Emax

I mean use DRAMs with a speed rated equal to or faster than what you have already. 

/Tristan

On Wed, Dec 16th, 2009 at 9:01 PM, tu@... wrote:

> 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
> > > >
> > >
> > 
> > 
> > 
> 
> 
> 
>