> ] > runs a program from internal RAM, it runs approximately 6 times as fast as
> ] > the Z80. However, it the R800 runs the same program from external RAM, it
is
> ] > only approximately 2 times as fast as the Z80.
> ]
> ] So a 1MB or 4MB external memory mapper, will not be very useful for a turboR
with
> ] GEM?
> Depends on how GEM has been written. If for example the code remains in the
> internal RAM while the data remains in the external RAM, you loose less
> performance. Most memory accesses are for fetching instructions, so the
> instruction fetch would still be fast. In such case, you would only get
> slow-downs for the data fetch.
>
> But since I do not know how GEM has been written, I can not answer this
> question for you.
Since Patriek hasn't answered on this one...
Internal RAM will always be faster. Use it if possible.
However 4MB external RAM will enable you to run more games with the latest
version with dynamic recompilation core, and the increase in speed is greater
than the loss because of RAM wait timings (unless external RAM on a turboR is
REALLY slow)... With 512kB internal RAM (tR GT) you can run roms up to 128kB
using the dynarec core.
Maybe some parts of the emulation core can be put in the internal RAM while the
game and some other parts (to avoid switching) are in external RAM... I believe
the code in page 3 was never switched to game rom... In that case, maybe it's a
good idea to locate as much often-accessed routines in that area as possible.
Patriek???
~Grauw
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