From: Arnd Bergmann <arnd.bergmann@linaro.org>
To: George Spelvin <linux@horizon.com>
Cc: linux-mmc@vger.kernel.org
Subject: Re: SD 3.00 Physical layer FULL specification
Date: Sat, 1 Sep 2012 20:19:00 +0000 [thread overview]
Message-ID: <201209012019.00183.arnd.bergmann@linaro.org> (raw)
In-Reply-To: <20120901022755.10343.qmail@science.horizon.com>
On Saturday 01 September 2012, George Spelvin wrote:
> In particular, it documents the FAT update optimizations in SD cards
> (section 4.3.1.7, p. 112).
>
> If anyone cares, write performance is defined in terms of updates to
> "allocation units" (i.e. erase blocks) 512K-4MiB in size of a card-defined
> size, which are made up of "recording units" (i.e. FAT clusters).
> Table 4-51 on p. 113 gives the limits.
I believe these recommendations are often ignored anyway. A lot of the
SD cards nowadays have erase block sizes of 1.5, 3, 6, or 8 MB. None
of these can be specified with this version of the standard. Even for
the rare cards that have 1MB or 2MB erase block sizes, I've never seen
one that reports anything but 4MB.
Arnd
prev parent reply other threads:[~2012-09-02 18:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-01 2:27 SD 3.00 Physical layer FULL specification George Spelvin
2012-09-01 20:19 ` Arnd Bergmann [this message]
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