[sdiy] Digital delay memory

[Jay Schwichtenberg]

Now days there are large SRAM parts out there. While they still aren't as
dense as the DRAM parts they are probably big enough for audio work. If you
have a DRAM interface in the chips that should be handled in the background.
If not you can do it but as said it takes some work.

I use to do sound cards in the mid-90's. Normally the cards would run with a
-85 to -90 db noise floor (24 bit, 44.1 kHz Cirrus ADCs/DACs). I did an
experiment once when we were measuring things on an Audio Precision where I
froze the DACs while we were measuring the noise floor. It dropped to
between -100 and -105 db.

Jay S.

-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of
Eric Brombaugh
Sent: Wednesday, April 27, 2016 11:07 AM
To: Richie Burnett; synth-diy DIY
Subject: Re: [sdiy] Digital delay memory

On 04/27/2016 10:57 AM, Richie Burnett wrote:
>
> Although one is supposed to refresh every location of DRAM at least
> every 16ms, I was once amazed to find intelligible audio playing out of
> the chips after I'd hit a breakpoint in the debugger and the refresh had
> be stopped for a couple of minutes!

That's true - DRAM data becomes unreliable if not refreshed but it 
certainly doesn't decay away to nothing. I remember "the good old days" 
when cycling power on a DRAM-based video card would still leave 
recognizable data visible on power-up.

The rate of data corruption is related to temperature - there are known 
computer security issues where hackers load up a machine's memory with 
secrets, cool the RAM with freeze-spray and then cut the power. 
Rebooting with a compromised OS then allows dumping the contents of the 
RAM for analysis without the victim OS and applications being able to 
detect the intrusion.

Eric

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