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| Parallax Forums > Public Forums > Propeller Chip > RAM RAM RAM how much do you need? | Forum Quick Jump
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mctrivia
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Date Joined Jan 2009
Total Posts : 2535
| Posted 11/3/2009 10:11 AM (GMT -8) |   | | | |
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mctrivia
Registered Member
Date Joined Jan 2009
Total Posts : 2535
| Posted 11/3/2009 10:23 AM (GMT -8) | | | | |
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Rsadeika
Registered Member
Date Joined Feb 2005
Total Posts : 633
| Posted 11/3/2009 10:49 AM (GMT -8) | | | Your, cheaper than MIT sales pitch, is not not going to get you very far. If you are looking for a market, think about making some 'shields' for the Propeller Platform Module (PPM). Lets say for about $20, you make a 'shield', fully assembled, with drivers, that has an SD socket, and maybe 512-1024KB of ram. If it is plug&play, than even beginners would not have to much trouble getting involved with the PPM as their first choice. | | Back to Top | | |
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Bill Henning
Registered Member
Date Joined Sep 2006
Total Posts : 962
| Posted 11/3/2009 10:54 AM (GMT -8) | | Hi OBC,
32K is easy and cheap - just get a Microchip 23K256 SPI SRAM chip :) It's a nice easy 8 pin dip, and with a modified version of Kurenko's counter based SD card code should be able to do reads/writes at 20Mbps.
The problem with any memory add-on (or any board as a matter of fact, especially if designed to sell for even a minimal profit) is the overhead costs.
Rough example:
ExpressPCB = $55 or so for 3 boards, making it $18.33 per board. To get cheaper boards, you have to make a lot more of them, but if you know where to go, you can get small boards, qty 100 or so, for $3-$5 each. Less in larger quantities.
Assume you have to do at leat one prototype run. Can't use ExpressPCB - they don't take gerbers. Assume $80-$100 for the initial prototype run.
To get the memory chips at a decent price, you have to buy them in quantity. let's say you buy 100x 512kx8 chips, for just over $3 each.
Now you need at the very least a decoupling capacitor, and some pins... plus some latches if you don't want to use all the prop pins. But let's use the prop pins. say $1 in qty 100 for the caps and the pins/headers.
What do we have so far?
$100 (proto PCB)
$300-$500 (production PCB's)
$350 (100 memory chips)
$100 (cap and pins)
$150 (approx minimum shipping for above)
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$1000-$1200 for 100 saleable boards.
Now let's not forget about all the time spent laying out the board, testing it, chasing down best prices, ordering parts. Or taxes, duties, etc.
Let's not forget having to fork out $1000-$1200 up front before selling a single board.
But for this simple calculation, let's forget labor costs.
Now if you want to sell to distribution, they want 40%-50% off MSRP, so you have to double the sale price just to break even.
So without labor costs counted, and with no profit, you are looking at a for sale price of $20-$24 per board, assuming you sell all boards.
Now if you actually want to be paid even minimally for your time, and want to make even a little profit, you have to double that again.
Now we are at about $40 - $56 for an extremely dumb, simple, 512KB board as a kit, without even a socket for the memory chip, that uses almost all of a propeller's pins (or at least half that if sold directly... but then we have PayPal fees)
And you have zero certainty of selling all the boards.
Using a smaller memory chip, say a 128Kx8, would save you about $1-$2 on parts costs, say $4-$8 on kit price.
Oldbitcollector said...
Please don't take this the wrong way.. (I don't want to kick sand on anyone's project)
It seems that the actual RAM size is significantly increasing the price.
We're all used to dealing with 32K limitation. Any xMB increase would be a huge upgrade,
but honestly I'd be happy with an additional 32K-256K solution, adapted as "standard"
Is this even possible? It seems that if it were the price would be considerably more in line
with what hobbyist budgets (and their spouses) would more easily allow. :)
A smaller $10-$19 solution would be reachable by even our youngest members.
The beauty of the SD solution is that it is high storage at little cost. Can our memory solution match it?
OBC
www.mikronauts.com Please use mikronauts _at_ gmail _dot_ com to contact me off-forum, my PM is almost totally full
Morpheusdual Prop SBC w/ 512KB kit $119.95, Mem+2MB memory IO board kit $89.95, both kits $189.95
Propteus and Proteus for Propeller prototyping 6.250MHz custom Crystals run Propellers at 100MHz
Las - Large model assembler for the Propeller Largos - a feature full nano operating system for the PropellerPost Edited (Bill Henning) : 11/3/2009 7:04:14 PM GMT | | Back to Top | | |
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David B
Registered Member
Date Joined Jul 2004
Total Posts : 319
| Posted 11/3/2009 11:37 AM (GMT -8) | | I could use several megs of RAM for storing a long burst of ADC data, as long as it could be written to at about 5 megasamples per second. The auto-addressing looks helpful for that.
I'd want to see details on how to operate it - address initialization, control pins needed, the time requirements of the various states, and if there are any limitations, such as if the RAM refreshes itself, do you have to halt updates periodically to allow the internal refreshing to take place, and how often and for how long, that sort of thing.
For my current project, I'd want at least a meg, but wouldn't need any more than a few megs, so I wouldn't care about stacking.
I've already used a 512K static RAM chip with hand-wired counters to auto-increment the address for a similar project, and that chip cost something like $17 a few years ago. So I could see paying that price for your board if it would work in my project. | | Back to Top | | |
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mctrivia
Registered Member
Date Joined Jan 2009
Total Posts : 2535
| Posted 11/3/2009 11:44 AM (GMT -8) | | | | |
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mctrivia
Registered Member
Date Joined Jan 2009
Total Posts : 2535
| Posted 11/3/2009 2:51 PM (GMT -8) | | | | |
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Ale
Registered Member
Date Joined May 2007
Total Posts : 1267
| Posted 11/4/2009 6:55 AM (GMT -8) | | | | |
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mctrivia
Registered Member
Date Joined Jan 2009
Total Posts : 2535
| Posted 11/4/2009 6:59 AM (GMT -8) | | | | |
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Ale
Registered Member
Date Joined May 2007
Total Posts : 1267
| Posted 11/4/2009 8:44 AM (GMT -8) | | | | |
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mikediv
Registered Member
Date Joined Dec 2007
Total Posts : 455
| Posted 11/4/2009 10:07 AM (GMT -8) | | Oldbitcollector Wow you just wrote what I have been thinking every time I see a thread for Ram ,, And of course no knock to MC he has awesome stuff and has always shared his knowledge Thank you sir
but Oldbit is spot on about the hobby thing it would be awesome if I could (and have tried) to just wire up 256K or even a 1M I bought a few SPI flash rams from sparkfun actually one is a,, AT45DB161D,,16Meg with a carrier board for 6 dollars but I do not posses the software skills to get it to work. I fully understand MC the need to be able to make money and I mean no insult but a even a $20 dollar ram kit with software would be such a great upgrade especially for us neewbies my coding skill are so lacking that my code is huge and I always run out of ram
mctrivia is there anyway a a quantity purchase from you would make it economically visible for you to build say an"AT45DB161D" kit that would work with the prop chips????? Please understand I claim no special knowledge of how to do this
just asking out loud. | | Back to Top | | |
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mctrivia
Registered Member
Date Joined Jan 2009
Total Posts : 2535
| Posted 11/4/2009 10:24 AM (GMT -8) | | | | |
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