Concurrency penalty

Ask anything your want about the 32X Mushroom programming.

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ob1
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Posts: 451
Joined: Wed Dec 06, 2006 9:01 am
Location: Aix-en-Provence, France

Concurrency penalty

Post by ob1 » Sun May 16, 2021 4:36 pm

Hello to you all.
Working on a personnal project, I was able to benchmark the penalty of the Master / Slave concurrency Bus Access.
As you know, when Master and Slave both want to access the bus, the Master has the priority, and the Slave can access the bus when it receives the permission to do it.
My test code was:

Code: Select all

!loop:
	MOV.W	R12,@R1    ; Write to DRAM
	ADD	#1,R9
	CMP/HI	R9,R13
	BF/S	!rarely
	ADD	#2,R1
	DT	R11
	BF/S	!loop
	MOV.W	@R10+,R12    ; Read from SDRAM
Running this same slice of code on both Master and Slave gave me this result:
concurrency between Master and Slave makes the Slave between 6 an 10% slower.
Your mileage may vary.
Tested on real PAL hardware.

I thought this could help ^^
SuperVDP
Paprium - 68000 Assembly
??? - SH2 Assembly

Chilly Willy
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Posts: 2856
Joined: Fri Aug 17, 2007 9:33 pm

Re: Concurrency penalty

Post by Chilly Willy » Sun May 16, 2021 9:39 pm

I like these in-depth analyses you're doing on the 32X. Makes some oddities about the hardware easier to understand, and maybe deal with.

djcouchycouch
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Posts: 707
Joined: Sat Feb 18, 2012 2:44 am

Re: Concurrency penalty

Post by djcouchycouch » Fri May 21, 2021 4:47 pm

WIth my 32x experiments, these are definitely related to my interests! It's great!

ob1
Very interested
Posts: 451
Joined: Wed Dec 06, 2006 9:01 am
Location: Aix-en-Provence, France

Re: Concurrency penalty

Post by ob1 » Fri May 21, 2021 8:21 pm

Glad it helps ^^
SuperVDP
Paprium - 68000 Assembly
??? - SH2 Assembly

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