Has anyone experienced jerky or inconsistent display speeds. My setup will play smoothly then suddenly and unpredictably speed up. It then goes back to normal speed.
Pretty much unplayable this way.

I've had lag (but not too bad) as I've approached high detailed areas like cities, could that be the issue?

Not quite. It does seem to occur near high detail areas, but the problem is that is that the game will suddenly increase speed and become unplayable. It will go back to normal speed after a second or two.
This game prompted me to acquire EE2: Desert Operations. That game plays just fine on the same hardware. Hey GOG, see if you can add EE2 to your library!

I am having the same problem with the graphics where it can jerk about and make the game unplayable, thought it might be the joypad playing up so i uninstalled it and it made no difference, it can throw the helipocter 2000ft into the air or into the ground in a split second.
Also the game randomly crashes/lock up when starting up and i have to restart the system.
Could this be a processor problem as i also tried it on my older spare machine and it has the same problem, both are dual core processors (amd & intel) and both are using nvidia cards.
It seems a lot of older games (direct x 6.1 & 7) really seem to struggle on modern machines even though the cpu & gpu aren't being strained. (Freespace 1 & 2 also lag quite bad at times). Anyone know if this directx related or an Nvidia driver problem ? (i hear ATI cards have much better support for the older drivers).

I remember from some other game that had the same problem that you could disable in the process manager the second core. Somewhere with right-click, properties, etc you could tell the process to only use one core. This solved the problem.
I have the same problem, but as soon as I try to open the process manager, apache havoc quits :(

I posted this in another thread about framerates... Hope this helps...
So I noticed when I would be flying around cities it would seem to smooth out, and when out in the open I would get crazy framerates, actually it seemed to go into overspeed and I would end up in timbuktu or whererver... I opened up the nvidia control panels and turned on all of the antialiasing and any setting that would use up some processor juice and the game ran a lot smoother. I will play around with it some more and post what I find.

A lot of games now are having problems with new Nvidia drivers, in that they weren't tested with those drivers at tghe time (natch). Even newer games are having the same problem, eg. Empire Total War.

There is a possibility that you're running into a timing-problem due to a dual-core issue.
If you have a processor with more than one core, try disabeling all but one after starting
the game. (via the process manager).

Launching task manager during a gaming session to set CPU affinity can really bring many old games down (and not to mention the hassle of doing it every time). For an automated and more permanent solution, grab RunFirst from http://www.activeplus.com/us/freeware/runfirst/ and create/modify the target game shortcut to something like this: C:\windows\bin\runfirst.exe D:\Games\GoG\EECH\eech.exe.
Hope it helps.

I tried using that suggested shortcut modified for where I'd put run first, but it simply did nothing, and when I try using Set Affinity, the main menu of Apache vs Havoc stops responding. Any other ways of getting this to work?

See my two seperate threads to solve this and resolution problems!

I was having this issue and tried to resolve it few years back but nothing helped.

I've tried running the game on one CPU (with imagecfg.exe) along with CPUgrabber and CPU killer (running on the same core as the game). It helped in some ways but there was still occurences when the game became choppy with inconsistent time speed in game. BTW I always try to resolve any issues without having to use any CPU bogging software as it stresses the CPU which isn't an elegant solution.

I've tried enabling the vertical sync to no avail.

I've also tried decreasing the multiplier on my motherboard for the CPU from stock 15x to 5x making my CPU basically a 1GHz running chip (It's running on 200MHz FSB -> 5x200MHz=1000MHz), but that also didn't helped. So I finally gave up.

I recently got interest to play the vanilla game again and tried simple solution, I don't know why I didn't tried that earlier. Basically what I have done was to limit the FPS for the game. That made the game run smoothly, without any inconsistance in speed! Just like the old times. Unfortunately, the nVidia software doesn't provide any means to do that so I used nVidia inspector to limit the FPS to 30 and forced the vertical sync (see attached file).

I've tried that on Win XP SP3 with GTS450, but will have to try that on my other, less ancient PC with Radeon HD 6850 and Win7.

I hope this helps anyone who wants to try the game in it's vanilla form.

EDIT: It appears that after running the game once more the problem have returned :(
I've uninstalled the GOG version, removed the nVidia Inspevtor tweaks (FPS limit and vsync), installed retail version from CD and run it (ver. 1.0c) and the speed fluctuation issue is there, but after installing the official patch 1.1e it seems to be gone. Without any tweaks the game works out of the box. At least for now... I have flown few missions in the Campaign. Restarted the game once more, loaded the saved campaign and no speed issues encountered so far

If I wont encounter the issue again with 'retail version + 1.1e patch' it will seem that the GOG's version is broken..

EDIT 2: After running the retail version of the game again today the issue is back! So it appears the GOG's version is the same as 1.1E retail version after all. Too bad it doesn't work right. But the odd thing is one time it runs perfectly and the other it's not.