NERDYCLAP : A Geeky Parlance

I had a task to compare different protocols( and their different implementations) like SD, SPI, SDIO(in FreeBSD's MMCCAM implementation) by accessing SD Card. Now, for unbiased comparison, i must eliminate file system type in sd card from the equation. In this blog post, i'll discuss/share my findings about how file-system on a card(SD and MMC) affect its performance. So, let's start with a very quick introduction to some basic concepts: Introduction MMC- M ulti m edia C ard is a memory card unveiled in 1997 by SanDisk and Siemens based on NAND flash memory. eMMC is a regular MMC in a BGA package. SD Card: S ecure D igital Card was introduced in 1999 based on MMC but adding extra features such as security. INSIDE MMC [caption id="" align="alignright" width="321"] https://www.ibm.com/developerworks/linux/library/l-flash-filesystems/figure1.gif[/caption] MMC is made up of broadly 3 parts: MMC interface - Responsible for handling communi...

This blog post presents a gist of Free BSD's doc on CAM( here ) and chapter 14 of the book FreeBSD device driver- A guide for intrepid. It gives an introduction to the CAM(Common access method), it's applications, it's working and it's organization in FreeBSD. It is written to get myself a really good understanding of mmccam stack which is nothing but SDHC/SDIO protocols wired within the CAM framework. COMMON ACCESS METHOD CAM is a method for separating HBA adapters from storage adapters and is primarily used for SCSI. By separating these drivers it reduces the complexity of both the drivers.Furthermore, this separation enables storage drivers (such as CD-ROM and tape drivers) to control their devices on any I/O bus (such as IDE, SCSI, and so on) as long as an appropriate HBA driver is available. Note: HBA(Host Bus Adapters) are devices (IC/Card) that connects the host to other devices. For example, USB HBA allows host OS to communicate to USB. In CAM terminology, HBA ...

    In this blog post i will present the gist of the paper http://www.kaltech.co.il/pdf/Eureka_sd_wp1.pdf ,  It's crucial for anyone willing to understand how removable devices like sd card work, different protocols/functionalities they support. Secure Digital (SD) memory card today, is one of the most popular non-volatile removable data storage media for consumer applications. It's not intended to remove hard-disk. Hard-disk can still deliver much better speed and memory capacity. SD card is used in applications demanding optimum memory capacity, smaller size, and low end product cost.  The combination of small foot print, lower cost and optimal performance contributed in SD-card's success. What is MultiMedia Card (MMC)? MMC and Sd-card share many common features and have the same physical and electrical specifications. The differences between the two standards are mainly on the software level commands. The similarities allow many hosts to accept both MMC and SD cards on ...