code in ram?

[CrazyBoss]

From A hardware view it should be quicker to read code from ram, instead of a rom - any one tried it ? Will the code run a bit quicker if moved to ram and executed in Ram ?

 

Maybe this subject only fits assembler programmers, guess its not so easy for c programmers to control code and move it around.

 

I remember the MSX turbo-r had a mode where the roms was moved to ram, to let it execute quick enought for the R800 processor (Risc compatible z80)

 

 

 

[PkK]

From A hardware view it should be quicker to read code from ram, instead of a rom […]

 

No. Why shoud it be?

 

Philipp

[+Gemintronic]

 

No. Why shoud it be?

 

Philipp

 

On some systems it does matter. Maybe it's an SNES generation thing. I remember hearing that the CPU would operate at different speeds depending on the ROM used (SNES) . I take it access time is the same on the Coleco?

[PkK]

Yes. Any memory access takes the same time. You can look up the number of cycles for an instructon in the Z80 manual, and divide by the frequency to get the exact time.

 

Philipp

[+nanochess]

From A hardware view it should be quicker to read code from ram, instead of a rom - any one tried it ? Will the code run a bit quicker if moved to ram and executed in Ram ?

 

Maybe this subject only fits assembler programmers, guess its not so easy for c programmers to control code and move it around.

 

I remember the MSX turbo-r had a mode where the roms was moved to ram, to let it execute quick enought for the R800 processor (Risc compatible z80)

 

 

 

 

As far as I know, the Colecovision runs the code at same speed, doesn't matter if it's in RAM or ROM.

[artrag]

On msx turbo-R the built-in RAM is of a special faster kind, suitable for the R800 (CPU compatible at logical level with the z80).

Used in z80 mode there is no speed difference. The same on msx1 and msx2 (based on z80).

I do not see reasons to have speed gains on coleco by using the ram for code.

[Keatah]

It just depends on the chips' speed and how the memory is wired up. RAM or ROM makes no difference.

[hardhat]

On ColecoVision, RAM and ROM run with no wait states, so are the same speed.

[BrianBeuken]

The only real advantage, is running in RAM allows you to use self modifying code which was useful in the early Z80 days on computers to save variable space and make some routines a little faster (direct load of a register is faster than a memory load) several clock cycles can be saved in loops, but with the CV having such a small amount of RAM and its video being tied to the TI chips access clock, there's not a lot to be gained from these kind of code gymnastics. But am sure someone will find a good reason to do it.