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NeXT DSP Memory Expansion Module
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balrog



Joined: 20 Jul 2010
Posts: 23

PostPosted: Thu Aug 12, 2010 10:44 am    Post subject: Reply with quote

I did some more research and it seems that the board thickness may be an issue. A 4-layer board from most fab houses would be about 1.2mm thicker than the original. A 2-layer design would probably be feasible, and flatpack SMT ICs may make it easier.

EDIT:

Does anyone have potentially useful information? I think pentium said something about this... any such information may be useful.
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pentium



Joined: 23 Jun 2006
Posts: 1148
Location: Kamloops, BC

PostPosted: Sun Aug 15, 2010 9:59 am    Post subject: Reply with quote

Rolling Eyes
There is like, five pages of content and links. Go back and read them and you will find all you need.
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-NeXT 68040 Cube with NS 3.3 and 64Mb ram
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balrog



Joined: 20 Jul 2010
Posts: 23

PostPosted: Sun Aug 15, 2010 10:25 am    Post subject: Reply with quote

pentium wrote:
Rolling Eyes
There is like, five pages of content and links. Go back and read them and you will find all you need.


Ohh I've read all that. I mean, any additional information that isn't here. Smile

I'm sure I can do without it, though.
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pentium



Joined: 23 Jun 2006
Posts: 1148
Location: Kamloops, BC

PostPosted: Wed Aug 18, 2010 9:26 pm    Post subject: Reply with quote

This is all we got.
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NeXTnewbe



Joined: 27 Oct 2006
Posts: 276
Location: UK

PostPosted: Wed Oct 06, 2010 6:36 am    Post subject: Reply with quote

Hi

any news or updates about this topic
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sdinet



Joined: 25 Jun 2008
Posts: 184

PostPosted: Fri Oct 08, 2010 7:10 am    Post subject: Reply with quote

If someone is willing to donate a DSP simm, I can work with grant stokely (make of the altair and kenbak reproduction kits) to build a lot of these simms. It may cost a bit, so we would all need to split the costs.

Too bad I sold the only DSP simm I had 6 months ago =(
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NeXTsociety



Joined: 29 Nov 2007
Posts: 453
Location: Grass Valley, CA.

PostPosted: Fri Oct 08, 2010 9:14 am    Post subject: Reply with quote

This may be a dumb question but what would this device do for us? Sounds like it offers more memory to DSP functions but is the DSP that heavily used where we would see speed improvements someplace?

Just trying to understand what an upgrade like this would do for us commoners. Cool

tj
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pentium



Joined: 23 Jun 2006
Posts: 1148
Location: Kamloops, BC

PostPosted: Sun Oct 10, 2010 11:14 am    Post subject: Reply with quote

sdinet wrote:
If someone is willing to donate a DSP simm, I can work with grant stokely (make of the altair and kenbak reproduction kits) to build a lot of these simms. It may cost a bit, so we would all need to split the costs.

Too bad I sold the only DSP simm I had 6 months ago =(


We have all the reference material we need to reproduse the SIMM here in the thread. That is about sa good as we are going to get when it comes to getting hold of a real SIMM.

We really don't know what it will do. Even I think it's really just a fun and novelty item.
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cubist



Joined: 20 Sep 2007
Posts: 246
Location: Cambridge, MA

PostPosted: Sun Oct 10, 2010 3:41 pm    Post subject: essential question Reply with quote

NeXTsociety wrote:
This may be a dumb question but what would this device do for us?


That's really the most important question. My recollection is that only the CCRMA MusicKit and some other custom stuff (perhaps IRCAM) will use the added memory. I may be wrong but that's the story I know.
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SlateBlue



Joined: 23 Aug 2015
Posts: 75

PostPosted: Mon Feb 06, 2017 2:24 pm    Post subject: Reply with quote

I'm bumping this thread thinking I may be able to help. In a lot of NeXT hardware and software I recently acquired was a DSP expansion kit that contained the module itself; it appears to have never been used.
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pentium



Joined: 23 Jun 2006
Posts: 1148
Location: Kamloops, BC

PostPosted: Tue Feb 07, 2017 6:23 pm    Post subject: Reply with quote

You able to get an xray of the SIMM? Not much can be done for reverse engineering at this point without figuring out what that middle layer is doing.

Well okay, we CAN do extra homework and figure out where everything went but the xrays would make it much easier.
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SlateBlue



Joined: 23 Aug 2015
Posts: 75

PostPosted: Tue Feb 07, 2017 7:25 pm    Post subject: Reply with quote

Hmmm... my immediate answer is no. But, maybe I can figure something out.
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SlateBlue



Joined: 23 Aug 2015
Posts: 75

PostPosted: Sat Apr 15, 2017 4:50 pm    Post subject: Reply with quote

To update: I do not have the resources to get the module x-rayed. The next best thing I can think of is to use a multimeter to trace continuity, then document. This is time consuming, of course, but it's the best I can do at this point. Seeing as how this thread was started 8 years ago, I'm wondering if interest has diminished or if it was simply unable to progress any further. One question: if the community has the schematics for the 576k module, why not reproduce it?
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SlateBlue



Joined: 23 Aug 2015
Posts: 75

PostPosted: Tue Apr 18, 2017 6:56 pm    Post subject: Reply with quote

Hello NeXT community. bobo68 and I have put together a spreadsheet in an attempt to reverse engineer the NeXT 96k DSP SIMM. bobo68 has been immensely helpful in organizing the spreadsheet and documenting information. I just manned the multi-meter.

The spreadsheet is here: https://docs.google.com/spreadsheets/d/1IEQZNNyqNDBm2rji7DHeYrpfK_TktUw3WzUsdI8wsJM/edit?usp=sharing

We're hoping some of you can make sense of the information we've gathered. We have a few unanswered questions, and I personally lack the knowledge to answer them. We also hope this information is helpful in visualizing the internal board layers.

Here is a brief summary of our findings:
    Regarding the 74F158 multiplexer, it seems not all inputs/outputs are used.
    SIMM pin 42 (DSP Data Select) does not appear to connect to any component on the module. Why?
    SIMM pin 64 does not appear to be used.
    There seems to be common GND and Vcc planes. All GND pins connect. All Vcc pins connect.
    Address pins of all SRAMs connect in parallel to each other.

If any of you have time to review our spreadsheet, please let me know if we are missing something.
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andreas_g



Joined: 30 Jan 2009
Posts: 422
Location: Austria

PostPosted: Wed Apr 19, 2017 2:00 am    Post subject: Reply with quote

I don't know if this is useful, but Previous supports 24 and 96k DSP memory. You could add some debugging output to see what is going on when NeXTstep uses the DSP.
You can find the code here.
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