Emax

Which processor are you referring to? The sample RAM is connected to the G chip and not the main 32CG16 CPU, which incidentally runs at 20MHz. 
The G chip is not documented in the Emax II service manual but I think it is likely it runs with a fixed DRAM bus cycle time in order to process the 
32 voices and pass the channel data to the H chip at the fixed internal 39k sampling rate.

The 44256 DRAMs are asynchronous DRAMs and are not accessed the same way as the synchronous DRAMs (SDRAM/DDR) you are familiar with on 
your PC. The speed grading on the 44256 DRAMs indicates the shortest access time that is guaranteed for either row or column access, often the 
random read/write access time will be a little slower. The chips of a given speed rating may respond faster but it is not guaranteed and may or may 
not work reliably at the high speed with elevated temperature etc. For SDRAM the speed is rated to the maximum speed that data can be 
sequentially clocked to or from the memory but random read or write access is actually much slower.

Therefore you should aim to use 44256 DRAMs with a speed equal to or greater than the timing on your existing sample RAM chips. You might get 
away with using chips that have a slower access time but you run the risk of corruption of the data in the sample RAM :P

/Tristan

On Wed, Dec 16th, 2009 at 6:44 PM, thenewyorkcowboy <thenewyorkcowboy@...> wrote:

> That is good to know!  Since the processor is only 6Mhz there may not
> be that much difference of a 10ns spread.  I wouldn't try any 120ns
> chips though, as that is nearly double.
> 
> I know from PC experience that 66Mhz are 10ns, and the 100Mhz chips
> are 8ns, a difference of only 2ns to be able to be stable and pushed
> at 100mhz but we are talking about large quantities of memory
> compared to 8mb of an Emax running at a paltry 6Mhz.  I could almost
> always clock a 66Mhz chip up to 83Mhz.
> 
> Good luck!  I learned something new too!
> 
> --- In emax@yahoogroups.com, "dwv1957" <dwv1957@...> wrote:
> >
> > I have chips from 4 different manufacturers, and 3 different
> speeds, with no problems, just be aware that the system will run at
> whatever speed the slowest chips are.
> > 
> > Dave
> > 
> > --- In emax@yahoogroups.com, Louis van Dompselaar <louis@> wrote:
> > >
> > > Does anyone have any experience with maxing out the EMAX II with
> DRAM
> > > from different manufacturers?  I have a hard time finding 32
> identical 44256, but
> > > I can get a batch of 40 different ones (which only includes a
> maximum
> > > of 13 from a single manufacturer).
> > > 
> > > I considering getting those, unless someone already has bad
> experiences
> > > with mixing DRAM chips.
> > > 
> > > Louis
> > >
> >
> 
> 
>