Anastasia Klimchuk has uploaded this change for review. ( https://review.coreboot.org/c/flashrom/+/83584?usp=email )
Change subject: doc: Add overview doc for user_docs ......................................................................
doc: Add overview doc for user_docs
This document is converted from Technology page on wiki https://wiki.flashrom.org/Technology
Change-Id: I93107d6b5530c301dd90f7177758632d9d1810eb Signed-off-by: Anastasia Klimchuk aklm@flashrom.org --- A doc/user_docs/Amd_am29f010_tsop32.jpg A doc/user_docs/Bios_savior.jpg A doc/user_docs/Dip32_chip.jpg A doc/user_docs/Dip32_chip_back.jpg A doc/user_docs/Dip32_in_socket.jpg A doc/user_docs/Dip8_chip.jpg A doc/user_docs/Dip8_chip_back.jpg A doc/user_docs/Dip8_in_socket.jpg A doc/user_docs/Dip_tool.jpg A doc/user_docs/Dual_plcc32_soldered.jpg A doc/user_docs/Empty_dip32_socket.jpg A doc/user_docs/Empty_dip8_socket.jpg A doc/user_docs/Empty_plcc32_socket.jpg A doc/user_docs/Flash-BGA.jpg A doc/user_docs/Plcc32_chip.jpg A doc/user_docs/Plcc32_chip_back.jpg A doc/user_docs/Plcc32_in_socket.jpg A doc/user_docs/Plcc_tool.jpg A doc/user_docs/Pushpin_roms_2.jpg A doc/user_docs/Soic8_chip.jpg A doc/user_docs/Soic8_socket_back.jpg A doc/user_docs/Soic8_socket_front_closed.jpg A doc/user_docs/Soic8_socket_half_opened.jpg A doc/user_docs/Soic8_socket_open.jpg A doc/user_docs/Soic8_socket_with_chip.jpg A doc/user_docs/Soic8_socket_with_chip_inserted.jpg A doc/user_docs/Soldered_plcc32.jpg A doc/user_docs/Soldered_tsop40.jpg A doc/user_docs/Soldered_tsop48.jpg A doc/user_docs/Spi-socket-dscn2913-1024x768.jpg A doc/user_docs/Sst_39vf040_tsop32.jpg A doc/user_docs/Top_hat_flash.jpeg M doc/user_docs/index.rst A doc/user_docs/overview.rst 34 files changed, 302 insertions(+), 0 deletions(-)
git pull ssh://review.coreboot.org:29418/flashrom refs/changes/84/83584/1
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+ overview fw_updates_vs_spi_wp example_partial_wp chromebooks diff --git a/doc/user_docs/overview.rst b/doc/user_docs/overview.rst new file mode 100644 index 0000000..1b3fe40 --- /dev/null +++ b/doc/user_docs/overview.rst @@ -0,0 +1,301 @@ +========== +Overview +========== + +Modern mainboards store the BIOS in a reprogrammable flash chip. +There are hundreds of different flash (`EEPROM https://en.wikipedia.org/wiki/EEPROM`_) chips, +with variables such as memory size, speed, communication bus (Parallel, LPC, FWH, SPI) and packaging to name just a few. + +Packaging/housing/form factor +============================= + +DIP32: Dual In-line Package, 32 pins +------------------------------------ + +DIP32 top + +.. image:: Dip32_chip.jpg + :alt: DIP32 top + +DIP32 bottom + +.. image:: Dip32_chip_back.jpg + :alt: DIP32 bottom + +DIP32 in a socket + +.. image:: Dip32_in_socket.jpg + :alt: DIP32 in a socket + +DIP32 socket + +.. image:: Empty_dip32_socket.jpg + :alt: DIP32 socket + +DIP32 extractor tool + +.. image:: Dip_tool.jpg + :alt: DIP32 extractor tool + +A rectangular black plastic block with 16 pins along each of the two longer sides of the package +(32 pins in total). DIP32 chips can be socketed which means they are detachable from the mainboard +using physical force. If they haven't been moved in and out of the socket very much, +they can appear to be quite difficult to release from the socket. One way to remove a DIP32 chip +from a socket is by prying a **thin screwdriver** in between the plastic package and the socket, +along the shorter sides where there are no pins, and then gently bending the screwdriver to push +the chip upwards, away from the mainboard. Alternate between the two sides to avoid bending the pins, +and don't touch any of the pins with the screwdriver (search about ESD, electro-static discharge). +If the chip is **soldered directly to the mainboard**, it has to be desoldered in order to be +reprogrammed outside the mainboard. If you do this, it's a good idea to +`solder a socket to the mainboard http://www.coreboot.org/Soldering_a_socket_on_your_board`_ instead, +to ease any future experiments. + +PLCC32: Plastic Leaded Chip Carrier, 32 pins +-------------------------------------------- + +PLCC32 top + + .. image:: Plcc32_chip.jpg + :alt: PLCC32 top + +PLCC32 botto + + .. image:: Plcc32_chip_back.jpg + :alt: PLCC32 bottom + +PLCC32 socket + + .. image:: Plcc32_in_socket.jpg + :alt: PLCC32 socket + +PLCC32 in a socket + + .. image:: Empty_plcc32_socket.jpg + :alt: PLCC32 in a socket + +Soldered PLCC3 + + .. image:: Soldered_plcc32.jpg + :alt: Soldered PLCC32 + +Two soldered PLCC32 + + .. image:: Dual_plcc32_soldered.jpg + :alt: Two soldered PLCC32 + +PLCC32 Bios Savior + + .. image:: Bios_savior.jpg + :alt: PLCC32 Bios Savior + +PLCC32 Top-Hat-Flash adapte + + .. image:: Top_hat_flash.jpeg + :alt: PLCC32 Top-Hat-Flash adapter + +PLCC32 pushpin trick + + .. image:: Pushpin_roms_2.jpg + :alt: PLCC32 pushpin trick + +PLCC extractor tool + + .. image:: Plcc_tool.jpg + :alt: PLCC extractor tool + +Black plastic block again, but this one is much more square. +PLCC32 was becoming the standard for mainboards after DIP32 chips because of its smaller physical size. +PLCC can also be **socketed** or **soldered directly to the mainboard**. +Socketed PLCC32 chips can be removed using a special PLCC removal tool, +or using a piece of nylon line tied in a loop around the chip and pulled swiftly straight up, +or bending/prying using small screwdrivers if one is careful. PLCC32 sockets are often fragile +so the screwdriver approach is not recommended. While the nylon line method sounds strange it works well. +Desoldering PLCC32 chips and soldering on a socket can be done using either a desoldering station +or even just a heat gun. You can also cut the chip with a sharp knife, **but it will be destroyed in the process, of course**. + +DIP8: Dual In-line Package, 8 pins +---------------------------------- + +DIP8 top + + .. image:: Dip8_chip.jpg + :alt: DIP8 top + +DIP8 bottom + + .. image:: Dip8_chip_back.jpg + :alt: DIP8 bottom + +DIP8 in a socket + + .. image:: Dip8_in_socket.jpg + :alt: DIP8 in a socket + +DIP8 socket + + .. image:: Empty_dip8_socket.jpg + :alt: DIP8 socket + +Most recent boards use DIP8 chips (which always employ the SPI protocol) or SO8/SOIC8 chips (see below). +DIP8 chips are always **socketed**, and can thus be easily removed (and hot-swapped), +for example using a small screwdriver. This allows for relatively simple recovery in case of an incorrectly flashed chip. + +SO8/SOIC8: Small-Outline Integrated Circuit, 8 pins +--------------------------------------------------- + +Soldered SOIC8 + + .. image:: Soic8_chip.jpg + :alt: Soldered SOIC8 + +SOIC8 socket, front, closed + + .. image:: Soic8_socket_front_closed.jpg + :alt: SOIC8 socket, front, closed + +SOIC8 socket, half open + + .. image:: Soic8_socket_half_opened.jpg + :alt: SOIC8 socket, half open + +SOIC8 socket, open + + .. image:: Soic8_socket_open.jpg + :alt: SOIC8 socket, open + +SOIC8 socket, back + + .. image:: Soic8_socket_back.jpg + :alt: SOIC8 socket, back + +SOIC8 socket, chip nearby + + .. image:: Soic8_socket_with_chip.jpg + :alt: SOIC8 socket, chip nearby + +SOIC8 socket, chip inserted + + .. image:: Soic8_socket_with_chip_inserted.jpg + :alt: SOIC8 socket, chip inserted + +Another type of SOIC8 adapter + + .. image:: Spi-socket-dscn2913-1024x768.jpg + :alt: Another type of SOIC8 adapter + +Similarly to the DIP8 chips, these always use the SPI protocol. +However, SO8/SOIC8 chips are most often soldered onto the board directly without a socket. +In that case a few boards have a header to allow :doc:`in-system`. You can also desolder +a soldered SO8 chip and solder an SO8 socket/adapter in its place, or build +a `SOIC-to-DIP adapter http://blogs.coreboot.org/blog/2013/07/16/gsoc-2013-flashrom-week-4/`_. +Some of the cheapest SOIC ZIF sockets are made by `Wieson https://www.wieson.com/go/en/wieson/index.php?lang=en`_. +They have 3 models available - G6179-10(0000), G6179-20(0000) and a 16 pin version named G6179-07(0000). +They are available for example from `siliconkit https://siliconkit.com/oc3/`_, +`Dediprog https://www.dediprog.com/`_, as well as `alibaba http://alibaba.com/`_. +For the usual "BIOS" flash chips you want the G6179-10 model (look also for G6179-100000). +Dediprog usually has them or similar ones as well but has steep shipping costs and an unpractical minimum order quantity. + +TSOP: Thin Small-Outline Package, 32, 40, or 48 pins +---------------------------------------------------- + +Soldered TSOP32 + + .. image:: Amd_am29f010_tsop32.jpg + :alt: Soldered TSOP32 + +Soldered TSOP32 + + .. image:: Sst_39vf040_tsop32.jpg + :alt: Soldered TSOP32 + +Soldered TSOP40 + + .. image:: Soldered_tsop40.jpg + :alt: Soldered TSOP40 + +Soldered TSOP48 + + .. image:: Soldered_tsop48.jpg + :alt: Soldered TSOP48 + +TSOPs are often used in embedded systems where size is important and there is no need +for replacement in the field. It is possible to (de)solder TSOPs by hand, +but it's not trivial and a reasonable amount of soldering skills are required. + +BGA: Ball Grid Array +-------------------- + +BGA package flash + + .. image:: Flash-BGA.jpg + :alt: BGA package flash + +BGAs are often used in embedded systems where size is important and there is no need +for replacement in the field. It is not easily possible to (de)solder BGA by hand. + +Communication bus protocol +========================== + +There are four major communication bus protocols for flash chips, +each with multiple subtle variants in the command set: + +* **SPI**: Serial Peripheral Interface, introduced ca. 2006. +* **Parallel**: The oldest flash bus, phased out on mainboards around 2002. +* **LPC**: Low Pin Count, a standard introduced ca. 1998. +* **FWH**: Firmware Hub, a variant of the LPC standard introduced at the same time. + FWH is a special case variant of LPC with one bit set differently in the memory read/write commands. + That means some data sheets mention the chips speak LPC although + they will not respond to regular LPC read/write cycles. + +Here's an attempt to create a marketing language -> chip type mapping: + +* JEDEC Flash -> Parallel (well, mostly) +* FWH -> FWH +* Firmware Hub -> FWH +* LPC Firmware -> FWH +* Firmware Memory -> FWH +* Low Pin Count (if Firmware/FWH is not mentioned) -> LPC +* LPC (if Firmware is not mentioned) -> LPC +* Serial Flash -> SPI + +SST data sheets have the following conventions: + +* LPC Memory Read -> LPC +* Firmware Memory Read -> FWH + +If both are mentioned, the chip supports both. + +If you're not sure about whether a device is LPC or FWH, look at the read/write cycle definitions. + +FWH + +=========== ========== ============== ========================================================== +Clock Cycle Field Name Field contents Comments +=========== ========== ============== ========================================================== +1 START 1101/1110 1101 for READ, 1110 for WRITE. +2 IDSEL 0000 to 1111 IDSEL value to be shifted out to the chip. +3-9 IMADDR YYYY The address to be read/written. 7 cycles total == 28 bits. +10+ ... ... ... +=========== ========== ============== ========================================================== + +LPC + +=========== =================== ============== ========================================================== +Clock Cycle Field Name Field contents Comments +=========== =================== ============== ========================================================== +1 START 0000 ... +2 CYCLETYPE+DIRECTION 010X/011X 010X for READ, 011X for WRITE. X means "reserved". +3-10 ADDRESS YYYY The address to be read/written. 8 cycles total == 32 bits. +11+ ... ... ... +=========== =================== ============== ========================================================== + +Generally, a parallel flash chip will not speak any other protocols. +SPI flash chips also don't speak any other protocols. +LPC flash chips sometimes speak FWH as well and vice versa, +but they will not speak any protocols besides LPC/FWH. + +Hardware Redundancy +=================== +Gigabyte's DualBios: http://www.google.com/patents/US6892323 + +ASUS: http://www.google.com/patents/US8015449
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Anastasia Klimchuk (Code Review)