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RE: Repeater and the CFC
>I saw your list of recommended CFC cards, included the SanDisk brand, but
>didn't include the 64mb card. Would you recommend that card? I ask because
>there is a pretty good deal on these at my local Costco.
It depends... The Sandisk cards work, they will record in stereo, and is
very reliable cards. However the ones we tested did seem to have some minor
speed limitations with Repeater. With the cards tested, I was only able to
record in stereo for about 3.5 minutes before repeater reports "CFC Slow"
and it stops recording (mono went for the entire 8 minutes with no
problems). This only comes up when you have a 64 MB card or higher, OR if
you are making extreeeeeeeeeeeemly long loops, OR if you are using Repeater
as a digital hard disk recorder because you went out and bought a 512 MB
card. Considering most loops are only seconds long it's probably only a
minor limitation. The newer DaneElec and Simple tech cards seem to have no
speed limitations with Repeater. Full stereo recording up to 8 minutes
If you don't mind the minor speed limitations then you are probably o.k.
will be very happy with the Sandisk card you are eyeballing. See if you can
arrange to try before you buy or get a return grantee and then you won't
have to worry.
The following was written to the list earlier by Don, one of the brainiacs
at Electrix who sweated blood to bring Repeater to life.
1. The following is based on my experience and is my personal
opinion. It should not be taken to represent the official views
or position of Electrix/IVL Technologies. (even though the
conclusion is pretty much exactly the same).
2. The following only relates to CFC cards in the context of
their use with Repeater, and implies nothing about their
suitability or performance with ANY OTHER PRODUCT.
3. If you think I am being paranoid, I have been flamed badly
in the past. All this having been said, flame proof underpants
on and here goes...
I noticed the discussion starting around CFC buys. There is some
stuff on the Electrix website, and also on a flyer shipped with the
unit. However you do need to be aware of card specs - the only
real way to know things are going to be cool is to test Repeater
with the card you wish to use. Until specifications become a
perfect art, rather than a marketting tool, that is just the way it
Electrix has been doing a lot of testing with different CFC cards,
and our recommendations are based on the results of those
CFC card specs that are published from different manufacturers
seem to cover the following:
Burst-mode rate (quoted ~6-10MB/sec). Ignore this. Unfortunately
everyone who designs a CFC interface needs to design for the
lowest common denominator anyway, making this spec worse than
Read rate. Typically 800KB/sec -> 2MB/sec. Read rate is not
really the issue. Reading flash memory is pretty damn quick and
in Repeater accounts for a fairly small proportion of the time
consumed at the CFC interface.
Write rate. Quoted (ahem!) 500KB/sec -> 1.5MB/sec. However
this is the long-term sustained rate, and depending on the card
manufacturer, the data caching algorithms they use, and a whole
load of other variables the short-term variance in write operation
latency can be huge. I know - I have pored over the logic analyser
and scope traces looking into this phenomenon until I went bug
eyed [still in recovery...].
CFC cards do some pretty nifty footwork under the hood to manage
the storage medium - including error recovery, bad sector
remapping, wear levelling etc... Also, writing is a cached
mechanism and there are additional time effects due to the caching
scheme used, the pattern of writes to the card and the amount of
The result of all of this is that an apparently fast card may
occasionally (or in the case of one card we tested, very often...)
take a long time to complete a write operation. Hit a few of these
long write operations in a row and all of a sudden Repeater will
have run out of write buffer space and will inform you that there is
an issue here...
Most cards will handle the 'sequential' writing of mono operation
with no problems. Stereo operation is where most problems lie.
The pattern of writes to two .wav files can fight with the CFC
caching scheme and cause the card performance to be somewhat
less than desirable.
So - that is the low down.
My advice is to read the specs (the faster card manufacturers will
quote them with pride. The slower card manufacturers will quote
them under a subtle disguise to make you think they are better
than they are...). Take all specs with a healthy dose of reserve.
Then, if you can test a card before you buy, do. We are providing
information on cards we have thoroughly tested and are happy with
to help with purchase decisions.
The Simple Technologies cards deliver. DaneElec also are just
dandy. This does not imply that other cards out there will not
also do just fine, but it provides a starting point. I hope that with
experience that this forum will provide more information about
good card choices for use with Repeater. We will also update
the information on the web site as more experience and test
results become available.
Please consult the website and feel free to post questions
for us folks about CFC cards. We will be happy to occasionally
break the lurking mode and provide what information we can.
Cheers, and I hope you folks have a *lot* of fun...
(of Rik Elswit's 'Don and the Maniacs' fame... I kind of like that
ps. CFC technology is moving *damn* quick these days, and the
speed of cards will become less of an issue as time goes on. With
Repeater we had to design towards where we expected CFC
technology to be, and fortunately our Crystal Ball did a pretty good
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