See the title. What can explain the major differences in performance between these cities? Ald'Ruhn is laggy and always crashes exterior-interior unless it's late at night. This is rare in Balmora and non-existent at Vivec.
It's a 8-year-old computer
It's a 8-year-old computer with 1GB Ram, Pentium4 and an ATI card that I'm too lazy to look up (should I?) I'm actually surprised that with the exception of Ald'Ruhn everything else runs relatively fine, though somewhat lagging next to candles.
Dunno about the ash storms,
Dunno about the ash storms, btw... The ashlander Urshilaku camp, the one with the wise woman who knows about the Nerevarine prophecies, is constantly beset by them, yet it rarely lags and never crashes.
Probably just all the stuff
Probably just all the stuff going on in Ald Ruhn (it's one of the biggest and most complex environments in Morroblivion with a large number of NPCs and things-going-on outside) combined with your PC and graphics card.
That's why Oblivion and Skyrim they put the cities in their own separate worldspaces with big gates around them -- easier on the PCs.
I can't run Open Cities (a mod that moves the cities to the same worldspace, like how they are in Morrowind/Morroblivion) for Skyrim or Oblivion without it bringing my computer to its knees, and it's a pretty high end machine (specs).
i also cannot go to ald'ruhn
i also cannot go to ald'ruhn without a ctd. i even ctd when i try to get to vivec temple. this never happened until i installed 0.9.0.1 and of course i can use the console to get those places but that is immersion breaking. Sorry I thought this was a skywind thread because i searched it on google and did not think to check.
How I 'fix' my morroblivion
How I 'fix' my morroblivion installation
I've found that every time a problem occurs, one or more mods have become corrupt or are just not compatible with morroblivion. Occasionally, Oblivion.exe becomes corrupted and requires an uninstall/install of Oblivion. A mesh or texture can be corrupt or missing and cause a ctd.
Usually caused by mods that don't play nice with each other or mods that don't play nice with Oblivion.
Sometimes you can 'fix' the error by just recompiling the offending mods.
Sometimes reinstalling the offending mods works.
Sometimes you need to make a change in the mod.
Sometimes you can adjust the Load Order of your mods to fix it.
Occasionally, you must just quit using the offending mod.
How do I check for corruption, you ask?
(see below)
Deactivate all mods except Oblivion.esm and Morrowind_ob.esm.
1) Load the game and check to see what happens.
2) Exit the game. If you got a ctd or other error or serious slowdown goto 2b)
2a) If the game did not crash, exit the game and goto 3)
2b) If the game crashed, exit the game and deactivate the most recent mod you activated. goto 3)
3) Activate one more of your mods.
4) goto 1)
Continue in this loop until you find and fix all offending mods. Either uninstall the offending mods or fix them as needed.
But I have 65535 mods. Is there an easier way? No. (However, You might try to get a Super Computer to see if the game will load and run on it) ..
Sometimes a creature or NPC gets stuck in a rock or a wall or underground. Causes slowdown. You can free it ingame if you can find it. Enter the Console ... activate the creature/npc ... type 'tcl'. Exit the console. Watch as the creature/npc scurries away. Enter the Console and Type 'tcl' again when the creature/npc is no longer stuck. Exit the console.
Sometimes you just need to activate the offending character and disable/enable it in the console. (makes the character go to its initial starting point)
If the game crashes with just morroblivion active, you should think about reinstalling morroblivion.
The procedures described here may or may not fix your individual problem. They might point you in the right direction, tho ...
Moderator/Admin .. if you see anything wrong, inaccurate, or an outright lie, please edit this post as necessary. Thanks.

Probably the dust storms that
Probably the dust storms that are causing it.
Specs on your machine?