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Forum: Amiga scene 06 April 2021, 10:18
Replies: 29
Views: 2,200
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: 476
Views: 29,740
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: 476
Views: 29,740
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: 68,827
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: 68,827
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: 124
Views: 10,312
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: 13,875
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: 21,832
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: 21,832
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: 68,827
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: 3,656
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: 3,656
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: 15,496
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: 15,496
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: 15,496
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: 15,496
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: 15,496
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: 15,496
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...
Forum: Coders. Asm / Hardware 12 January 2021, 15:47
Replies: 234
Views: 15,496
Posted By chb
I do not think that pre-emphasis would have any...

I do not think that pre-emphasis would have any effect on a 441 Hz signal, as it is well below the LPF frequency. But his improved calibration may.
Forum: Coders. Asm / Hardware 12 January 2021, 12:34
Replies: 234
Views: 15,496
Posted By chb
Easiest way: Put a 16 bit sample in a sample...

Easiest way: Put a 16 bit sample in a sample editor, reduce the volume in the editor to 25% (so it uses only a 14 bit range), and play it back, restoring the volume level using your amplifier or your...
Forum: Coders. Asm / Hardware 12 January 2021, 12:21
Replies: 234
Views: 15,496
Posted By chb
AFAIK the second channel is playing at volume 1...

AFAIK the second channel is playing at volume 1 and uses only the lower 6 bits, so at least in theory there shouldn't be any steps of voice 2 fitting into the voice 1 steps, just non-overlapping...
Forum: Amiga scene 09 January 2021, 11:13
Replies: 139
Views: 17,902
Posted By chb
Four channels is slightly inconvenient for music...

Four channels is slightly inconvenient for music + SFX, because for a line-up very common in pop/rock music you'd need at least drums, bass, chords and melody. On the other hand, four voices were...
Forum: Amiga scene 08 January 2021, 21:49
Replies: 139
Views: 17,902
Posted By chb
I think having 8-16 lines or about 4kB of buffers...

I think having 8-16 lines or about 4kB of buffers in Paula would be absolutely outside the possibilities of the time. That's about 200k transistors just for the buffers. An additional bus for Paula...
Forum: Retrogaming General Discussion 18 December 2020, 13:16
Replies: 392
Views: 39,434
Posted By chb
I could see a benefit for a scene with lots of...

I could see a benefit for a scene with lots of smaller polygons, those are quite inconvenient in planar modes - e.g. a 10 pix wide polygon needs 16-32 memory accesses per horizontal span in 8 bit...
Forum: Amiga scene 18 December 2020, 12:11
Replies: 590
Views: 38,976
Posted By chb
Just for the sake of completeness in an honestly...

Just for the sake of completeness in an honestly quite bizarre thread: Akiko cannot use DMA for chunky-to-planar conversion. Its DMA capabilities are limited to data transfer from the CD-ROM (which...
Forum: Coders. C/C++ 02 November 2020, 14:55
Replies: 44
Views: 3,126
Posted By chb
Yep, that's exactly why I put those two versions...

Yep, that's exactly why I put those two versions there.:agree
@bebop: Try to multiply #$FFFF by #100 using only word-sized instructions...

I used those colorful and handy tables from the NeoGeo...
Forum: Coders. C/C++ 02 November 2020, 11:38
Replies: 44
Views: 3,126
Posted By chb
Yep, I guess the following is the fastest you...

Yep, I guess the following is the fastest you could do with shifts in this case:

; multiplication by #100
; x in d0, result in d1
lsl.l #2,d0 ;12
move.l d0,d1 ;+4
lsl.l #3,d0 ...
Forum: Coders. C/C++ 01 November 2020, 15:41
Replies: 10
Views: 1,005
Posted By chb
Yes, correct IMHO. No, because the...

Yes, correct IMHO.


No, because the number of instructions fetched is lower, as EB wrote. To write out two words from a register (a typical solid polygon span filler), the following
move.l...
Forum: Coders. C/C++ 30 October 2020, 15:27
Replies: 44
Views: 3,126
Posted By chb
I'd even just lavishly spend those 320 or 640...

I'd even just lavishly spend those 320 or 640 words on a complete table for every x value, if x_max is know beforehand. :)


As the table index is *2, it could overflow if the compiler used word...
Forum: Coders. C/C++ 30 October 2020, 13:54
Replies: 44
Views: 3,126
Posted By chb
On 68000/10 you also could substitute the...

On 68000/10 you also could substitute the following

UWORD m = 1 << (15 - (x & 0x000f));

by a single table lookup; but that needs additional memory (DISPLAY_WIDTH_IN_WORDS*4 bytes) and might...
Forum: Coders. C/C++ 30 October 2020, 12:52
Replies: 44
Views: 3,126
Posted By chb
Ech, of course it's 2**DISPLAY_DEPTH, not the...

Ech, of course it's 2**DISPLAY_DEPTH, not the other way round! Sorry for that.



Yes, also true. I tried to avoid an off-by-one error and introduced it. :) Should have written that that code was...
Forum: Coders. C/C++ 30 October 2020, 10:38
Replies: 44
Views: 3,126
Posted By chb
Small optimisation: Shifts are not exactly fast...

Small optimisation:
Shifts are not exactly fast on the 68000/10 (much better on the 020+), so this is a bit quicker, but maybe less readable

for (UWORD i = 1; i <= DISPLAY_DEPTH_2; i += i, p +=...
Forum: Coders. Asm / Hardware 24 October 2020, 23:12
Replies: 7
Views: 770
Posted By chb
Not tried this, but the ECS/AGA non-PAL/NTSC...

Not tried this, but the ECS/AGA non-PAL/NTSC modes are really not well documented. Probably easiest way would be a) use the OS to open the screen (probably not a viable option in your case) or b)...
Forum: Coders. Asm / Hardware 24 October 2020, 16:12
Replies: 68
Views: 3,960
Posted By chb
Yes, that's true. You'd either have the main loop...

Yes, that's true. You'd either have the main loop set up accordingly (first do a number of iterations of the modified loop with the branch, then without), or just reserve 1/(sample read delta low)...
Forum: Coders. Asm / Hardware 24 October 2020, 12:48
Replies: 68
Views: 3,960
Posted By chb
I was rather thinking of something more straight...

I was rather thinking of something more straight forward - like a simple test in the inner loop if you need to load and process a new sample or if you can continue with the old ones, but not assuming...
Forum: Coders. Asm / Hardware 24 October 2020, 11:18
Replies: 68
Views: 3,960
Posted By chb
As meynaf says, you'll have only word misaligned...

As meynaf says, you'll have only word misaligned in 25% of the cases, there's IMHO no easy way around that, at least if your sample read integer delta >1 (so you are skipping a significant proportion...
Forum: Coders. Asm / Hardware 23 October 2020, 12:09
Replies: 68
Views: 3,960
Posted By chb
Yes, but only if your longword is 32-bit aligned.

Yes, but only if your longword is 32-bit aligned.
Forum: Coders. Asm / Hardware 21 October 2020, 16:26
Replies: 68
Views: 3,960
Posted By chb
Ah, ok. AFAIK the only CPU WinUAE emulates...

Ah, ok. AFAIK the only CPU WinUAE emulates cycle-exact is the 68000; for the 68020 and upwards the emulation is less precise (because it is much harder and mostly undocumented). But I don't know if...
Forum: Coders. Asm / Hardware 21 October 2020, 15:53
Replies: 68
Views: 3,960
Posted By chb
Well, it was some nice puzzle. :) Interesting...

Well, it was some nice puzzle. :) Interesting that the table access is so slow, what was your configuration?
Forum: Coders. Asm / Hardware 21 October 2020, 14:44
Replies: 68
Views: 3,960
Posted By chb
EDIT: Did not see your last post :) Thanks...

EDIT: Did not see your last post :)

Thanks for the code, makes it clearer now.

Can a2 be saved and restored after mixing? I do not see it used anywhere in your code.

I give it a last try.:)...
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