In my experience with Classics, Deneb, and DMA vs. PIO, you really don't gain much by using the Deneb in DMA mode. When you are driving these devices so fast on the Classic systems your CPU is still being used quite a bit and DMA vs. PIO is about a 5% difference in CPU usage.
It's a general lack of CPU horse power and other sub-system slowness (like Zorro III) that are more of an issue. My recent networking tests using a Deneb in DMA mode (OS 3.9) and PIO mode in AmigaOS 4.1 Classic showed only about a 5% drop in CPU usage in DMA mode.
erm... amiga networking is probably the worst test you could do to compare DMA vs non-DMA drivers because SANA-II is totally cpu driven. If you want to perform a decent test use an external USB2.0 hard disk, at least the cpu won't have to copy everything everytime.
-edit- moreover, comparing the performance of drivers with the goal of getting some information about DMA vs non-DMA performance is nonsense if you are using OSes with different cpu architecture. Since most people use OS3.x and not OS4.x the interesting test would be comparing DMA vs non-DMA in the same conditions.
If you are going to perform benchmarks of DMA vs non-DMA drivers you should:
1.- Try to use the same conditions:*Same OS version, same cpu, same HD.
2.- You should use something meaningful that uses DMA. Networking doesn't. Use an USB2.0 hard disk for example.
