TweetFollow Us on Twitter

Aug 99 Tips

Volume Number: 15 (1999)
Issue Number: 8
Column Tag: Tips & Tidbits

Tips and Tidbits

by Jeff Clites, tips@mactech.com

Blistering Blitting

The June issue of MacTech highlighted some ways to move pixels around but there was no mention of a little-known PPC ASM instruction that can be used to speed pixel blitting (and all memory moving functions for that matter) called lmw/stmw.

When the data is aligned, it takes 4 cycles to execute a normal move memory. These two instructions are very powerful because they take 3 + n cycles to move n words. Hence each additional move only takes 1 cycle. This instruction works differently on different PPCs. The 601 treats these instruction like multiple lwa while the 603e, 604 and, G3 treat the instruction like a multimove.

There are a few restrictions on the following code:

  1. It works fastest when the baseAddrs are aligned.
  2. The code is for 8-bit pixels (tip: change r23 to 12 for 16 bit pixels and to 6 for 32 bit pixels).
  3. The width must be a multiple of 24 for 8 bit pixels (12 for 16 bit pixels, and 6 for 32 bit pixels). If it isn't there will be pixel overwriting. Most of the overwrite will be overwritten with the next scan line. You have been warned! (Any destination world should have a few more words in its baseAddr.)
  4. This assumes the same palette for the source and destination worlds (in 8-bit mode).
  5. This assumes the same depth for the source and destination worlds.

The following is an example of how to move pixels three times faster than the fastest method presented in Fast Blit Strategies.

export SpeedCopy[DS]
export .SpeedCopy[PR]
toc
	tc SpeedCopy[TC],	SpeedCopy[DS]	;TOC entry "SpeedCopy" for
																	;transition vector "SpeedCopy"
		csect	SpeedCopy[DS]			 		;Define transition vector "SpeedCopy"
		dc.l		.SpeedCopy[PR]	 				;Pointer to code
		dc.l		TOC[tc0]								;Pointer to TOC
		dc.l		0
# Prolog: SpeedCopy
;void SpeedCopy(long height, long width, long srcRowbytes,
;		unsigned long *dest, long destRowbytes,	unsigned long* src);
		csect	.SpeedCopy[PR]			;Prolog begins here
		;r3	= dest.height
		;r4	= dest.width
		;r5	= dest.rowbytes
		;r6	= dest.baseAddr
		;r7	= src.rowbytes
		;r8	= src.baseAddr
		stmw		r22,-36(SP)					;store temp register space
		li			r22, 1
		li			r23, 24
@lineLoop
		mr			r12,r4							;x = dest.width
		mr			r10,r6							;tmpdest = dest
		mr			r11,r8							;tmpsrc = src
@pixelLoop:
		lmw		r25,0(r11)					;Move 4 + 4 + 4 + 4 + 4 + 4 from 
														;tempSource to r25 thru r31
		subf.	r12,r23,r12					;Subtract num Pixels from total, test against 0
		addi		r11,r11,24					;Add pixel width to tempSource even for	
														;different size pixels
		stmw		r25,0(r10)					;Move pixels from r25 thru r31 to screen
		addi		r10,r10,24					;Add pixel width to dest even for different
														;size pixels
		bgt		@pixelLoop					;Loop if the subtraction is greater than 0
		subf.	r3, r22, r3				;Subtract one line from height, test against 0
		add		r8,r8,r7						;Add src.rowbytes to src.baseaddr
		add		r6,r6,r5						;Add dest.rowbytes to dest.baseaddr
		bne		@lineLoop					;Loop if height not equal to 0
		lmw		r22,-36(SP)					;Restore register space
		blr
end

With a few changes this code can pixel double, copy every other line, or both.

The best way to make a machine go faster is to make it do less. This is one of only a handful of cases where you can do more with less.

Brad Anderson anderson@rpmmusic.com

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Ellipsis - Touch. Explore. Survive. (...
Ellipsis - Touch. Explore. Survive. 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »
Ys Chronicles II (Games)
Ys Chronicles II 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: After a hard fight to recover the six sacred books in Ys Chronicles I, Adol is back for a sequel! | Read more »
FINAL FANTASY Ⅸ (Games)
FINAL FANTASY Ⅸ 1.0.4 Device: iOS Universal Category: Games Price: $16.99, Version: 1.0.4 (iTunes) Description: ==========●Special sale price for the FINAL FANTASY IX release! ●20% off from February 10 to February 21, 2016... | Read more »
Tennis Club Story (Games)
Tennis Club Story 1.03 Device: iOS Universal Category: Games Price: $4.99, Version: 1.03 (iTunes) Description: Aim for the ace position of tennis club prestige in this simulation! Your leadership decides if players make it to the big... | Read more »
Juggernaut Wars guide - How to use skill...
Juggernaut Warsis a brand new auto-RPG on iOS and Android that challenges you to build a team of heroes, send them out into various different missions to defeat waves of heroes, and level them up to increase their power. The actual combat itself... | Read more »
Check out the new Pirate Attack update i...
Love pirates and board games? Well, you'll love the new Pirate Attack themed update that just launched in Game of Dice. It adds a bunch of new content themed around pirates, like an all new event map based on a pirate ship which revamps the toll... | Read more »
Splash Cars guide - How to paint the tow...
Splash Cars is an arcade driving game that feels like a hybrid between Dawn of the Plow and Splatoon. In it, you'll need to drive a car around to repaint areas of a town that have lost all of their color. Check out these tips to help you perform... | Read more »
The best video player on mobile
We all know the stock video player on iOS is not particularly convenient, primarily because it asks us to hook a device up to iTunes to sync video in a world that has things like Netflix. [Read more] | Read more »
Four apps to help improve your Super Bow...
Super Bowl Sunday is upon us, and whether you’re a Panthers or a Broncos fan you’re no doubt gearing up for it. [Read more] | Read more »
LooperSonic (Music)
LooperSonic 1.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0 (iTunes) Description: LooperSonic is a multi-track audio looper and recorder that will take your loops to the next level. Use it like a loop pedal to... | Read more »

Price Scanner via MacPrices.net

App Annie Reveals Future of the App Economy:...
App Annie, a San Francisco based mobile app data and insights platform, has launched its first comprehensive app economy forecast. This new offering will provide brands, agencies, investors and app... Read more
Apple restocks Certified Refurbished Mac mini...
Apple has restocked Certified Refurbished 2014 Mac minis, with models available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz Mac mini: $419 $... Read more
What iPad Pro Still Needs To Make It Truly Pr...
I love my iPad Air 2. So much that I’m grudgingly willing to put up with its compromises and limitations as a production tool in order to take advantage of its virtues. However, since a computer for... Read more
21-inch 3.1GHz 4K on sale for $1399, $100 off...
B&H Photo has the 21″ 3.1GHz 4K iMac on sale $1399 for a limited time. Shipping is free, and B&H charges NY sales tax only. Their price is $100 off MSRP: - 21″ 3.1GHz 4K iMac (MK452LL/A): $... Read more
Apple price trackers, updated continuously
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: - 15″... Read more
Save up to $240 with Apple Certified Refurbis...
Apple is now offering Certified Refurbished 12″ Retina MacBooks for up to $240 off the cost of new models. Apple will include a standard one-year warranty with each MacBook, and shipping is free. The... Read more
Apple refurbished 13-inch Retina MacBook Pros...
Apple has Certified Refurbished 13″ Retina MacBook Pros available for up to $270 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free: - 13″ 2.7GHz... Read more
Apple refurbished Time Capsules available for...
Apple has certified refurbished Time Capsules available for $120 off MSRP. Apple’s one-year warranty is included with each Time Capsule, and shipping is free: - 2TB Time Capsule: $179, $120 off - 3TB... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
Apple has Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.5GHz MacBook Pros... Read more
Apple refurbished 15-inch Retina MacBook Pros...
Apple has Certified Refurbished 2015 15″ Retina MacBook Pros available for up to $380 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free: - 15″ 2... Read more

Jobs Board

Lead Engineer - *Apple* OSX & Hardware...
Lead Engineer - Apple OSX & Hardware **Job ID:** 3125919 **Full/Part\-Time:** Full\-time **Regular/Temporary:** Regular **Listed:** 2016\-02\-10 **Location:** Cary, Read more
Simply Mac *Apple* Specialist- Service Repa...
Simply Mac is the largest premier retailer of Apple products in the nation. In order to support our growing customer base, we are currently looking for a driven Read more
Infrastructure Engineer - *Apple* /Mac - Rem...
…part of a team Requires proven problem solving skills Preferred Additional: Apple Certified System Administrator (ACSA) Apple Certified Technical Coordinator (ACTC) Read more
Lead Engineer - *Apple* OSX & Hardware...
Lead Engineer - Apple OSX & Hardware **Job ID:** 3125919 **Full/Part\-Time:** Full\-time **Regular/Temporary:** Regular **Listed:** 2016\-02\-10 **Location:** Cary, Read more
*Apple* System Analyst - ATOS IT Services...
Apple System AnalystReference no.198783CountryUSARegionUS - CALIFORNIACityUS - CALIFORNIA - BURBANKPosition TypeProfessionalJob AreaIT SupportJob TypeFull Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.