Subject:
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Re: Mindstorms NXT programming languages
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 13 Jan 2006 19:04:57 GMT
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Viewed:
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2267 times
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In lugnet.robotics, John Barnes wrote:
> Is there an apples and oranges problem here? You are referring to serial memory
> devices used for data storage versus broad side FLASH which permits the CPU to
> execute from it.
>
> If the CPU were to be crippled by executing from a SD memory device, I think
> you'd start complaining about the speed at that point.
>
> So how much does 32 bits wide of 64Mb of FLASH cost?
I think, John, you've finally started us down the right path to (hopefully) put
this whole topic to bed.
What we're talking about here isn't necessarily a difference between serial
FLASH and parallel FLASH. What we're talking about is the difference between
NAND FLASH and NOR FLASH.
The type of FLASH that is used in CF cards nowadays is NAND FLASH. CF uses an
8-bit parallel interface. NAND FLASH requires a file system for access and is
NOT randomly accessible. It is suited for mass storage (such as a CF card).
Products that use NAND FLASH for program storage download the program into DRAM
prior to execution. They do not (can not) run the program from NAND FLASH.
The type of FLASH this is used to run firmware from directly is NOR FLASH.
Although a company like Lego (or any company larger than a garage) would never
buy from Digikey, we can use Digikey as a readily available comparison source:
A 128Mbyte CF card (as was used for comparison earlier in the thread) contains
some combination of NAND FLASH chips that add up to 128M x 8. If you look at
Digikey, you will find that you can do this for about $20 in small quantities.
Given Lego's volumes, their cost will certainly be much less than that, but more
than the high-volume CF card makers can do with their high volumes. Let's say
that it would cost Lego $10 to put 128Mbyte of CF in the NXT. If they didn't
want to make a profit and it didn't cost anything in PCB space or engineering,
they could theoretically do this and only add $10 to the cost of the product.
Of course, it'd be NAND FLASH and would only be useful as a mass storage device,
not code storage.
On the other hand, to add "1000 times" the amount of CODE memory to the NXT,
we'd need 256Mbytes of NOR FLASH (the NXT has 256Kbytes as is). 256Mbytes is
2Gbits. Let's say that we wanted it x32. In that case, we'd be looking for
some combination of NOR FLASH chips to give us 64M x 32. The problem is that
NOR FLASH isn't available in as high of densities as NAND FLASH. To build our
2Mbits of memory, we're looking at possibly 8 256Mbit parts. At $27 each.
Applying our economies of scale, we're talking about over $100 dollars to give
the nxt "1000 times" the amount of FLASH memory. Even assuming that we could
divide that cost by 2 again, given time to find the righ suppliers, we're still
talking about over $50 additional cost, without even looking at the addition PCB
space and engineering time.
Then again, I guess that's a long drawn-out process to go through when we could
have just realized that Lego has already done this.
Thanks for pointing this in the right direction, John. It was kind of
interesting to finally go through the actual thought process.
Mike
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Message has 1 Reply:
 | | Re: Mindstorms NXT programming languages
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| good analysis. Also keep in mind that Lego sells primarily through retail resellers, so their take is considerably less than the SRP. (Even the Lego stores have huge overhead, being in expensive malls). To sell a product like this at < $250 and make (...) (18 years ago, 13-Jan-06, to lugnet.robotics)
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Message is in Reply To:
| | Re: Mindstorms NXT programming languages
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| (...) Er ... Is there an apples and oranges problem here? You are referring to serial memory devices used for data storage versus broad side FLASH which permits the CPU to execute from it. If the CPU were to be crippled by executing from a SD memory (...) (18 years ago, 13-Jan-06, to lugnet.robotics)
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