in...

AFAIK it was moderately successful in Europe in that role, especially in Germany. Calamus (DTP) was very popular for some time, also some CAD applications do exist. And it was quite popular as a word...
Forum: Retrogaming General Discussion 21 January 2021, 13:49
Replies: 57
Views: 4,992
Posted By chb
CGA has exactly the horizontal refresh rate as an...

CGA has exactly the horizontal refresh rate as an OCS Amiga - 15.6 kHz. CGA hires hence is identical to Amiga hires in resolution and refresh rate (actually the Amiga can show a bit more pixels...
Forum: Coders. Asm / Hardware 14 January 2021, 17:58
Replies: 234
Views: 24,797
Posted By chb
AFAIK it is No. 2 - when choosing AM or FM, the...

AFAIK it is No. 2 - when choosing AM or FM, the word-sized valued fetched by DMA are just written to the volume or period register:
Forum: Coders. Asm / Hardware 14 January 2021, 13:39
Replies: 234
Views: 24,797
Posted By chb
From what I got from Henryk's paper, Paula works...

From what I got from Henryk's paper, Paula works at a base frequency of ~3.58 MHz, and PWM is using 64 cycles. So when setting a replay period of 64 (equaling a sample replay frequency of 3.58 Mhz/64...
Forum: Coders. Asm / Hardware 14 January 2021, 12:15
Replies: 234
Views: 24,797
Posted By chb
Thank you for this extremely interesting and...

Thank you for this extremely interesting and comprehensive paper! It never occurred to me that the mismatch between the sampling frequency and the PWM-period introduces noise.

Do you have an...
Forum: Coders. Asm / Hardware 13 January 2021, 12:20
Replies: 234
Views: 24,797
Posted By chb
Same for me, I mainly hear a different frequency...

Same for me, I mainly hear a different frequency response. The A600 sounds quite muffled.
While in theory the A600 and the A1200 should have the same fixed filter, it seems like that's not always...
Forum: Coders. Asm / Hardware 12 January 2021, 17:27
Replies: 234
Views: 24,797
Posted By chb
There's a very comprehensive document...

There's a very comprehensive document (http://bax.comlab.uni-rostock.de/dl/Paula_SystemTheoretic.pdf) by Henryk Richter on Amiga audio and also on calibration (section 4.2). He also discusses...
Forum: Coders. Asm / Hardware 12 January 2021, 16:07
Replies: 234
Views: 24,797
Posted By chb
There's most likely no voltage DAC for the...

There's most likely no voltage DAC for the volume, but PWM volume control - there shouldn't be linearity issues with that.

BTW, interesting experiment.

EDIT:

I think that is a debatable...
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