Emax

I'm not sure where you're located, but Jameco is the only place I've found these stateside without a minimum order.  I do not recall what speed the chips were in the EMAX upgrade, but here's the 1Mbit 80ns version.  I think they also carry a 70ns version for a few more cents.

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=42315

--- In emax@yahoogroups.com, tu@... wrote:
>
> 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
> > > > >
> > > >
> > > 
> > > 
> > > 
> > 
> > 
> > 
> >
>