US 20050080581 A1
In some embodiments, built-in self-test logic is provided for an integrated circuit (IC) device having memory controller logic to generate address and command information for accessing a memory device. Driver circuits are on-chip with the memory controller logic. The driver circuits have outputs that are coupled to on-chip signal pads, respectively. The BIST logic is coupled between the driver circuits and the controller logic. The BIST logic is to transmit, at speed, address and command information that has been generated by the controller logic using the driver circuits in a normal mode of operation for the device. In addition, the BIST logic is able to transmit, at speed, test symbols using the driver circuits in a test mode of operation for the IC device, during which a chip-to-chip connection between the IC device and another device is tested. Other embodiments are also described and claimed.
5. A memory integrated circuit (IC) module, comprising:
a carrier substrate;
a plurality of first and second signal connection points being installed on the substrate;
a plurality of memory devices installed on the substrate, each of which has a separate memory core array and separate address decoder logic; and
a memory buffer installed on the substrate and communicatively coupled between the plurality of first and second signal connection points and the plurality of memory devices,
the buffer having a plurality of driver circuits whose outputs are coupled to the plurality of first signal connection points, respectively, and logic to a) forward read data, provided by the plurality of memory devices, at speed using the plurality of drivers in a normal mode of operation for the module and b) determine error in test symbols received from outside the module at speed using the plurality of second signal connection points in a test mode of operation for the module during which a chip-to-chip connection between the module and another device is tested.
6. The module of
7. The module of
a plurality of third and fourth signal connection points being installed on the substrate; and
wherein the buffer device includes a further plurality of driver circuits whose outputs are coupled to the plurality of third signal connection points, respectively, and further logic to a) forward address and command information, that has been received from outside the module, at speed using the further plurality of driver circuits and b) determine error in test symbols, that have been received from outside the module at speed via the plurality of fourth signal connection points, in a test mode of operation for the module during which a chip-to-chip connection between the module and another device is tested.
8. The module of
9. A system of integrated circuit (IC) devices, comprising:
a carrier substrate;
a host IC device having memory controller logic and being installed on the substrate,
the host IC device having built-in self test (BIST) generator logic coupled between a plurality of driver circuits and the memory controller logic, to a) transmit, at speed, address and command information generated by the controller logic, using the plurality of driver circuits in a normal mode of operation for the IC device and b) transmit, at speed, test symbols, using the plurality of driver circuits in a test mode of operation for the IC device during which an interconnect between the IC device and another device is tested,
the host IC device having BIST checker logic coupled between a plurality of receiver circuits and the memory controller logic, to a) forward data, received by the plurality of receiver circuits, to the memory controller logic in said normal mode of operation for the IC device and b) determine error in test symbols received by the plurality of receiver circuits in a test mode of operation for the IC device during which an interconnect between the IC device and another device is tested; and
a first main memory module being installed on the substrate to communicate with the host IC device,
the first module having a memory buffer circuit with repeater capability to a) forward address and command information from the memory controller logic to a second main memory module, and b) forward read data from the second main memory module to the memory controller logic,
the first module having first BIST checker logic to determine error in the test symbols transmitted by the BIST generator logic of the host IC device.
10. The system of
the second module to re-transmit the test symbols transmitted by the host IC device and forwarded by the first module, back to the first module.
11. The system of
12. The system of
13. The system of
Ser. No. 10/319,517, filed Dec. 16, 2002, entitled “Testing Methodology and Apparatus for Interconnects” (pending); Ser. No. 10/393,223, filed Mar. 20, 2003, entitled “A Reusable, Built-In Self-Test Methodology For Computer Systems”.
Some embodiments of the invention described below are related to methodologies for testing manufactured computer systems, and in particular their main memory subsystems, to determine whether electrical specifications for chip-to-chip connections (also referred to here as interconnects) have been met, as well as whether the integrated circuit (IC) devices in the main memory subsystem have been assembled or installed correctly. Other embodiments are also described and claimed.
Industry trends for high performance computer systems, such as those that use a Pentium processor and associated system chipset by Intel Corp., Santa Clara, Calif., are towards faster product cycle times (time to market) with sustained high quality. At the same time, chip-to-chip connection or bus speeds are increasing to several hundred megahertz and, in the case of serial links, beyond several gigahertz (GHz). Device pin densities are also increasing, again to meet the need for greater performance in the computer system. These demands render conventional testing techniques such as oscilloscope and logic analyzer probing less reliable, and often impossible particularly on high speed interfaces, both in the high volume manufacturing setting, as well as earlier in the electrical validation and verification stage of device and platform manufacturing.
At the board and platform level, the system has its primary components, including the processor, system chipset, and memory, installed on a motherboard. In that stage of manufacturing, transaction-based tests have been used, in a board or platform high volume manufacturing setting, to verify a wide range of storage and logic functions of the system. Such tests evaluate whether the memory subsystem and the I/O subsystem work according to their electrical specifications. The test is performed by the processor executing a special test routine, during or after booting an operating system (OS) program, that causes test patterns that are part of the test routine to be written to and then read from addresses that span the computer system. However, faults of a high frequency type (such as due to cross talk between adjacent signal lines and inter-symbol interference (ISI) due to transmission line effects) cannot be detected or isolated using such techniques, due to the coarse test granularity and high instruction overhead associated with running an OS-based test program.
Another type of computer system test calls for the processor to execute firmware/software that operates at a lower level than an OS-based program, prior to booting the operating system. These include basic I/O system (BIOS) and extended firmware interface (EFI) programs. Although these types of tests provide relatively low-level, and hence more accurate, control of component functionality and interconnect buses, system interactions cannot be stressed to their bandwidth specifications in such tests. In addition, the ability of BIOS/EFI tests to isolate a fault with sufficient granularity is also limited.
Finally, there is a low level technique known as boundary scan testing (or the Joint Test Access Group, JTAG, protocol) which calls for on-chip circuitry used to control individual bits transmitted between components. Once again, however, there is no provision for testing high frequency faults. For example, a boundary scan test may detect “opens” and “shorts” while running at a 10 MHz clock, whereas normal signaling speed on the interconnect will be in the hundreds of MHz or even GHz range.
The invention is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one.
Some embodiments of the invention described below are directed to techniques for enhancing some or all components of a main memory subsystem with built-in self test (BIST) logic circuitry that can test the main memory subsystem. Each enhanced IC component or device has BIST logic that is designed to communicate with other BIST logic, or with initialized components of the subsystem, to determine whether an electrical specification of the subsystem is satisfied or whether the components of the subsystem have been properly installed. The BIST capability here, which may also be referred to as interconnect BIST (IBIST), is capable of testing chip-to-chip connections between IC devices at speed, that is substantially at the same or higher signaling speed (or symbol rate) as that used in a normal mode of operation for the subsystem. The IBIST logic also has a transparent, or also referred to as “normal”, mode in which the IC device involved can operate to perform its primary memory-related function, e.g., to transmit address and command information and/or data that are typically needed for accessing the subsystem. According to an embodiment of the invention, the IBIST capability relies upon design for test (DFT) on-chip logic to establish test conditions and test symbols, execute a test of the interconnect, and return results of the test to, for example, an on-board platform management system or to an external tester. With IBIST, the memory subsystem can in effect test itself for defects and verify the high speed performance of chip-to-chip connections in the subsystem at the platform level, high volume manufacturing stage (for example, computer system printed wiring board manufacturing). In other embodiments, the IBIST capability in a device can self-test its IC package connections to a test board, at the IC device validation stage or later during volume manufacturing of the IC package.
Referring now to
The IBIST logic 108 is positioned between the driver circuits 113 and receiver circuits 115 on one side and memory controller (MC) logic 120 on the other. The MC logic 120 provides address and command information for accessing a memory device (not shown), to the IBIST logic 108. In response, the IBIST logic 108 transmits, at speed, this address and command information using the driver circuits 113, in a normal or transparent mode of operation for the IC device 104. In contrast, in a test mode of operation for the IC device 104, the IBIST logic 108 may be configured as a test master that transmits, once again at speed, test symbols using the driver circuits 113. The test mode of operation is one during which a chip-to-chip connection between the IC device 104 and another device is tested.
The die signal pads 114 and receiver circuits 115 allow bi-directional communications with another device. To support that capability, the IBIST logic 108 includes further logic coupled between the receive circuits 115 and the MC logic 120 to forward data, received by the receiver circuits 115, to the MC logic 120 in the normal mode of operation for the device 104. For example, this data may be the contents of memory locations read from a memory device. On the other hand, in the test mode of operation, the IBIST logic 108 may be configured to act as a test slave which automatically determines error in test symbols that have been received by the receiver circuits 115. This automatic “checking” ability can be extended to some or all of the die signal pads 114 of the IC device 104 that are part of the chip-to-chip connection being tested.
Information regarding the determined errors, if any, by the IBIST logic 108 may be transferred out of the IC device 104 via a test access port (TAP) 124. The TAP 124 is coupled to a separate die pad 128 used for transferring the results of testing performed by the IBIST logic 108. The pad 128 may in some cases be also used for loading the IBIST logic 108 with a pattern of test symbols that are driven and checked by the IBIST logic 108 when performing an interconnect test of the chip-to-chip connection. The IBIST logic 108 and the TAP 124 may be designed to have boundary scan chain capability, to scan in test pattern information and scan out the error information according to conventional boundary scan chain techniques used for testing multiple chain linked devices in a computer system board. As an alternative, any error information and/or test pattern information may be transferred to and from the IC device 104 via internal registers (not shown) that are accessible by either a separate low speed test bus such as the System Management Bus (SMBUS) (not shown) or are mapped into the central processing unit (CPU) I/O addressing space of the computer system.
Turning now to
Each memory module 204 is made of a carrier substrate 214 (such as a separate, printed wiring board with multiple signal routing layers as used for conventional dual in-line memory modules or DIMMs). A number of memory devices 222 and multiple sets of connection points 216-219 are installed (e.g., directly soldered) on the substrate 214. There are in this case four sets of connection points 216-219 that are installed on the carrier substrate 214, where each set supports multiple electrical signals, and that form the transmission line between the modules 204 and the host IC device 104. In a computer system embodiment, the links 208 and 209 are formed in a mother board or system board (not shown) through which metal traces and connector slots that constitute the links 208, 209 are provided. Other types of connections for allowing the modules 204 to communicate with each other and with the host IC device 104 may be possible.
Each module 204 further includes a number of memory devices 222 that are communicatively installed on the carrier substrate 214 (e.g., soldered). Each memory device 222 has a separate memory core array and separate address decoder logic (not shown) to store the data and provide access to it. These memory devices may be solid state, volatile or non-volatile devices such as dynamic random access memory (DRAM) devices. Each memory device may be a packaged set of one or more IC chips, where each chip has a separate memory core array and separate address decoder logic. Other ways of packaging a memory device may be used.
The memory devices 222 are communicatively coupled to a memory buffer 220 that is also installed on the substrate. Multi-drop command/address and data buses are tapped into by in this case several memory devices 222_1, 222_2, . . . 222_M to communicate with the memory buffer 220. Other configurations for connecting multiple memory devices to a memory buffer are also possible.
The memory buffer 220 is to decode local memory command, address, and data (that is, intended for one or more of the memory devices 222 that are located on the module 204_1 rather than memory devices that are located on other modules). The memory buffer 220 is designed to improve memory operation by “re-driving” the address, command and data signals. The memory buffer 220 may be external to the module 204 or it can be located on the module 204 as shown in the embodiment of
Note that the data that arrives at the memory buffer 220 may be synchronized to a system reference clock, so that the clock used to detect symbols is referred to as a derived clock. As an alternative, the buffer 220 can provide a reference clock along with the transmitted (or re-driven) data—this being referred to as a forwarded clock. Yet another alternative is where the clock is embedded in the data signal, also known as embedded clock.
The memory buffer 220 may be built using a fabrication process that is different than one which is optimized for making memory devices such as DRAM devices. This allows the memory buffer 220 to be enhanced with IBIST logic more cost-efficiently than integrating the IBIST logic in the memory devices 222. The IBIST logic in the memory buffer 220 is categorized as being of two types, BIST generator and BIST checker. Their capabilities will be described below.
Still referring to
A module's interface with other modules of the memory subsystem is now described. Using the memory module 204_1 as an example, the module is enhanced with further logic that is designed to test a chip-to-chip connection between the module 204_1 and its adjacent module 204_2 (not shown). This connection to be tested includes an inbound link 209_2, connection points 219, and receiver circuitry (not shown) of the memory buffer 220. To perform such a task, test symbols are transmitted by the memory buffer 220 via the connection points 218 and outbound link 208_2. One of the memory modules that are further downstream, that is for instance module 204_2 or subsequent ones, is configured or programmed to loop these test symbols back towards the host IC device 104 via some internal loop back path (shown as a thick dotted line in
It should be noted that in the above-described embodiment, the test symbols originated with a BIST generator 225 located in the host IC device 104, and were then forwarded by the module 204_1. An alternative implementation is to add a BIST generator (not shown) to the memory buffer 220 of a module, to originate the test symbols. This alternative embodiment allows a module to in effect test itself, for example the connections that include the connection points 218, outbound link 208_2, inbound link 209_2 and connection points 219. In addition, the connections composed of inbound link 209_1, connection points 216, outbound link 208_1 and connection points 217 can also be tested, using an additional BIST generator (not shown). In that case, the test symbols transmitted by the module 204_1 would need to be looped back towards the module 204_1 through some external mechanism such as a simple wire loop or a form of repeater circuitry. The module 204_1 as a whole, or its memory buffer 220 by itself, may be installed on a test board, for either validation self-test or volume manufacturing self-test for which a loop-back has been provided on the test board.
The main memory subsystem depicted in
Referring now to
At the receiver end, receiver circuitry 360 translates the incoming transmission line signal into a serial bit stream that is converted into parallel symbols by a de-serializer 356. The differential input to the receiver circuit 360 may be directly connected to a single link 208_1 or 209_2 of the module 204 (see
As part of the IBIST logic, multiplexers 316 and 344 are added, to provide an additional path for test symbols to be received (multiplexer 344) and transmitted (multiplexer 316) in a test mode of operation. For multiplexer 316, an additional loop back path from the elastic block 348 is provided, so that received test symbols can be looped back, as was discussed above in connection with
As shown in
Turning now to
Next, operation may proceed with block 408 in which the IBIST logic of the components of the main memory subsystem, and optionally the host IC device, are programmed to establish a test pattern to use as well as which chip-to-chip connections to test. Thus, for example, referring now to
Next, operation proceeds with block 412 in which the IBIST logic units are instructed to start a test session, with a test master transmitting test symbols over a predefined chip-to-chip communications connection of the subsystem. In the embodiment of
Operation then proceeds with block 416 in which the test symbols, that were transmitted at speed, are received and checked against a test symbol pattern that is stored in a first memory module of the system. These received test symbols are then looped in the first module, back to the host IC device over an inbound chip-to-chip communications connection of the system that is normally used by the first module to send read data at speed to the host IC device. Thus, for the embodiment of
To summarize, various embodiments of a built-in self test methodology for computer systems have been described. In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. For example, the reference to a “computer system” is not intended to be limited to general purpose (e.g. personal) computers but rather encompasses any digital system board or platform that could benefit from the above described main memory subsystem test methodology. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.