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Old 07 January 2010, 02:21   #117
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Originally Posted by hit View Post
noone with an idea, what could fit in the Xena(s)? *gosh*
what about [ Show youtube player ] emulation ?
since one of the amiga custom chips was inclusing the floppy-controller, is it possible to have one in these Xena(s) - using the xorro-slot to have a floppy connected?

if i got the concept of the Xcore somehow correct, its like an FPGA - but here you have the advantage, its been integrated in a whole system - no need for special developer boards or the like, just an interface card, for what you want connect to it.
doesnt sounds that bad.
It's not an FPGA. It's a sidekick processor that is designed to deliver low-latency responses to external inputs. Since it has 8 threads, it can process interrupts (such as those used in device drivers) with minimal latency. This means it will run existing hardware faster than if the main processor had to be interrupted all of the time.

In case you didn't know, hardware interrupts are expensive on anything newer than a flat 68000 due to pipeline stalls and cache dumping. The newer the processor, the more expensive the interrupts.

--The Long Explanation--
Interrupts are, to make a long story short, for the processor to finish up what it was doing and store all of its registers (temporary storage in the CPU) to memory, do something else for a while (called an interrupt service routine), pick up the contents from its registers from memory again and go back to doing what it was doing before.

The way the Xena chip works is that it keeps the interrupt service routine in its own local store memory (memory inside the Xena chip) and maintains 8 of its own register sets called threads. This means that when something that the Xena chip is controlling needs to do what would normally interrupt the processor, Xena takes care of it herself.

--The Short Illustration--
Xena is like a secretary that takes phone calls and answers mail to make sure the boss doesn't get interrupted unless he has to be.

--How it Applies to Emulation--
A lot of what emulation is is translating memory and port accesses to look like other memory and port accesses on another system. Since I/O chips on the emulated platform are different from the original, Xena can do emulation to imitate the chips for up to 8 things at a time. This frees up the main processor to do faster JIT compilation to actually run the program.

Last edited by Samurai_Crow; 07 January 2010 at 02:23. Reason: Bolded headings for emphesis.
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