View Full Version : Everyone loves RAM

Graham Stabler
01-10-2008, 06:51 PM
Everyone wants more RAM and one way to get it is with external RAM chips and possibly a CPLD etc but I was wondering if Parallax would or could create there own RAM device with an integrated interface particularly suited for the propeller and its programmers, something easy to set up and drive and with handy modes such as FIFO, pseudo DMA etc. This would allow for three chip (prop, RAM, ROM) super systems.

I'm afraid I'm ignorant of the practicalities of such an idea but I thought I would put it out there in cased it wasn't totally mad.


01-10-2008, 09:33 PM

I think Andre is on that track. With his new card, you even get a CPLD, which you can re-program (that's a capital "YOU"... not the little "me" :)

Problem is that the key info for the card is on a CD, which you don't get to see unless you buy the card. I looked around for a technical description of his new card for the Hydra and had great difficulty finding it. I don't know if there is a limited supply, if Andre really doesn't want to sell the new cards or what, but I think that card is the best kept secret in the Prop world:)

I think this would be another great section for the Propeller Cookbook.


01-10-2008, 10:00 PM
Are you referring to the Hydra 128K Expansion board?

Item code 32361, Price $29.95


Mike Green
01-10-2008, 10:18 PM
The Hydra 128K Expansion board adds a second 128K EEPROM plus some expansion wiring area, but no RAM.

The RAM card is described here:
www.parallax.com/Store/Microcontrollers/PropellerTools/tabid/143/CategoryID/19/List/0/SortField/0/Level/a/ProductID/444/Default.aspx (http://www.parallax.com/Store/Microcontrollers/PropellerTools/tabid/143/CategoryID/19/List/0/SortField/0/Level/a/ProductID/444/Default.aspx)

Post Edited (Mike Green) : 1/10/2008 3:26:17 PM GMT

01-10-2008, 10:29 PM
More likely this one ...

www.parallax.com/Store/Microcontrollers/PropellerTools/tabid/143/CategoryID/19/List/0/SortField/0/Level/a/ProductID/444/Default.aspx (http://www.parallax.com/Store/Microcontrollers/PropellerTools/tabid/143/CategoryID/19/List/0/SortField/0/Level/a/ProductID/444/Default.aspx)

The HYDRA Xtreme Manual explains teh workings, describes the CPLD, reprogramming and includes the CPLD re-programming interface.

01-10-2008, 10:44 PM
Oh yes - I got the wrong card, thanks for the corrections...

There's a thread on adding RAM here http://forums.parallax.com/showthread.php?p=618562, I think this is in the Sticky good thread index...


Graham Stabler
01-10-2008, 10:48 PM

I was aware of those cards "external RAM chips and possibly a CPLD etc" but they are not practical for many applications (too big) hence my post.


Graham Stabler
01-10-2008, 10:49 PM
Oh when I ask if Parallax could create there own RAM device I mean a single IC


01-11-2008, 12:10 AM
how much ram are you after? if it's ~32K they do already it's called a second propeller :)

Graham Stabler
01-11-2008, 01:52 AM
I'm not after any amount in particular but I guess I was thinking of larger amounts suitable for image capture and the like.


01-11-2008, 02:55 AM
Something like 128K sram?
Don't forget you've gotta be able to get the address and CE etc then data fast enough for it to be usable, so tbh you'd need something like a small cpld ( like HX512 setup ) where cpld can be given start address etc, then just burst read / write from that address, then the cpld handles all the pre-post inc/decrementing for you, instead of the cog struggling to keep up.


PS, and unlike hubram, only 1 COG will be able to assist with accessing the extra ram.

01-11-2008, 05:09 AM
I found adding a 32k FRAM (Ramtron FM31256) gave me what I needed, plus clock and 2 event counters, all on the same I2C bus as the boot eeprom.

Paul Baker
01-11-2008, 05:19 AM
If you're looking for (relatively) easy to use video memory, you can use the CY7C09089V: http://rocky.digikey.com/WebLib/Cypress/Web%20Data/CY7C09079V,89V,99V,%20CY7C09179V,89V,99V.pdf·64KB of dual port RAM with burst mode, fill it up via one port connected to the Propeller, drive the video from the other port in burst mode. But this ease of use doesn't come cheap, the chip costs $38 (and it is not RoHS compliant).

Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
[/url][url=http://www.parallax.com] (http://www.parallax.com)
Parallax, Inc. (http://www.parallax.com)

Graham Stabler
01-11-2008, 06:03 AM
Baggers, the function of the CPLD could be built into the RAM chip presumably if it was custom.

Again I have no real application I'm just trying to suggest that the kinds of devices many people would like to see do not exist (except for $38) and I wondered if parallax could create the hobbiests dream RAM chip complete with built in interfacing logic.


01-11-2008, 12:02 PM
How about driving DRAM SIMMs salvaged from old PC's? Just needs some really cheap glue logic to save I/O pins.

01-11-2008, 01:10 PM
VIRAND said...
How about driving DRAM SIMMs salvaged from old PC's? Just needs some really cheap glue logic to save I/O pins.

DRAM SIMMs have to be refreshed though. And they're not exactly fast. I just checked a stick from a stash of old memory I have and it runs at 70ns. Also good luck finding a socket for SIMMs.

Dennis Ferron
01-11-2008, 01:37 PM
Interestingly, if you do manage to find a socket for sims (I got 1 from a surplus store) it will fit perfectly on a breadboard. On 30 pin sims, the pin spacing is the same as DIP chips.

01-11-2008, 03:46 PM
70 nanoseconds seems fast enough for me;
if I calculated right it's 14 Megabytes (or Mbits or Mnybbles if using only one DRAM chip) per second.

Refresh requirement probably is 1024 reads every 4 milliseconds. Such as if using some of the DRAM as the video buffer.

Why not solder onto a simm? How about soldering header pins on it?

01-11-2008, 03:56 PM
When using a COG as DRAM controller it can of course do the refresh as well: around 10 additional instructions http://forums.parallax.com/images/smilies/smile.gif

01-13-2008, 03:14 AM
Jameco sells 30-pin sockets (http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=100302&pa=100302PS) for $1 each. The SIMMs themselves are pretty common on Google's product search engine - tried a quick search for 4MB and they pop up around $5. 16MB pops up at around $20. Nice cheap easily soldered memory.

Not that I need to order SIMMs any myself. I just found 13 in a small memory box I dug up from old $5 386s. I think I have some 256KB ones someplace. :D

Post Edited (Frobozz) : 1/12/2008 8:19:27 PM GMT

Mike Popoloski
01-13-2008, 08:46 PM
Just out of curiosity, what would be the speed differences between this DRAM version and the more complex SRAM with CPLD controller? Enough to discredit the use of the DRAM as video memory?

Oldbitcollector (Jeff)
01-13-2008, 08:56 PM
Perfect would be 30pin SIPPs
(30 pin SIMM with pins) but I haven't seen one of these in years...


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01-14-2008, 09:52 PM
eBay has a few SIPPs and a good number of 30/72-pin SIMMs for sale.

search.ebay.com/search/search.dll?ht=1&from=R4&satitle=sipp&sacat=58058%26catref%3DC6 (http://search.ebay.com/search/search.dll?ht=1&from=R4&satitle=sipp&sacat=58058%26catref%3DC6)
search.ebay.com/search/search.dll?ht=1&from=R4&satitle=simm&sacat=58058%26catref%3DC6 (http://search.ebay.com/search/search.dll?ht=1&from=R4&satitle=simm&sacat=58058%26catref%3DC6)

Edit: Where is a good document detailing how to use 30-pin SIMMs? I've searched JEDEC but their site got changed and
now I can't find anything. I hate it when something gets changed for the worse.

Post Edited (Frobozz) : 1/14/2008 4:36:34 PM GMT

Phil Pilgrim (PhiPi)
01-15-2008, 02:19 AM
A good source for legacy DRAM chips and modules is Jameco. I'm not sure I'd want to design an actual product around these, though, since they're not made anymore. Nonetheless, they seem like a good match for the Propeller's capabilities and pin count.