Nord User Forum

Access Virus TI2.

The Virus and the Nords use the same type of DSP processor. The Stage 2 has six (see image earlier in this thread), the Virus has two (above and below the battery). The DSPs are exactly the same type and speed.



Edit: it is interesting to see how two companies who developed similar products (virtual-analog synth) around the same time came up with very different solutions.

Edit 2: Shoot! I just noticed the image I posted had the serial number of my Virus in it. Fixed, but I hope I was in time...

I'm curious : How do you read the speed ? On the quartz ? is it one of the 2 little oval chrome component under the "10" mark on the ruler ? On the processor spec sheet ?

From looking at the spec sheet a while ago, I know the last three digits are the clock speed in MHz.


Seems like these ones were made in week 9 of 2010.

This DSP has a PLL to synthesize a new clock signal, so it is probably running on a much slower external clock than 150 MHz, which is internally increased to the optimal 150 MHz.

I wonder if the DSPs are getting their clock directly from a crystal oscillator, since they two that are clearly visible are quite far away. Since the digital-to-analog conversion isn't done in this chip but in the DAC, a bit of clock jitter likely isn't much of an issue.

I wish I could clic many times on the thank button !

The 150 on that chip only represents the rated speed (i.e. what the chip manufacturer successfully tested the chip at). Sometimes chips will run faster than they were rated at for various reasons. For example, manufacturers have even been known to label faster chips as slower ones purely for stock reasons - for example they have too many faster ones but orders for the slower ones are outstripping demand. Another example is where a chip was first tested at a higher speed and it fails (may only be by a few Mhz), it may get dropped down the line and tested at a slower speed (which it passes easily).

The actual speed the chip is running at will be dictated by the clocks on the board. There will be some quartz oscillators there (the oval cans) - however these clocks may again be divided by logic. for example sending a 50Mhz clock through a flip-flop logic gate will output 2 x 25Mhz 'clocks'.

The easiest way to know for sure (without the luxury of a schematic) would be to probe the CLK input line on the chip with an oscilloscope.

Thanks for the fascinating pics. I'm humbled by the electronics!

Darren wrote:The actual speed the chip is running at will be dictated by the clocks on the board.

Yup.

Darren wrote:... however these clocks may again be divided by logic. for example sending a 50Mhz clock through a flip-flop logic gate will output 2 x 25Mhz 'clocks'.

They're not going to put a 150 MHz crystal on a board like that, let alone route that to multiple components (as some need to run in sync) - there are better ways to do that.

In this case the DSP contains a PLL and they can change the speed the DSP runs at from 1/16 x CLK-REF up to 4096/1 x CLK-REF (see datasheet or the bit about the PLL on this page: http://www.freescale.com/webapp/sps/sit ... e=DSP56367). A 16, 20 or 25 MHz clock seems fairly common.

One of my development boards has an NXP LPC4330 (ARM Cortex-M4) rated to run at up to 204 MHz - it uses a 12 MHz crystal and a PLL to do that. I also have some FPGA dev boards (such as the XuLA-200) and those can easily synthesize a 150-300 MHz clock from the 12 MHz oscillator on the circuit board; of course, comparing the (internal) clock speed of a CPU with that of an FPGA is not a very sensible thing to do.

I have a cheapy signal generator that uses an AD9851 DAC to generate signals - it runs at 180 MHz using its built-in 6X clock multiplier (doesn't state what type) and an external 30 MHz crystal.

Darren wrote:The easiest way to know for sure (without the luxury of a schematic) would be to probe the CLK input line on the chip with an oscilloscope.

In my experience the added capacitance (tens of pF) caused by standard passive probes (even at 10x attenuation) is often enough to stop the clock completely. I think you'd need an active probe to measure a crystal oscillator reliably (and those are rather expensive). I have a Rigol DS1052E scope (hacked to 1102E) and an old analog Philips one.

Anyway, it looks like I'm derailing this tread and turning it into a pissing contest. I'm certainly rapidly reaching the limits of my knowledge about stuff like this.

mjbrands wrote:

anotherscott wrote:previously, some people rigged up a key to get that low E working (and possibly the high notes as well), and now those mods don't work. So it would be interesting to know if they could be made to work just by manipulating these jumpers.

Okay, you've convinced me to give it a try. Seems like a legitimate enough reason (for me anyway).

I don't know when I'll actually get around to it, but here's to hoping I don't break it.

Any chance you ever got back to this?

Nah, I had to sell my NS2 a while ago. No more red lady for me, but at least I have a NL3 Rack now

No new synthporn MJ ?
We become addict you know !