emosun wrote:Well I'm not too worried about the drives speed at all as it's more of a cpu speed problem.
I'm not sure if you understand what DMA is then.
The thing is that without DMA, the CPU has to poll the controller for every single byte it receives. While the CPU is doing that, it cannot do anything else.
With a DMA controller, the CPU only has to start the transfer on the controller. The controller uses DMA to copy the data to memory in the background, and signals the CPU when it is done. In the meantime the CPU can do other stuff. That is why you can play a sample on the PC speaker *and* load new sample data on my IBM 5160.
emosun wrote:I think it's a good example of multitasking which the 486 isn't very good at unless the tasks are very light. It can play a terrible quality video with audio just fine , but not good quality video with audio.
Again, the rest of the hardware is also important for multitasking. If you see how well an Amiga can multitask with just a 7 MHz 68000 CPU... it's because all other chips can work with DMA alongside the CPU.
PCs have a very poor and inefficient design. The DMA controller on a PC is very weak anyway, and it only got worse when they stopped using DMA at all, and moved to CPU polling.
If your hardware can do things in the background, you get more mileage out of your CPU. A DMA-capable HDD controller could help, just as a video card with acceleration features.
One example I can think about is my Pentium 133. Originally I had an S3 Trio64 card, which allowed me to play VideoCD in 640x480 in 16-bit colour. I couldn't do higher resolutions though, because the CPU had to scale the video up, and this took too much bandwidth.
When I upgraded the Trio64 to a Matrox Mystique, I got hardware-accelerated scaling, so it now played in 1024x768 just as well as in 640x480 before. The scaling was basically 'free' on the CPU now.
Likewise, if you could use a better HDD controller, which saves you some CPU cycles, these cycles could be applied where it matters: the actual decoding of video and audio.