exxos's Atari, Amiga & retro forum

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.

Have you checked the CPU clock.. Sounds like your falcon is stuck in 8mhz.

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?

You could try SI.CPX I think I used it on the Falcon to test GB6.. but it was a couple years ago now...


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.

Nembench report:

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.

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.

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.

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.

If you use GB6, you can benchmark with caches disabled to check if any speed differences on any tests.