Just-for-fun Emulator in Java

Kananga · Post by **Kananga** » Mon Mar 08, 2010 2:23 pm

After finally figuring out how to read the instructions for registration to this forum I am now able to announce my current toy project:
A Vic-20 emulator in Java.

I wrote one in C++ once and it was reasonably fast, but lost the source code. This one was more fun to write and I learned a lot about Java, but it is dead slow.
You will need at least a quad-core at 2.5GHz to run it at reasonable speed.
It is also not ready for using without knowledge of the VIC-20 and in no way competing with very good emulators like VICE.

However, I enjoyed reviving my memory of the good old days in Java code and want to share the fun. Please feel free to have a look.

http://code.google.com/p/vic20emu

Kweepa · Post by **Kweepa** » Mon Mar 08, 2010 4:48 pm

Cool!
We now have emulators coming out our ears!

Did you see this?
http://www.kweepa.com/step/vic20/jarvic.html
(No debugger)

Steve

EDIT:
Had a poke around the googlecode page. Very interesting! It looks very well structured. And the screenshot is intriguing.

Kananga · Post by **Kananga** » Tue Mar 09, 2010 1:34 am

Nice emulator. And fast too!
I like the TV image and the keyboard-style menu.

I was not aware of Jac64 or forgot about it. Perhaps I can learn from the source how to write a fast emulator in Java.

Kweepa · Post by **Kweepa** » Tue Mar 09, 2010 10:17 am

Kananga wrote:I was not aware of Jac64 or forgot about it. Perhaps I can learn from the source how to write a fast emulator in Java.

The basic idea (this is how most emulators get their speed in my experience) is to have a large switch statement to handle the CPU emulation.

For the "GPU", caching and lookup tables.

Kananga · Post by **Kananga** » Tue Mar 09, 2010 1:08 pm

Kweepa wrote: The basic idea (this is how most emulators get their speed in my experience) is to have a large switch statement to handle the CPU emulation.

The emulator I wrote in C once used a jumptable with 256 entries, so the switch is not the fastest option, at least without a good compiler. CPU emulation speed is not my main problem, but I suspect the clock emulation/synchronization to be a bottle-neck. VIC emulation is the slowest.

Kweepa wrote:For the "GPU", caching and lookup tables.

Part of the problem is my poor knowledge of graphics in Java. I will have a look at the "GPU" code of Jac64...

rhurst · Post by **rhurst** » Tue Mar 09, 2010 2:00 pm

Kweepa wrote:We now have emulators coming out our ears!

Yeah, and propellers spinning on the top of both your heads, too!

Kananga · Post by **Kananga** » Wed Mar 10, 2010 3:15 am

rhurst wrote:
Kweepa wrote:We now have emulators coming out our ears!
Yeah, and propellers spinning on the top of both your heads, too!

Propellerheads, wohoo! Now it's three