Re: CONFIG_TINY

Eli Carter
2002-11-04T22:23:40Z

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Rob Landley wrote:
> On Monday 04 November 2002 20:34, Cort Dougan wrote:
>
>>I'm with you on that. People who clammer ignorantly about image size
>>without looking at what they actually need should have opened their eyes in
>>the last few years. Flash and RAM sizes under 32M are nearly unheard of
>>now-a-days.
>
>
> How much power does flash eat? I was under the impression half the reason for
> tiny amounts of memory was to increase battery life in things that really
> should last weeks or months instead of hours (wristwatches, cell phones on
> standby, etc), but I guess that's mostly a question of dram and sram, not
> flash. (I take it you can read the heck out of it without wearing it out,
> it's just writes that are a problem... Then again you don't want rapidly
> rewritten bookkeeping stuff in flash, do you? (Jiffies, scheduler stuff,
> etc, should not be in flash...))

There a couple of kinds of flash memory that have different properties
in the writes...
The one I'm more familiar with allows you to change any '1' bit to a '0'
bit on a bit-by-bit basis, but it is, ehm, a tad slow. But if you want
to change a '0' bit to a '1' bit, you have to erase a 16 or 32 kB block
to all '1' bits, and that is, well, very slow.
(Storing 'jiffies' in flash, given that updating the jiffies would take
multiple jiffies would be, well, 'fun'. ;) I could, however, see some
sense in running the read-only parts of the kernel directly from flash...)
It's been a while since I looked at read times, but I expect it to be
essentially memory speeds.

> Not my area, I'm afraid...
>
> Rob

Just an FYI, in case you're curious.

Eli
--------------------. "If it ain't broke now,
Eli Carter \ it will be soon." -- crypto-gram
eli.carter(a)inet.com `-------------------------------------------------

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