Target system and code speed

h0ffman · 07 June 2011, 14:40

Just wondering about target systems and code structure today. Mainly because I'm thinking of doing a demo for the stock A1200.

I've learned so far that on a standard 68000, as there are no caches, rolling out loops gives the best speed improvement because theres no cache and every instruction counts!

However, the 68020 has a CPU cache. Does this mean that rolled out loops could actually impair performance? Can't remember the cache size on the 020, but I'm guessing if your loop is less than the size of the cache, it would blaze through it faster than a rolled out loop?

StingRay · 07 June 2011, 15:30

Quote:

Originally Posted by h0ffman

However, the 68020 has a CPU cache. Does this mean that rolled out loops could actually impair performance?

Yes.

Quote:

Originally Posted by h0ffman

Can't remember the cache size on the 020

68020 has 256 byte instruction cache.

Quote:

Originally Posted by h0ffman

but I'm guessing if your loop is less than the size of the cache, it would blaze through it faster than a rolled out loop?

That's correct.

h0ffman · 07 June 2011, 16:31

Cheers, will keep that in mind.

Photon · 24 June 2011, 00:07

Demos for stock Amigas \o/

Nice to see this, and a showcase of correct thinking paired with necessary knowledge

Djay · 24 June 2011, 00:15

Yes!

It would great to get see a new demo for stock A1200, it should have its own section at demo parties! I like to see how far people can push the hardware!

pmc · 24 June 2011, 08:33

I agree 100% - stock Amiga demos rule.

While accelerator cards are cool, it's their pervasive influence that's pushed Amiga demos far too far towards trying to clone PC demos in my opinion.

Is an Amiga demo largely developed in C or C++ and running a software chunky graphics mode *really* an Amiga demo...?

What's wrong with an Amiga demo *being* an Amiga demo with bitplane graphics and using the custom chips to give the extra juice needed to make the effects run up to speed...?

We should follow the example of the C64 scene and make more demos for the stock machines!

Accordingly, as you may have guessed (

) I'll be looking forward to h0ff's stock A1200 demo!

Skope · 24 June 2011, 09:28

Quote:

Originally Posted by pmc

I agree 100% - stock Amiga demos rule.

The way nature intended, indeed. I remember when I got my first A1200 back in 1996-ish, it was damn near impossible to find anything that would run on my vanilla machine. I had my A500 totally unexpanded between 1988 and 1992-ish and got by just fine.

h0ffman · 25 June 2011, 00:00

I reckon it should be called "no accelerator required!". Haha

07 June 2011, 14:40	#1
h0ffman Registered User Join Date: Aug 2008 Location: Salisbury Posts: 774	Target system and code speed Just wondering about target systems and code structure today. Mainly because I'm thinking of doing a demo for the stock A1200. I've learned so far that on a standard 68000, as there are no caches, rolling out loops gives the best speed improvement because theres no cache and every instruction counts! However, the 68020 has a CPU cache. Does this mean that rolled out loops could actually impair performance? Can't remember the cache size on the 020, but I'm guessing if your loop is less than the size of the cache, it would blaze through it faster than a rolled out loop?

24 June 2011, 08:33	#6
pmc gone Join Date: Apr 2007 Location: completely gone Posts: 1,596	I agree 100% - stock Amiga demos rule. While accelerator cards are cool, it's their pervasive influence that's pushed Amiga demos far too far towards trying to clone PC demos in my opinion. Is an Amiga demo largely developed in C or C++ and running a software chunky graphics mode really an Amiga demo...? What's wrong with an Amiga demo being an Amiga demo with bitplane graphics and using the custom chips to give the extra juice needed to make the effects run up to speed...? We should follow the example of the C64 scene and make more demos for the stock machines! Accordingly, as you may have guessed () I'll be looking forward to h0ff's stock A1200 demo!

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07 June 2011, 16:31	#3
h0ffman Registered User Join Date: Aug 2008 Location: Salisbury Posts: 774	Cheers, will keep that in mind.

24 June 2011, 00:07	#4
Photon Moderator Join Date: Nov 2004 Location: Eksjö / Sweden Posts: 5,698	Demos for stock Amigas \o/ Nice to see this, and a showcase of correct thinking paired with necessary knowledge

24 June 2011, 00:15	#5
Djay 95th User Join Date: May 2001 Location: Brighton/UK Age: 48 Posts: 3,120	Yes! It would great to get see a new demo for stock A1200, it should have its own section at demo parties! I like to see how far people can push the hardware!

25 June 2011, 00:00	#8
h0ffman Registered User Join Date: Aug 2008 Location: Salisbury Posts: 774	I reckon it should be called "no accelerator required!". Haha

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