[sdiy] SRAM Memory Upgrade (Old Sampler) ???

[Ingo Debus]

Am 27.08.2005 um 21:30 schrieb ::Phuture:::

> Right now, the sampler uses a single 32k x 8-bit 28-pin DIP CMOS  
> SRAM. This, i believe, was the largest possible size in a 28-pin  
> format. Now, hopefully, I'd like to install a 32-pin SRAM in it's  
> place, which is organized as 512k x 8-bit (16 times the original  
> size). Aside from the top 2-pins on both sides of the 32-pin IC,  
> the rest of the pins line up with the original 28-pin SRAM.
>
> The difference between the two chips, besides the VCC being on a  
> different pin, is that there is an additional (4) address  
> lines....... All other pins are compatible with the 28-pin version.
>
> Now, I'm no expert on how memory works.....but from my research it  
> seems like adding 4 spdt switches to control the highest 4 address  
> lines would give me (binary) access to switch between the 16 banks.  
> Is this correct?
>
> Aside from the additional banks, the newer SRAM would give data  
> retention of 10+ years because of an inbuilt lithium battery in the  
> IC.
>

I agree to what others already said, this surely will work. I did a  
similar thing with my DX7 long long ago (replacing a 2k SRAM with an  
8k one).

Does the unmodified sampler already keep its memory contents during  
power off? If not, it will probably overwrite the memory after power  
up, or at least the pointers to the samples or whatever. If the RAM  
isn't battery powered, the designers sure had done something to  
prevent  the sampler from generating ugly noises due to random memory  
contents.
OTOH, if the original design is already battery backed up, you'll  
probably be fine with RAMs without an internal battery. Perhaps you  
have to replace the original battery too because the sampler is so old.

Ingo