Okay, a few solutions.
First of all, lower your draw distance and make the Visual FX quality to low (since the very high option makes the game ugly). After that try /fpslimit 90
Second, you could try the program "GTA Shrinker" which makes the game ugly, but it shrinks it for a higher FPS and a lower resolution. To install the program, just google it and/or
download from the link I provided you.
Then,
1. Unzip and double click on GTAShrinker.exe
2. Check the GTA:SA Directory box is correct
3. Click 'Shrink'
4. Wait till its done
5. Close GTAShrinker
6. Play SAMP at the chunky textures.
Hope it helps!
And if you want to restore it to normal, just open it and click restore (But first check the GTA SA directory).
:ps:
Not responsible for what happens to your GTA, but if there's a problem and I know the solution - I will help.