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Forum: Nostalgia & memories 10 March 2020, 07:26
Replies: 60
Views: 2,493
Posted By mc6809e
Waiting to buy an A1000 w/monitor at a thrift...

Waiting to buy an A1000 w/monitor at a thrift store for $25 in 2009. Came back a week later and it was gone :(.
Forum: Coders. Asm / Hardware 08 March 2020, 21:24
Replies: 23
Views: 808
Posted By mc6809e
Interesting. Thank you. Simplifies the...

Interesting. Thank you.

Simplifies the logic.

Helps understand how to vertically multiplex sprites using DMA without introducing an unusable scanline between them.

So as long as SPRxPOS and...
Forum: Coders. Asm / Hardware 08 March 2020, 17:39
Replies: 23
Views: 808
Posted By mc6809e
From the reference manual: ...

From the reference manual:

http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node02D6.html

Notice the SR latch is reset when SPRxCTL is accessed disabling the sprite and access to...
Forum: support.Games 26 January 2020, 01:38
Replies: 93
Views: 5,515
Posted By mc6809e
I think The Ancient Art of War was originally for...

I think The Ancient Art of War was originally for the Mac.

Should be easy to get it to run on the Amiga.
Forum: Coders. Asm / Hardware 16 January 2020, 19:34
Replies: 18
Views: 656
Posted By mc6809e
Interrupt latency depends on when interrupt pins...

Interrupt latency depends on when interrupt pins are sampled and this is instruction dependent.

Worst case is MOVE.L all regs followed by DIVS -- over 300 cycles.

MOVEM.L samples pins at...
Forum: Coders. Asm / Hardware 14 January 2020, 23:43
Replies: 21
Views: 1,140
Posted By mc6809e
The blitter can actually compute any computable...

The blitter can actually compute any computable function since it can implement cellular automata and there exist universal CA that can compute anything a Turing machine can.

An interesting...
Forum: Nostalgia & memories 14 January 2020, 00:21
Replies: 53
Views: 3,038
Posted By mc6809e
The CIAs provide resources for syncing the CPU...

The CIAs provide resources for syncing the CPU with the display. That and cycle counting can allow the CPU to write to chip registers at specific times relative to the beam. There is potential with...
Forum: Nostalgia & memories 13 January 2020, 19:40
Replies: 53
Views: 3,038
Posted By mc6809e
One positive thing about Amiga sprites is that...

One positive thing about Amiga sprites is that they are available with HAM.

Still, the limited support means this is hard to take advantage of.

With slightly better sprite support a nice...
Forum: Coders. Asm / Hardware 13 January 2020, 19:33
Replies: 21
Views: 1,140
Posted By mc6809e
Skip allows for conditional execution. The...

Skip allows for conditional execution.

The logic of it can be confusing.

Often the instruction being skipped is a strobe to change the flow of execution. In effect this causes execution of the...
Forum: Nostalgia & memories 12 January 2020, 16:27
Replies: 53
Views: 3,038
Posted By mc6809e
The layout of sprite management bits in register...

The layout of sprite management bits in register space was a bit flubbed, IMO.

Manual mode would have been much more useful if horizontal position information for each sprite had been in a single...
Forum: Coders. Asm / Hardware 12 January 2020, 03:42
Replies: 6
Views: 733
Posted By mc6809e
Might setting SING help here? Something I've...

Might setting SING help here? Something I've wondered about is whether or not with SING writes are reduced. If so, then there might be a small amount of time saved blanking lines with slope <1 and...
Forum: Coders. Asm / Hardware 04 May 2019, 02:15
Replies: 14
Views: 674
Posted By mc6809e
If you time it correctly, you should be able to...

If you time it correctly, you should be able to start blitting a little before display fetch ends. Just make sure display fetch wins the race for access to the playfield.

And if you use...
Forum: Coders. Asm / Hardware 11 April 2019, 03:10
Replies: 20
Views: 2,829
Posted By mc6809e
For copying you can't beat the blitter with the...

For copying you can't beat the blitter with the 68000.

It's another story with clearing. That's much more complicated.

Clearing by the blitter uses one idle cycle and one write cycle. Because...
Forum: Coders. Asm / Hardware 08 April 2019, 02:50
Replies: 30
Views: 4,139
Posted By mc6809e
Good question. Some of the better informed around...

Good question. Some of the better informed around here might be able to tell you. I think there are a few tricks typically done for efficiency that might fail.



Either line 0 or line 1,...
Forum: Coders. Asm / Hardware 08 April 2019, 02:12
Replies: 30
Views: 4,139
Posted By mc6809e
Very nice! Looks awesome!

Very nice! Looks awesome!
Forum: Coders. Asm / Hardware 07 April 2019, 03:19
Replies: 30
Views: 4,139
Posted By mc6809e
You seem really committed! Want a challenge? How...

You seem really committed! Want a challenge? How about trying to make a copper-driven blitter queue that even crosses frame boundaries? In other words, it works even when VBLANK resets the copper...
Forum: Nostalgia & memories 14 February 2019, 03:56
Replies: 76
Views: 8,053
Posted By mc6809e
Uhg. So you think the sinc function is simple?...

Uhg. So you think the sinc function is simple? It's not even finite!

But of course we don't really need the entire sinc function. But we still need enough of it to convolve it with the sample. And...
Forum: Coders. General 30 January 2019, 02:57
Replies: 15
Views: 5,576
Posted By mc6809e
I'd love to see a 3d game that uses the blitter...

I'd love to see a 3d game that uses the blitter to the max. I mean of course a completely generic blitter queue controlled by the copper. It is possible -- even while blits are running across frames.
Forum: Nostalgia & memories 30 January 2019, 02:52
Replies: 76
Views: 8,053
Posted By mc6809e
A problem with digital audio, IMHO, is with the...

A problem with digital audio, IMHO, is with the belief that because we have all the samples necessary for perfect reconstruction we get perfect reconstruction when those samples are output through...
Forum: support.Hardware 26 January 2019, 03:03
Replies: 8
Views: 646
Posted By mc6809e
I put a 68010 in an A500. Very little speed up...

I put a 68010 in an A500. Very little speed up and too many problems for it to be worth the bother.
Forum: Retrogaming General Discussion 08 January 2019, 04:16
Replies: 147
Views: 10,586
Posted By mc6809e
This misunderstanding has been going on for ages....

This misunderstanding has been going on for ages.

The problem is with the loose definition of "sample". Paula may be OR MAY NOT BE outputting a sample when it generates sounds.

What Paula does...
Forum: Retrogaming General Discussion 22 December 2018, 03:06
Replies: 52
Views: 3,891
Posted By mc6809e
If you're using blitz basic for blits then, yeah,...

If you're using blitz basic for blits then, yeah, the blitter is going to appear slow.

And if you're blitting and waiting and then blitting and waiting and on and on, it's going to appear to be...
Forum: Coders. Asm / Hardware 08 December 2018, 03:56
Replies: 1,000
Views: 45,463
Posted By mc6809e
Two things. First, if you're going to count the...

Two things. First, if you're going to count the loading of addresses, you have to count the loading of the segment registers. That's going to cost instructions.

But that's silly anyway. The...
Forum: Coders. AMOS 04 December 2018, 03:44
Replies: 6
Views: 2,491
Posted By mc6809e
Sprites are probably best if treated like their...

Sprites are probably best if treated like their own, narrow, relatively static, playfield as an overlay, like for scores, lives left, power, etc.
Forum: Coders. Asm / Hardware 25 November 2018, 03:59
Replies: 1,000
Views: 45,463
Posted By mc6809e
It occurs to me that a slight modification to the...

It occurs to me that a slight modification to the emulator's cpu code that removes the idle cycles during branch instructions might give a visual idea of the extent to which the 68K falls short using...
Forum: Coders. Asm / Hardware 18 November 2018, 17:27
Replies: 1,000
Views: 45,463
Posted By mc6809e
Lots of data from Intel concerning the 8086 vs...

Lots of data from Intel concerning the 8086 vs 68000 vs 80286:

http://www.bitsavers.org/components/intel/80186/210826_iAPX_186_286_Benchmark_Report_Oct82.pdf

Several of their own benchmarks...
Forum: Coders. Asm / Hardware 17 November 2018, 19:52
Replies: 1,000
Views: 45,463
Posted By mc6809e
Yeah, the three refresh DMA cycles at the...

Yeah, the three refresh DMA cycles at the beginning of each scanline is going to cause at least one instruction to take 8 cycles instead of 6.

Still, it's nice seeing confirmation that most of...
Forum: Coders. Asm / Hardware 17 November 2018, 03:25
Replies: 1,000
Views: 45,463
Posted By mc6809e
What about for zero planes, like during the...

What about for zero planes, like during the overscan and HBlank and VBlank?

Dang it. Now I'm getting sucked into another ST vs Amiga blackhole.

Ignoring that, I think the bus access timing...
Forum: Coders. Asm / Hardware 16 November 2018, 02:46
Replies: 1,000
Views: 45,463
Posted By mc6809e
Except that a memory cycle can start on a 2 cycle...

Except that a memory cycle can start on a 2 cycle boundary. It still takes 4 cycles to complete the access but an instruction can actually take a multiple of 2 cycles.

It's one thing that makes...
Forum: Coders. Asm / Hardware 15 November 2018, 03:48
Replies: 1,000
Views: 45,463
Posted By mc6809e
Yeah, you're right, of course. Terje has...

Yeah, you're right, of course.

Terje has said that you could very well estimate the speed of most code by simply counting the total number of memory accesses needed.

Anyone really interested...
Forum: Coders. Asm / Hardware 15 November 2018, 03:44
Replies: 1,000
Views: 45,463
Posted By mc6809e
This might already be somewhere around here but I...

This might already be somewhere around here but I thought I'd post it as it seems somewhat relevant:

http://nemesis.hacking-cult.org/MegaDrive/Documentation/Yacht.txt

Amazing document...
Forum: Coders. Asm / Hardware 12 November 2018, 02:56
Replies: 1,000
Views: 45,463
Posted By mc6809e
I'm surprised no one mentioned a potentially...

I'm surprised no one mentioned a potentially difficult problem using x86 segments and C: pointer aliasing issues.

It's entirely possible for two pointers to point to precisely the same memory...
Forum: Coders. Asm / Hardware 04 November 2018, 02:17
Replies: 1,000
Views: 45,463
Posted By mc6809e
Instruction prefetch on the 68k is hard coded....

Instruction prefetch on the 68k is hard coded. Each instruction, besides performing its primary operation, will prefetch the first word of the next instruction in the same way every time. This means...
Forum: Hardware mods 29 September 2018, 03:14
Replies: 518
Views: 125,220
Posted By mc6809e
Back in the day I used the piggy-back method to...

Back in the day I used the piggy-back method to bring my A500 to 1Meg.

I can't remember the details but basically I soldered another 16 chips on top of the 16 already on the motherboard, making...
Forum: support.Apps 18 April 2015, 02:58
Replies: 17
Views: 3,382
Posted By mc6809e
I wonder what these videos would look like if the...

I wonder what these videos would look like if the Amiga designers had stuck with using an YIQ or YUV scheme instead of RGB. Probably much better (assuming proper coding).

Maybe they should have...
Forum: support.Hardware 10 March 2015, 12:15
Replies: 42
Views: 4,264
Posted By mc6809e
The first is just a student's report drawn from...

The first is just a student's report drawn from other sources. Nothing there really.

The second is a test of multipath, but at the smallest tested interval of 2 microseconds, the interfering path...
Forum: support.Hardware 09 March 2015, 20:42
Replies: 42
Views: 4,264
Posted By mc6809e
The idea that the OFDM of DVB-T is multipath...

The idea that the OFDM of DVB-T is multipath resistant is mostly a myth.

It should be obvious that mixing the OFDM signal with a carrier re-narrows the signal and the multipath advantage almost...
Forum: support.Hardware 07 March 2015, 03:36
Replies: 42
Views: 4,264
Posted By mc6809e
Nearly the same signal. The only thing PAL...

Nearly the same signal.

The only thing PAL did was invert the chroma phase of every other line so that any shift in one line could be compensated for by the next line.

It did result in reducing...
Forum: support.Hardware 06 March 2015, 19:39
Replies: 42
Views: 4,264
Posted By mc6809e
PAL flicker is miserable. I don't know how anyone...

PAL flicker is miserable. I don't know how anyone can stand it.
Forum: Amiga scene 02 March 2015, 21:59
Replies: 34
Views: 11,322
Posted By mc6809e
Excellent, Bean! Thanks!

Excellent, Bean! Thanks!
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