The dreamcast has a Hitachi SH-4 200mhz CPU, and a SGI GPU probably running at 100mhz, and capable of about 1.5M polygons per second, but I don't think the GPU is used in Bleemcast. It also only has 16MB of 100mhz RAM. The GP2X can run at least 240Mhz, is dualcore, and has more RAM. The beta bleemcast runs any PSX game on dreamcast, and frequently it runs them at full speed or faster.

The Dreamcast has a 3D Chip / FPU.

The GP2x doesn't.

I'm pretty sure you'd HAVE to use the 3D chip to get any speed. And also, to my knowledge the SH4s are pretty beefy processors. WITH floating point - that's probably why they were used as expansion chips, I'd think. Virtua Racing, was it? And Bleemcast was written in pure SH4 assembly direct to the hardware of the Dreamcast. And with a dev kit created solely by hand by the creators in Assembler. With no OS. Oh, and they also had a playstation emulator they created themselves on the PC to port, which they wrote from scratch and knew inside out. As far as I know.

Khatoblepas pretty much got it spot on.

and for bleem team to port it was probably easy because of the fact that dreamcast ran a very early version of windows CE which is now windows mobile

there's know way they used windows ce for bleem.
Win CE has really bad speed and performance. Bleem was written in asm.

that's probably true, dc games i have that use windows ce are incredibly poor in performance such as rainbow 6

Extremely so; one of my favorite CPU architectures (along with ARM and 680x0 ). The SH-4 has an extremely fast 128-bit floating point unit, and I'm positive the 3D hardware was used. Software rendering is slow even on very modern desktop processors. The raw 3D hardware is probably why the performance is so stellar-- the PSX's CPU was an integer-only MIPS unit similar to the one in the PSP, albeit a couple generations back and at a massively lower clockrate. It's also distinctly possible SH-4s have a higher IPC level than ARM920Ts (Instructions per Cycle, actual raw performance per clock tick / Hz).