Template talk:MultiMediaCard comparison
|WikiProject Electronics||(Rated Template-class)|
The specs shown here for SD appear to also contain specs for SDHC (e.g. 50MHz, 200Mb/s). Firstly, these specs are not denoted as such, and secondly, these higher specs also apply to miniSDHC and microSDHC. Does anyone object to my adding these notations to the SD, miniSD, and microSD columns? EJSawyer (talk) 20:45, 16 March 2008 (UTC)
The footer on this indicates that all of these formats has a max capactiy of 128GB. However, it's clear that (within the "official" specs) there is a ceiling of 2GB for all standard MMC/SD formats (SDHC and MMC Plus break the ceiling). Granted, there are non-standard cards (especially SD) that are greater than 2GB, but these are proprietary cards that are not compatible with the majority of devices. Does anyone object to such an edit? EJSawyer (talk) 21:01, 16 March 2008 (UTC)
- I've added a new line in the chart of the available capacities between certain devices.
- I felt it's very important it should be there. Besides I think it would be great adding extra columns for SDXC etc.
- Bottom line, this chart will be ready by non-geeks as well and thus should supply quick handy info too.--Weitzhandler (talk) 00:30, 1 August 2012 (UTC)
4-bit Mode optional ?
The SD column (and miniSD/microSD columns) have the 4-bit mode marked as "Optional". Is that really correct? The SD Simplified spec contains a sentence saying:
"Since the SD Memory Card shall support at least the two bus modes 1-bit or 4-bit width, then any SD Card shall set at least bits 0 and 2" (with bit 0 and 2 meaning 1-bit and 4-bit mode support respectively).
The "or" in "1-bit or 4-bit" is quite confusing, some manufacturers might even interprete it as 1-bit mode being optional (which would be almost certainly wrong). But the way how I am interpreting that sentence is that it appears to say that all SD Cards must support both 1-bit and 4-bit mode.
Or are there any sources indicating that 4-bit mode would be optional for SD cards? Are there any older SD specs that are lacking 4-bit mode? Did any manufacturers ever produce SD cards without 4-bit mode support?220.127.116.11 (talk) 23:39, 19 November 2014 (UTC)
- I haven't read the FREE specs in a while, so I spent some time searching and reading various parts of it. It kind of says that both 1-bit SD bus and 4-bit SD bus are both suppose to exist. In the SDIO spec, it clearly says that 4-bit SD bus is optional. I know for a fact that 1-bit MMC/SD bus mode is mandatory on all cards, because they start in that mode at power-up. The bottom line is software should always read the SD_BUS_WIDTHS field in the SCR register before trying to enable 4-bit SD bus mode, thus the software will always work. Though SPI bus mode is optional in MMC cards, I think they all include it, per what I've seen people talk about on the internet over the past years, and these days it really doesn't matter anymore since SD cards are common and dirt cheap and MMC are hard to find. • Sbmeirow • Talk • 08:18, 20 November 2014 (UTC)
- MMC cards are rare nowadays. The MMC protocol seems to have had some revival for non-removeable onboard BGA chips, exceeding the 2GB limit, see KMCEN0000M datasheet, for example. According to the datashet, that chip seems to lack SPI bus. I don't know if those BGAs are widely used though; the Nintendo DSi is using one (with smaller capacity of only 256Mbyte).2OO.3OO.2OO.3OO (talk) 18:38, 24 November 2014 (UTC) PS. what I meant is called eMMC, it's already mentioned in wikipediea MMC article. 2OO.3OO.2OO.3OO (talk) 23:03, 24 November 2014 (UTC)