Okay, using Compact Flash (CF) and Smart Media cards to boot a
computer and for use as a long term backup medium is a Really Bad Idea.
Use Flash RAM for what it is marketed at, use it for transferring small
files or as storage for small portable devices such as digital cameras
or MP3 players.
First off, CF cards are much slower than even the slowest hard
drive. Despite what its name might indicate reading and writing from
Flash RAM is a very slow process. On top of that CF cards use a
primitive form of IDE that in addition to having a very low data
transfer rate, is very CPU intensive. Once, I ran a benchmarking
program on a 1400/166 using both its internal 6GB drive and a CF card.
Even though the hard drive I/O speed on a 1400 is probably about a third
the speed of a 2400, due to a lack of IDE DMA on the 1400, the flash RAM
ran the same tests three times slower than the hard drive on the 1400.
Second off Flash RAM can only be written to so many times before
bits start locking into position, corrupting what files there are on the
Flash RAM. How long does it take to kill flash RAM? I don't know
exactly. Several years ago Flash RAM modules were designed for 100,000
read/write cycles. However, a few years ago I heard about new
technologies from Flash RAM manufacturers like Intel, the dominant Flash
RAM manufacturer, which could be in use now, that would double the size
of Flash RAM but reduce the number of read/write cycles to 10,000. In
either case I'm not exactly sure how much time it would take to kill
flash RAM if it was used for a Mac system disk. However, I do know that
a couple of years ago a company sold an x86 PC with a small flash RAM
disk that was essentially like a CF card. This machine was often hacked
to run OSes that it didn't come with. At any rate some people thought
to use the Flash RAM disk as a virtual memory partition in Linux. The
poor Flash RAM disk generally didn't last more than a couple of hours
under this kind of usage before it kicked the bucket. Granted, these
machines had little main memory in the first place and virtual memory in
Linux is written to and read from quite a bit. However, even with
virtual memory off in the MacOS you are probably looking at a time frame
of less than a couple of months before failure. Though with the glacial
speed of Flash RAM I don't know why you would want to do this in the
first place.
Another problem with some of the cheaper CF cards and CF card
adaptors is that the contacts can be poorly made. The result is that
the contacts can break after repeated matings and unmatings. Poorly
made connectors can also corrode under humid conditions making it so
that good electrical contact cannot be made.
At any rate, this is probably too much information. :)
On Saturday, May 4, 2002, at 04:43 PM, Ralph Mawyer wrote:
> Unless mac2400 crashed like my harddrive did last Sunday, there's a
> whole section on the use of CF and SmartMedia cards for booting up,
> etc. (BTW, HD failure is a wonderful way to simplify your life if you
> haven't backed up...almost worth going through the archives to get all
> of Sidney's(with an 'i') posts back on my drive.
>
> 128MB Smart Media cards are under $50 now so probably worth checking
> out. I think the CF cards tend to be even cheaper and bigger.
>
>> Has anyone used a compactflash RAM card in a 2400 for anything? If so,
>> are there have any warnings? Are there things for which this is not a
>> good idea? How does it compare to a RAMdisk in terms of speed, in
>> particular
>> (are they much slower than the on-board RAM)? Can I just get a vanilla
>> card and adapter and use them? Are there special types of RAM cards I
>> should look for or avoid?
>>
>> Thanks in advance.
>>
>> PB Schechter
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