From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: SD 3.00 Physical layer FULL specification Date: Sat, 1 Sep 2012 20:19:00 +0000 Message-ID: <201209012019.00183.arnd.bergmann@linaro.org> References: <20120901022755.10343.qmail@science.horizon.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Return-path: Received: from moutng.kundenserver.de ([212.227.17.9]:61588 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754659Ab2IBSuF (ORCPT ); Sun, 2 Sep 2012 14:50:05 -0400 In-Reply-To: <20120901022755.10343.qmail@science.horizon.com> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: George Spelvin Cc: linux-mmc@vger.kernel.org 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