[tremor] Minimum hardware requirements

[Jerry Durand]

At 08:21 PM 1/30/2003, you wrote:

>Most dsp's have builtin sram; the dram would be for buffering
>(or would you actually buy a meg or more of sram just for that?)

Depends on the DSP.  The cheapest DSPs don't support DRAM without external 
hardware.

<p>>For current Vorbis streams, 20 kwords or so of sram should be
>enough to do the decoding.  But you still need to buffer.

That sounds like a much better number.

<p>>>They don't make 10nS FLASH, so all us DSP guys have to copy the code to 
>>SRAM to run it.  So, we really DO care about the amount of memory.  In 
>>one of my typical designs, the SRAM draws 5X or more power than the DSP 
>>and costs more, too.
>
>Surely you don't keep all of the program in sram at all time?

Most of the programmers I work with do just that.  They consider the 
external SRAM the slow memory (1 or more wait states and ties up the 
external data bus), the fast memory is internal to the DSP (few nS access 
time in parallel to external data accesses).  They swap program segments 
into the internal RAM to execute.  Since most DRAM is now SDRAM, it takes 
even longer to set up a read, but at least the burst transfers are quicker.

A typical telecom design that I've done many times has 512KB of data and 
512KB of program SRAM external and no DRAM.  A high end board (like 
multiple video streams being compressed) has no external SRAM, but does 
have 32MB of SDRAM (and a DSP that costs over $100 in quantity).

<p>----------
Jerry Durand
Durand Interstellar, Inc.
219 Oak Wood Way
Los Gatos, California 95032-2523  USA
tel:  +1 408 356-3886
fax:  +1 408 356-4659
web:  www.interstellar.com

<p>--- >8 ----
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