Run Blood in a window, open task manager and monitor task manager and your processes while you play.

This is the only program in which you experience such slowdowns?
Try to have a look at the hardware temperatures as well, sounds like thermal throttling 😅

DosFreak: Im not sure what to look at here.. theres nothing else eating memory.

alavro84: according to ATI Control Center the temperature is 67c

Oh, i just noticed when i start Blood using DosBox this message appears:

"14Mb memory used
LOW MEMORY WARNING: Blood requires 24MB of free memory
You may experience problems"

I should be able to adjust this in DosBox somehow, but how?

dosbox.conf, memsize=16

Or even 32 😀
I use dosbox with memsize=32 and Blood runs perfectly.

The default is 16.

I tried this but it didnt help 🙁
This is so frustrating..

Try dosbox 0.65 and set core=dynamic and cycles=auto there.

wd: When i tried that, Blood ran slow constantly.

That solves at least the temporary slowdowns 😉

Any idea when it happens? Does it vanish if you advance to the next level or something?

I have no idea. It just doesn't make any sense. It runs completly fine for a few minutes then the slowdown starts. They are not random, its like this:

3 minutes all fine
first lag 5 sec
runs fine 20 sec
second lag 5 sec
runs fine 20 sec
And so on so on...

It doesnt matter if i change to another level or if theres few/many objects on screen.
All of a sudden it just starts, for no reason.

DosFreak: Im not sure what to look at here.. theres nothing else eating memory.

We want to know about CPU usage not memory.

alavro84: according to ATI Control Center the temperature is 67c

That's the temperature of your video card?

Im rather new to DosBox. Are there any options/settings i should try out?
Except the memzize=32 that is.

Well DosBox uses about 40-50% CPU. When the slowdowns occur it drops down to about 30%.
The other processes uses 0% cpu, and when the slowdowns accur some of them raises to 1-2% cpu usage.

Do you have a CPU temperature monitor installed?
Is there any kind of temperature control program being used?

No such program installed. Only the ATI control center.

I actually think it has to do with the graphics card overheating. When playing current gen games i can hear the fan goin' like crazy, but when using DosBox its completely silent.. can this be the problem?

Maybe, but I don't think it's very probable. Dosbox, I think, does not stress the graphic card too heavily. Even my radeon 9600 pro could output anything under DosBox with any shaders that come with it in the resolutions I used it (1024*768, 1280*960), and my geforce 8600 gt can do 1920*1200 without virtually any performance loss (well, if I run SuperEagle shader 640*480 Blood start position framerate drops from 49 to 46-48 or something similar, the interesting thing is that it doesn't matter at all if I accidentally leave 8xQAA on 😕 ok, it's just 2 triangles, filling the screen once per frame 😀)
I can't say anything about GPU fans, I use passive cooled vcards 🤣

But DosBox uses the CPU much more intensively: on singhe core CPUs it should be 90-ish per cent running it at auto speed, and something like 40-50 on dual cores or HT enabled processors (it tries to use one of the cores to its fullest) (damnit, I forgot to have a look at its CPU usage on my shiny new Conroe-based rig, but on my AthlonXP it definitely used around 90%)

Those drops in the CPU usage might indicate that something runs there that shouldn't 😒 or it should, just it has an impact on DosBox performance. My single core AthlonXP usually ran uTorrent and boinc alongside DosBox transparently, but a virus scan can be more demanding.