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Old 19 April 2007, 21:06   #1
pmc
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Hidden Amiga 68000 opcode?

I've been watching the Razor 1911 demo Vertical Insanity.

The scrolltext talks about a hidden 68000 instruction that can be used on the Amiga only to move words into the custom chip registers called movef - 68000 opcode $3222. It claims that this move command does this very quickly.

Does anyone know if this is true? If it is, is it actually any use, and how would I go about using it from my assembler? Devpac 3 complains about an unrecognised instruction if I type in movef...
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Old 19 April 2007, 21:15   #2
musashi5150
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That's a hoax my friend That opcode is pure fiction. Their bars are done using a HAM trick.
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Old 19 April 2007, 21:26   #3
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Those cheeky scamps! I had a feeling it would turn out to be bullshit... At least I know - nice one musashi5150 - hey, hang on a minute, I spelt your name right!
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Old 19 April 2007, 22:18   #4
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Easiest way to "confirm" this is by trying to disassemble $3222...
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Old 20 April 2007, 10:11   #5
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Quote:
Originally Posted by pmc
I've been watching the Razor 1911 demo Vertical Insanity.The scrolltext talks about a hidden 68000 instruction that can be used on the Amiga only to move words into the custom chip registers called movef - 68000 opcode $3222. It claims that this move command does this very quickly.
There is a C64 demo homage (or was it the other way around?) In the scroll text they too have found a "secret opcode" on the C64

http://www.pouet.net/prod.php?which=15401

You need to read the scroll text in the secret part of the Razor 1911 Amiga Vertial Insanity demo. Hold right mouse button while the demo decrunches for an alternative scroller and a rastertime counter.

Last edited by alexh; 22 April 2007 at 21:44.
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Old 20 April 2007, 17:16   #6
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Hmmm, interesting... Thanks for the info alexh.

Quote:
You need to read the scroll text in the secret part of the demo. Hold right mouse button while the demo decrunches for an alternative scroller and a rastertime counter.
I'll try that out.
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Old 20 April 2007, 20:43   #7
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Just accessed the hidden part and read the real explanation for how the 'vertical copper bars' were done, very interesting and quite clever really...
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Old 22 April 2007, 16:50   #8
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Right mouse on the c64

.
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Old 22 April 2007, 18:44   #9
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@mr_0rga5m - err... no. When I first read alexh's post I read it like that. He means press the rmb when the Amiga demo's loading...
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Old 08 May 2007, 19:34   #10
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The 6502 processor actually had quite a few more or less undocumented opcodes which did lots of wierd stuff. Wonder if this could be the case on the 680x0 aswell..? hmm..
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Old 08 May 2007, 21:37   #11
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No. They were taking the piss. Joking, fooling around.
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Old 08 May 2007, 22:58   #12
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In the demo they were joking but could oRBIT have a point - aside from the bullshit in the demo are there actually any undocumented opcodes?
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Old 09 May 2007, 10:02   #13
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I don't think there are... but Toni Wilen would be the man to ask

There was a thread along a similar line about quirky 68K aspects a while back, http://eab.abime.net/showthread.php?t=23315 might be worth a little look if you're interested.
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Old 09 May 2007, 11:54   #14
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Thanks mate, as usual, you are 'da man'!
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Old 09 May 2007, 16:34   #15
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I am quite sure the answer is "no".

68000+ (and all "modern" CPUs) have illegal instruction exception (or similar feature), 6502 don't. Another difference is that 68000 internally executes microcode (every 68k instruction is internally executed using few internal basic microcode instructions)

Check 68000 patents, they are most interesting, they even include (very unreadable) microcode listing.(http://patft.uspto.gov/netahtml/PTO/srchnum.htm Patent numbers: 4342078 and 4296469)
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Old 09 May 2007, 17:21   #16
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Ooooo.

I once did a 68000 in VHDL but I did it as a non microcoded state machine.

It was a lot bigger (perhaps 8x or 9x the size) than the 68000 transistors (17k gates).

To match timing on some instructions I had to do some horrible cycle wait states.

It was never even close to cycle accurate, much like the existing attempts at a 68000 in HDL.
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Old 10 May 2007, 08:13   #17
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@Alexh

I don't care how many gates it uses. I just wanna know how fast is it?

Can it go faster than 50 Mhz?

I don't want it to be cycle accurate to a slow lame 68000 from 1978.
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Old 10 May 2007, 12:45   #18
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Quote:
Originally Posted by StrategyGamer
@Alexh
I don't care how many gates it uses. I just wanna know how fast is it?
Can it go faster than 50 Mhz?
According to Synopsys it could run at over 300MHz at 0.13um. All I need now is $2,000,000 for a set of masks

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I don't want it to be cycle accurate to a slow lame 68000 from 1978.
I do... otherwise Amiga stuff (and especially Atari ST stuff) wont work.
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Old 13 May 2007, 23:52   #19
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Quote:
Originally Posted by Toni Wilen
Easiest way to "confirm" this is by trying to disassemble $3222...
What is this supposed to confirm? They spoke about an opcode they have found, not some memory location. It's the same as if you would try to disassemble $4e71 and expect to find nop instruction there...
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Old 14 May 2007, 09:43   #20
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@StingRay - I think Toni means that $3222 is the hex value of the machine language opcode rather than a memory location... For example, a real instruction like:

moveq #1,d1

is actually encoded as

0111001000000001 (or $7201 in hex)

by your assembler for the processor to then execute...

At least I think that's what Toni means!
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