Ram Tweaks?

[Si7777]

Hello - Just got my new GP2X a couple of days ago. I'm very impressed with the machine as it stands - just ordered a lot of extras (cradle, AC adapter, SD card etc.).

However, it seems that I may be one of the "Unfortunate" ones who got a low overclocking unit. I can only stably O/C the main CPU to 245 / 250 (depending on what I'm running - Quake will only work at 242 or less!). Therefore, to get the most out of my unit, it looks like I have to turn to tweaking the RAM.

This is where I'm getting a little stuck - I've used the CPU - LCD - RAM Tweaker program to adjust my timings with variable success. Then, after reading up on alternatives, I added GMenu2X to my SD card to enable O/Cing per application. Part of this program contains an option to "Tweak RAM Timings."

So, my question is, not "What does RAM tweaking do" but "What are these tweaks exactly and how tight does this push the GP2X?" As I can't push my CPU too far (Picodrive does some funny things if pushed passed 237 MHz when the second CPU is enabled for audio), my other option is to optimise the RAM settings.

 

[god_at_hell]

RAM has latencies ... that's for instance the time that passes when a column of data in the memory is accessed. This means a smaller time interval results in more performance ... but if this interval is to small, there can be an error and the ram becomes instable. Memory is mass fabricated and so the timings are relative slow to get a stable chip, even if this chip is not soo good. This means you can use stricter timings in most cases and gain some performance.

This doesn't do anything if your program is very small and doesn't use the ram very much ... but programs like eg. gngeo perform quite a bit better with stricter timings.

 

[Blah]

Some programs (for example Picodrive and Gmenu2X) have an option to enable some RAM settings tweaks designed by Craigix. These settings are designed so that they should work on any GP2X, however they are disabled by default just in case there happens to be one that isn't up to spec.

However, your GP2X's RAM may be able to handle stricter settings. Download the utility called "cpu_speed". It is what you need to experiment with RAM and CPU settings. The included readme should shed some light on how to do this, and what to try.

Do not worry about damaging your GP2X. The worst possible thing that could happen is a reboot.

And if you need further help (like if you can't figure out how to make the scripts or something), don't hesitate to post here. I will get off my lazy arse and tell you what you need to know. ...maybe.

 

[Si7777]

Thanks for the replies and help. I've been experimenting with CPU LCD RAM Tweaker (nice program god_at_hell BTW, especially like the BIOS style, easy to navigate). I've managed to improve performance quite a bit through improving the timings - an example is in MAME 4.7 with Final Fight (US) - before (no RAM tweaks, 245 MHz) I got an average of ~25 fps; with RAM tweaks (still at 245 MHz) the average I get is ~37 fps, a significant improvement. I'm yet to test in GnGeo, but I expect an increase will also be apparent after optimising the RAM timings, as with other games / apps / emus.