Prince Of Persia - fastmem

[jotd]

Someone reported that Prince of Persia could be slow at times:


http://mantis.whdload.de/view.php?id=4569



I've computed reloc tables for one UK version you can find it in the drop box attachment of the bug report.


Can someone who's seen the issue test?

[dlfrsilver]

Prince of Persia Amiga is notoriously slow. It's slower than any other versions.

[Superman]

I havent noticed the current slave being any slower than normal to be honest. I did just download this new version but it crashed with an error about disk.1 being compressed with XPK compression and needs an extra file in LIBS:

[Galahad/FLT]

Prince of Persia is heavy on the blitter, over blitting on some screens hence the slow downs, but not where the game is actually crawling.

[jotd]

look at that blitter code

lb_053a2:
	LINK.W	A6,#0			;053a2: 4e560000
	MOVE.L	8(A6),D0		;053a6: 202e0008
	MOVE	SR,D1			;053aa: 40c1
	MOVE	#$2700,SR		;053ac: 46fc2700
	MOVE.L	#$00000001,blitter_done_flag.w	;053b0: 21fc000000011a24
	MOVE.W	D0,BLTSIZE		;053b8: 33c000dff058
	STOP	#$2000			;053be: 4e722000
lb_053c2:
	TST.L	blitter_done_flag.W		;053c2: 4ab81a24
	BEQ.S	lb_053ce		;053c6: 6706
	STOP	#$2000			;053c8: 4e722000
	BRA.S	lb_053c2		;053cc: 60f4
lb_053ce:
	MOVE	D1,SR			;053ce: 46c1
	UNLK	A6			;053d0: 4e5e
	RTS				;053d2: 4e75

That's the first game I see which uses STOP to wait for a blitter interrupt (in the meantime, other code can run). Most of the time it's either blitter interrupt enabled or active wait for blitter end.

Maybe I could patch this code so it uses normal blitwaits. Interrupts are notoriously slow (specially on high end machines, and I suspect that the STOP method (plus all the hacking around with SR) is even slower than chaining blitter interrupts like Shaun Southern does. If another interrupt occurs, the code has to check the flag and loop on STOP until the blitter interrupt clears the flag... I think I can patch this easily.

I have updated the dropbox link to include both slaves: 1 fastmem slave and 1 fastblitter slave (no fastmem). If someone can test and report back (I have unpacked the diskfile too)

[jotd]

anyone could test & report about speed on the new slaves?

[DanyPPC]

Originally Posted by jotd

anyone could test & report about speed on the new slaves?

A1200/030@50Mhz
MiST Latest Minimig AGA Core (11 mips)

Prince of Persia slave 3.4 WHDLoad 18.8

In both machine PoP works good, same speed. It's not slow, for me is standard as other versions.

[lilwshu]

Tested on my A2000/TF536 - 030@50Mhz:

PrinceOfPersia.Slave = same speed as original slave with or without Faster Blitting enabled

PrinceOfPersiaFast.Slave = Considerably faster, similar in speed to MS-DOS version as seen here [ Show youtube player ]

[jotd]

Minimig: not surprising as code in chip is only a speed issue on real amigas.

Glad that it's seen running much faster. It means that it's worth releasing then.

[turrican3]

Do you think that shadow warriors could be enhanced the same way ?
You have slowdowns from time time to time.

[jotd]

I'd say that it's possible, yes.

[turrican3]

Do you think you'll have time to have a look ?

[jotd]

just checked the source code from whdload install and directory is a mess, it contains 6 or more slaves, I don't know which one I should start from. Maybe CFou! knows better (after all he wrote that)

[turrican3]

gunship 2000 could be a cool game to accelerate to.

[turrican3]

a noob question : is it possible to make an adf version ?
A noob question because i'm pretty sure that's impossible if you don't have the source code.

[jotd]

I remember being able to put JST slave of Prince of Persia on a floppy. Runs with 2MB on A500 from floppy. Probably possible to do the same with whdload slave (using JST). The disk image is small, it fits on 880kb without any issues.

So you'd need an .adf of the game running in fast memory. Means you have an accelerated amiga and no HD...

[turrican3]

Myself, i need nothing, i'm playing with winuae.
I didn't think about the solution to use jst, but that's true that someone with an accelerator will often have an hdd or a cf card.

[jotd]

plus you can't save the game...

Currently playing with the fastmem version. I don't see a big different with chipmem version. Maybe in transition screens? or when the game has a lot of work to do? Anyway it works fine and it has to be faster.

[turrican3]

to have a good speed with winuae i need to set "immediate blitter" and then it flies.
Like said flt, it's really blitter intensive.

[alexh]

I'm not particularly knowledgable about patching but can blitter routines be easily detected and patched to equivalent CPU routines?

Ambermoon for example runs a speed test at the start of the game and if it thinks the CPU is faster for blits than the blitter it uses different routines.