[sdiy] Understanding upgrading SRAM in the 606?

[Trevor Page]

Hi,

To double the amount of memory in your 606, you could indeed install another two SRAMs, connect them to the same address and data lines. Your toggle switch would select which pair of SRAMs the chip select lines are routed to. Or (as I think Robin's mod does) replace the existing SRAMs with a larger capacity memory device, and use your new bank select switches to toggle the most significant address lines. 

I assume it's ok to flip between banks while the machine is running? I wonder if the CPU uses a small part of the memory for temporary variables etc. which it would 'lose' if you flipped to another bank, causing things to screw up? Best thing would be to try it. 

I've repaired memory -related faults in several TB303's and 606's. I'm not too sure about the TR606 here, but I often wondered if one of the three SRAMs inside the 303 is also used by the CPU for saving temporary variables, etc. associated with the currently edited pattern. If I recall correctly, the machine wouldn't save/recall any pattern at all if one particular SRAM was removed or non-functioning. But remove eiher of the other two devices, and certain pattern banks would still work. (I could be wrong). 

I've meant to learn exactly how these machines do save data to memory, if only I actually had some room to put the logic analyzer somewhere... (still stashed away at my parents')

Uh better go do some work now.

Trev

----- Original Message -----
From: "Rob B." <cyborgzero at home.com>
To: "Plutonique9" <Plutonique9 at symbiocom.com>, <synth-diy at node12b53.a2000.nl>
Sent: Wed, 2 May 2001 00:48:52 +0100 (GMT+01:00)
Subject: Re: [sdiy] Understanding upgrading SRAM in the 606?

> The piggybacking idea works, you just have to reroute the Chip
> select/read/write lines using a switch. I have thought about it, but haven't
> done it yet for my 606.
> 
> I assume the 303 is roughly the same.
> 
> Rob
> ----- Original Message -----
> From: "Plutonique9" <Plutonique9 at symbiocom.com>
> To: <synth-diy at node12b53.a2000.nl>
> Sent: Wednesday, May 02, 2001 3:32 AM
> Subject: [sdiy] Understanding upgrading SRAM in the 606?
> 
> 
> > Hey there,
> > I wrote about this a little while back, and someone sent me a link to
> > a schematic detailing an idea for a 32 bank 303 memory mod, not Robin
> > Whittle's though.
> >
> > I'm eager to learn on how the memory in these X0X's work, as both the
> > 606 and 808 desperately need more pattern data storage.
> > I don't want to go the big 32 bank mod yet, I'd even be happy with
> > just doubling the amount of space. I've tried reading up on SRAM, but
> > I can't find any information that is relevant to understanding how to
> > increase the banks in these X0X's, or really any instrument for that
> > manner.
> >
> > Is it possible to "piggy back" SRAM on top of the existing memory and
> > have some sought of toggle switch which chooses between which SRAM is
> > being used? When you push the bank number "I/II" on the 606, is this
> > just switching between the 2 sram chips onboard, or are they both
> > used in both mode "I" and "II".
> >
> > I'm sure it is not as hard as maybe I think, but if someone could
> > point me in the right direction in reading up on this subject, or if
> > the could clear up some of the "logic" behind how the memory works in
> > these machines, meaning what the how the Pins are used to select
> > different banks, etc. I'd be dig it extremely. It is a very confusing
> > topic to the new comer, much different from straight forward sound
> > modifications, but I feel this is only because of a lack of resources
> > on information on the subject.
> >
> > Anyways thank you, and could whoever sent me that 303 memory upgrade
> > schematic link, could you please forward it to me again.....:)
> >
> > Seeya
> >
> >
> > -- Plutonique9, Plutonique9 at symbiocom.com
> >
> > http://www.mp3.com/Plutonique9
> >
> >
> 




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