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Forum: Coders. Asm / Hardware 27 August 2018, 11:15
Replies: 500
Views: 14,021
Posted By chb
Well, not really. You could a) fit several...

Well, not really. You could a) fit several sequential accesses in one slot if your mem is fast enough (like AGA's Lisa does, two 32-bit accesses) and b) it is not a strictly interleaved design, the...
Forum: Coders. Asm / Hardware 19 August 2018, 22:22
Replies: 500
Views: 14,021
Posted By chb
double post, please ignore

double post, please ignore
Forum: Coders. Asm / Hardware 19 August 2018, 22:11
Replies: 500
Views: 14,021
Posted By chb
I see the problem to get reliable benchmarks for...

I see the problem to get reliable benchmarks for such old hardware, but The ones given in the BYTE article are just nonsense for your comparision, they measure BASIC and disk/file access between...
Forum: Coders. Contest 16 August 2018, 20:33
Replies: 289
Views: 13,203
Posted By chb
If you have a lot of memory to waste, you could...

If you have a lot of memory to waste, you could also go full brute force and store 16 shifted versions of your bg image, Atari-style. :) Then all you'd need to do is setting the bitplane pointers....
Forum: Coders. General 16 August 2018, 14:25
Replies: 117
Views: 6,371
Posted By chb
No idea if it was the fastest (how would you...

No idea if it was the fastest (how would you measure that, btw?), but I do not know any game that was faster at that level of detail. It's an ST port for sure, but a) Thalion showed their competence...
Forum: Coders. General 14 August 2018, 15:24
Replies: 117
Views: 6,371
Posted By chb
Yes, sure, did I write something else? The cpu...

Yes, sure, did I write something else? The cpu can access the memory at max every 2nd memory cycle (once in 4 cpu clock cycles), 16 bit wide. But movem from register to memory is minimal 8 + 4n...
Forum: Coders. General 14 August 2018, 14:06
Replies: 117
Views: 6,371
Posted By chb
@roondar: Nice find with Alpha Waves, thanks. ...

@roondar: Nice find with Alpha Waves, thanks.

I'd also say that C just does not give you enough control for optimizing the time critical inner loops. If portability is not important for you, I'd...
Forum: Coders. General 11 August 2018, 17:32
Replies: 117
Views: 6,371
Posted By chb
Ah, interesting. As said, the fastest (and most...

Ah, interesting. As said, the fastest (and most complex and inflexible) way probably would involve writing individual code for every object shape, if you do not plan to dynamically modify them. Which...
Forum: Coders. General 10 August 2018, 12:27
Replies: 117
Views: 6,371
Posted By chb
Yep, that's what I wanted to say. As symmetries...

Yep, that's what I wanted to say. As symmetries around the origin result in same abs values for the vector elements, they are therefore beneficial for this trick. If you have other models with same...
Forum: Coders. General 10 August 2018, 10:33
Replies: 117
Views: 6,371
Posted By chb
Hmm, either I fail to make myself clear or my...

Hmm, either I fail to make myself clear or my idea is utter nonsense, both of which is totally possible :). Maybe to be clear: The idea is avoiding multiplications. If your multiplications are fast,...
Forum: Coders. General 09 August 2018, 23:57
Replies: 117
Views: 6,371
Posted By chb
My idea was mostly about reducing the number of...

My idea was mostly about reducing the number of values the coordinates can take. I was assuming you are working always with the original coordinates, or do you rotate the rotated coordinates again,...
Forum: Coders. General 09 August 2018, 22:28
Replies: 117
Views: 6,371
Posted By chb
No, that one relies on some properties of the...

No, that one relies on some properties of the binary representation of floating point numbers and makes only sense when there's a reasonably fast fpu present. On an 68000 it would be much slower...
Forum: Coders. Contest 06 August 2018, 15:40
Replies: 289
Views: 13,203
Posted By chb
If you're using 32 color bobs, it gets really...

If you're using 32 color bobs, it gets really quite tricky, and you'd need to start the blitter twice as often (unless you are not using interleaved bitplanes, but I guess you do anyhow). So quite...
Forum: Coders. Contest 06 August 2018, 13:38
Replies: 289
Views: 13,203
Posted By chb
Just a little idea: As I understand it, you're...

Just a little idea: As I understand it, you're using a 5 + 3 bitplane setup, with a palette chosen in a way that emulates dual play field mode. Then you're scrolling the 3 background planes with the...
Forum: Coders. Asm / Hardware 05 June 2018, 14:24
Replies: 31
Views: 1,862
Posted By chb
Yep, it's probably useful only for a quite...

Yep, it's probably useful only for a quite restricted number of scenarios: no competing dma (borders), cpu busy with other tasks like muls and shifts that do not require a lot of memory cycles, or if...
Forum: Coders. Asm / Hardware 04 June 2018, 23:16
Replies: 31
Views: 1,862
Posted By chb
If you optimize for 68k, you could also try to...

If you optimize for 68k, you could also try to use the blitter. I was theorizing about it some time ago here: http://eab.abime.net/showpost.php?p=1172367&postcount=248 (didn't know it has a fancy...
Forum: Coders. General 31 May 2018, 22:57
Replies: 7
Views: 681
Posted By chb
I'm not completely sure what you want to gain by...

I'm not completely sure what you want to gain by this technique. For a color change every 8 pixels you can not use more than 16 colors, so max 4 bitplanes. Also you need to change color 4 for every...
Forum: Coders. Asm / Hardware 03 May 2018, 08:29
Replies: 14
Views: 1,521
Posted By chb
There's an undocumented feature that might be...

There's an undocumented feature that might be handy:
http://eab.abime.net/showthread.php?p=1145422

Basically it gives you a 5-bitplane mode where a 1 in the 5th plane gives you always color 16,...
Forum: Coders. General 24 April 2018, 13:07
Replies: 8
Views: 2,304
Posted By chb
AFAIK CAOS was written (according to Amiga Inc.'s...

AFAIK CAOS was written (according to Amiga Inc.'s spec) by a third-party developer anyway, who did not kept schedule/wanted to renegotiate contracts after Commodore bought Amiga (there are different...
Forum: Coders. Asm / Hardware 14 April 2018, 20:36
Replies: 7
Views: 639
Posted By chb
@robinsonb5: That's a nice method, thanks for...

@robinsonb5: That's a nice method, thanks for sharing!



Hmm, I'd think a HAM8 fade on AGA would be same speed or faster than a HAM6-fade on OCS (both lowres). HAM6 on OCS: ~40,000 chipmem slots...
Forum: Coders. General 07 April 2018, 17:18
Replies: 587
Views: 45,458
Posted By chb
Again: How do you handle this in a multitasking...

Again: How do you handle this in a multitasking environment? Do you expect application programmers to tailor their code (that's maybe written in C or Pascal) to this 32k ram?



That's clear -...
Forum: Coders. General 07 April 2018, 14:48
Replies: 587
Views: 45,458
Posted By chb
How do you want to do that? How do you ensure...

How do you want to do that? How do you ensure that applications use that 32k for their most time critical routines? How do you handle multitasking? Swapping between those 32k and chipram at task...
Forum: Coders. General 07 April 2018, 14:27
Replies: 587
Views: 45,458
Posted By chb
Well, if you have the DRAM technology of that...

Well, if you have the DRAM technology of that time and a 16 bit wide bus, you do not get higher memory bandwidth without considerable effort, like multiple memory subsystems... And 32k of fastram...
Forum: Coders. Asm / Hardware 15 March 2018, 08:43
Replies: 21
Views: 2,079
Posted By chb
Yep, it's not related to blitter c2p, in fact,...

Yep, it's not related to blitter c2p, in fact, britelite's demo wolf3d was using blitter c2p form the beginning, but the rotated chunky buffer came later. AFAIK, he rotates it back to normal layout...
Forum: Coders. General 09 March 2018, 13:46
Replies: 60
Views: 6,275
Posted By chb
Sounds like some seriously crazy hack! :) It...

Sounds like some seriously crazy hack! :) It doesn't involve some fiddling with the blitter modulos by any chance?



I guess we have to just wait for any answer... :D
Forum: Coders. General 07 March 2018, 22:29
Replies: 60
Views: 6,275
Posted By chb
Stephane is still active on the Sega16 forum, so...

Stephane is still active on the Sega16 forum, so should be easy to contact him there:

http://www.sega-16.com/forum/member.php?141357-gasega68k

I'd guess blitter-assisted c2p should be fast...
Forum: Coders. General 06 March 2018, 21:55
Replies: 60
Views: 6,275
Posted By chb
Just a note: Both the "Sonic Kart" and the F-Zero...

Just a note: Both the "Sonic Kart" and the F-Zero clone are by gasega68k/Stephane Dallongeville, which was also active here at eab as "Stef_" (account closed unfortunately).

The Mr. Nutz fly stage...
Forum: Coders. Asm / Hardware 18 January 2018, 18:20
Replies: 18
Views: 740
Posted By chb
meynaf + a/b: I was wrong on a couple of things...

meynaf + a/b: I was wrong on a couple of things in my post #7, I've corrected it, thanks for clarification! But are the aliases like "add.w #$1234,d0" official opcodes? Are they documented, apart...
Forum: Coders. Asm / Hardware 18 January 2018, 15:46
Replies: 18
Views: 740
Posted By chb
@a/b That's not correct, <ea> stands for...

@a/b That's not correct, <ea> stands for <effective address> and can either be a register or a memory address. An immediate value is not an effective address and vice versa. EDIT: It seems it's...
Forum: Coders. Asm / Hardware 18 January 2018, 15:16
Replies: 18
Views: 740
Posted By chb
If I remember correctly, there is no difference;...

If I remember correctly, there is no difference; some assemblers just allow you to use either syntax for convenience.

EDIT: What demolition said. There's no OR.L #$12345678,<EA> officially.
Forum: Coders. Asm / Hardware 18 January 2018, 10:28
Replies: 140
Views: 13,768
Posted By chb
Wow, running in 1.6 -1.9 frames? Totally awesome!...

Wow, running in 1.6 -1.9 frames? Totally awesome! Congratulations, great achievement.



The memory bus is only 16 bit, true, but you always need to fetch the instruction itself, too. That's why...
Forum: Coders. Asm / Hardware 17 January 2018, 11:31
Replies: 17
Views: 957
Posted By chb
Well, of course that's true in some sense, but...

Well, of course that's true in some sense, but the fast sqrt exploits the fact that if you take an integer number i and cast it as an IEEE float (so interpret its binary representation as floating...
Forum: Coders. Asm / Hardware 16 January 2018, 22:07
Replies: 17
Views: 957
Posted By chb
I've known only of the probably more well-known...

I've known only of the probably more well-known fast inverse square root (https://en.wikipedia.org/wiki/Fast_inverse_square_root) before, but they look very similar. But they work on floating point...
Forum: Coders. Asm / Hardware 16 January 2018, 13:07
Replies: 17
Views: 957
Posted By chb
Funny, actually because of that tutorial I was...

Funny, actually because of that tutorial I was asking, as he does not use sqrts in the code AFAICS - except for one instance where he computes deltaDistX rep. deltaDistY and does not apply the...
Forum: Coders. Asm / Hardware 16 January 2018, 11:43
Replies: 17
Views: 957
Posted By chb
Probably for a game a table-based approach is...

Probably for a game a table-based approach is preferable, but are you sure you really need a sqrt for the raycaster?
Forum: Coders. Asm / Hardware 16 January 2018, 10:45
Replies: 17
Views: 957
Posted By chb
Long thread from the Atari forum: ...

Long thread from the Atari forum:
http://www.atari-forum.com/viewtopic.php?t=4984

From "Dr. Dobb's Toolbook of 68000 Programming":...
Forum: Coders. System 15 January 2018, 11:44
Replies: 2
Views: 887
Posted By chb
In the commented exec 1.2 disassembly...

In the commented exec 1.2 disassembly (http://wandel.ca/homepage/execdis/exec_disassembly.txt) there is some explanation (Ctrl-F "HELP"):
Forum: Coders. Asm / Hardware 13 January 2018, 21:27
Replies: 140
Views: 13,768
Posted By chb
That's a wrong assumption, or a misconception...

That's a wrong assumption, or a misconception what "approximately" means in this context. Imagine walking in z-direction in the game. The zoom factor for every column changes and, because of...
Forum: Coders. Asm / Hardware 11 January 2018, 09:05
Replies: 140
Views: 13,768
Posted By chb
Wow, great result, almost steady 25fps on an...

Wow, great result, almost steady 25fps on an A500? Very nice! Even if raycaster + game logic come on top of that - a smaller window or running in 3 frames would be perfectly acceptable for a game....
Forum: Coders. Asm / Hardware 08 January 2018, 15:37
Replies: 140
Views: 13,768
Posted By chb
@kalms: Great estimation! And clever use of...

@kalms: Great estimation! And clever use of movep. I was actually considering that instruction for a moment, but was somehow under the impression that it works only on word bundaries, duh!:banghead
...
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