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List:       linux-kernel
Subject:    Re: CONFIG_TINY
From:       Eli Carter <eli.carter () inet ! com>
Date:       2002-11-04 22:30:11
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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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