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Low Performance Falcon

Posted: Tue Jul 09, 2019 7:35 am
by wietze
Hi there guys,

I found myself in the following situation (I only realized this week):
- My Atari Falcon (030, 14mb ram) underperforms. I realized this when running New Beat's `joy' demo. I noticed that the machine takes more than 1 frame to calculate the demo ( http://frummel.org/~weedz/atari/examples/joy.mp4 ).
- Further investigation, by running GemBench lead to the results where I find `outlier' values for ROM and RAM access times (~50-60% instead of 100%).
http://frummel.org/~weedz/atari/examples/gembench.jpg
- I did investigate the RAM and ROM timing settings, but not finding anything out of the ordinary http://frummel.org/~weedz/atari/examples/waitstates.jpg

Background:
- Initially this board had the Mighty Sonic 32 fitted http://wiki.newtosworld.de/index.php?ti ... y_Sonic_32 and the PDF at https://docs.dev-docs.org/htm/search.php?find=_h and it was removed since it introduced incompatability with some demos.

I have only limited amount of knowledge about electronics, but I know some people in the community that are way more knowledgeable than me, that are willing to help me with poking the board. What I am looking for is suggestions and comments such that I can investigate as good as possible to find out whats causing this problem.

Future reference:
- A ct60e is on its way, but I reckon its a better idea to sort this out before getting that mod installed.

Hopefully you guys can help me bring this bird up to speed.

Re: Low Performance Falcon

Posted: Tue Jul 09, 2019 8:45 am
by exxos
Have you checked the CPU clock.. Sounds like your falcon is stuck in 8mhz.

Re: Low Performance Falcon

Posted: Tue Jul 09, 2019 9:38 am
by wietze
exxos wrote:
Tue Jul 09, 2019 8:45 am
Have you checked the CPU clock.. Sounds like your falcon is stuck in 8mhz.
How do I check this?

Re: Low Performance Falcon

Posted: Tue Jul 09, 2019 10:41 am
by exxos
You could try SI.CPX I think I used it on the Falcon to test GB6.. but it was a couple years ago now...

SI.zip
(4.22 KiB) Downloaded 37 times

No idea if SYSINFO reports correct CPU speed on Falcon or not... Quickest way is just to check on a scope the clock line to CPU and see if its running 8MHz, but I assume that is the case anyway.

Also are you clean booting with a blank floppy in the drive ? (also no hard drives connected). There may be some software causing the 8MHz to be set.

Re: Low Performance Falcon

Posted: Tue Jul 09, 2019 6:52 pm
by wietze
Nembench report:

Code: Select all

Integer multiply (16bit) -> 0.5339 Mips (~87%)
Integer divide (16bit) -> 0.330 Mips (~91%)
Linear (stalled) integer -> 2.533 Mips (~31%)
Interleaved (piped) integer -> 2.533 Mips (~31%)

Float multiply (64bit) -> 0.242 MegaFlops (~91%)
Float divide (64bit) -> 0.161 MegaFlops (~93%)
Linaear (stalled) float -> 0.349 MegaFlops (~65%)
Interleaved (piped) flat -> 0.348 MegaFlops (~65%)

16 bit read (100% hit) -> 2.621 MByte/sec (~33%)
16 bit write (100% hit) -> 2.997 MByte/sec (~49%)
32 bit read (100% hit) -> 3.685 MByte/sec (~23%)
32 bit write (100% hit) -> 4.068 MByte/sec (~61%)

Linear 32 bit read (ST-Ram) -> 3.673 MByte/sec (~69%)
Linear 32 bit write (ST-Ram) -> 3.938 MByte/sec (~61%)
Linear 32 bit copy (ST-Ram) -> 2.294 MByte/sec (~71%)

Re: Low Performance Falcon

Posted: Tue Jul 09, 2019 6:58 pm
by wietze
exxos wrote:
Tue Jul 09, 2019 10:41 am
No idea if SYSINFO reports correct CPU speed on Falcon or not... Quickest way is just to check on a scope the clock line to CPU and see if its running 8MHz, but I assume that is the case anyway.
I tested with sysinfo, and it tells me that the frequency of the falcon is at 16 mhz.

Re: Low Performance Falcon

Posted: Tue Jul 09, 2019 9:10 pm
by wietze
Some further research turns out that hte machine performs the same performance wise with cache frozen and disabled for a series of dbra loops. So perhaps its a cache issue (that its being grounded for example).

I need to find out which pin of the cpu this is.

Re: Low Performance Falcon

Posted: Tue Jul 09, 2019 9:22 pm
by exxos
Datacache doesn't have much impact in GB6 results. Instruction cache gives about 25% boost. So I think your caches are fine. You need to scope the CPU clock and see if its running at 8MHz.

Re: Low Performance Falcon

Posted: Tue Jul 09, 2019 10:29 pm
by wietze
exxos wrote:
Tue Jul 09, 2019 9:22 pm
Datacache doesn't have much impact in GB6 results. Instruction cache gives about 25% boost. So I think your caches are fine. You need to scope the CPU clock and see if its running at 8MHz.
Well. I got 2 programs, one that runs a loop from icache; and does the same from ram. And they take exactly the same cpu.

Attached you find 2 files
- test.tos runs the 7000 times dbra .x with look in icache frozen
- test2.tos runs the same 7000 times dbra fetched from memory (icache disabled)

they both give the same result; rastersplit midway of the screen. This leads me to believe that test.tos does not fuction as it should do

However, I will double check the systems number of cycles in a vbl to make sure its equivalent to 16 mhz.

Re: Low Performance Falcon

Posted: Tue Jul 09, 2019 10:38 pm
by exxos
If you use GB6, you can benchmark with caches disabled to check if any speed differences on any tests.