Gp2xpectrum 1.4b2


Metalbrain

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Hi all!

Here's another version of the ZX Spectrum emulator:
http://www.speccy.org/metalbrain/GP2Xpectrum1.4b2.zip

and here too (once updated):
http://www.gp2x.de/cgi-bin/cfiles.cgi?0,0,0,0,5,1786

What's new:
- CPU speed increase to 125/170 wasn't enough, and many games performed slower than they should, so I had to put the default speed up to 150/185
- Speed can be changed from the menu using VOL+/-, and can be saved for each individual game together with their keyboard profile
- Fixed memory contention for +2A/+3 models (Overscan now works)
- Changed the way to avoid the MMU hack problems, using Notaz's flush cache function instead of a screen buffer.
- Fixed a bug in L & R buttons assignation from .key file

Since CPU speed increase has been quite high, I'll probably leave precise contended memory emulation as optional for 1.4final version, as I did with No Frameskip vs Frameskip 1
 
Thanks for this, I'll test it in a moment!

However; what sort of core are you using for this? I didn't think a Z80 took that much to emulate. Not a complaint, just an observation and curiosity :)

It's great to play these again. Also: the snapshots are tiny, so a bonus for flash capacity! :D

But... "ROM LIST"....?
 
Retroid said:
However; what sort of core are you using for this? I didn't think a Z80 took that much to emulate.
You'd be surprised. If you're a windows user, and you want as much accuracy as is really warranted for playing games and multicolour demos then you'd be needing around 300mhz, maybe more - that's with a core written in C. I've seen an insanely accurate emulator written in pure x86, which requires only 200mhz. If you wanted the ultimate in accuracy for a Speccy emulator, you'll need more than 1ghz to get all the graphical tricks running flawlessly.

For a handheld, I'd not expect you to need much accuracy - after all, you're hardly going to be developing TRDOS demos on it, just playing games. I personally wouldn't expect to be running demos on it - the desktop PC is much better suited to the non-interactive stuff. This being the case, you could get a reasonable core going in less than 100mhz (early PC emulators managed it in 33mhz and sometimes less, but the compatibility was shockingly bad).

GP2xSpectrum emulates more than just the bog standard 48k/128k models though, and allows more file formats than just snaps, and also emulates the undocumented flags and instructions so will require a fair amount of CPU power.

D.
 
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Retroid said:
Thanks for this, I'll test it in a moment!

However; what sort of core are you using for this? I didn't think a Z80 took that much to emulate. Not a complaint, just an observation and curiosity :)
A custom C one, that must take care of very precise timings. Maybe I'll try to replace it with a modified DrZ80 in the future.
 
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I know it's very easy (heh, right) to get Z80 emulation up and running but exceedingly difficult to get all the timings right in a machine like the Spectrum.

Bear in mind that I was emulating the 48K machines on my 50Mhz 68030-accelerated Amiga 1200 with no hassle, yet when 128K was tried it was a whole new ballgame.

Just curiosity :)
 
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