Santa Clara, Calif.We recently looked at a new FB-DIMM (Fully Buffered DIMM) tester from Tektronix.
Another company has also joined the FB-DIMM test fray, namely Pycon, Inc. Actually predating Tek's announcement, Pycon has shipped more than 130 FB-DIMM testers since November of last year.
A word about FB-DIMM. Extending conventional DDR2 (double data rate 2) technology, FB-DIMM features memory modules that are similar in size and appearance to today's DIMM modules. However, FB-DIMMs take up significantly less board space than parallel interfaces. Lead-in lengths of up to 12 inches, relaxed trace length matching, and support for repeaters can also ease system design.
Electrically, the technology's architecture interposes an intelligent buffer device between a host's memory controller and DRAM. The FB-DIMM channelized architecture places high-speed serial point-to-point interconnections between the memory controller and the first module, and between subsequent modules on a channel.
The result is that FB-DIMM offers practical main-board memory capacities of up to 192-Gbytes using six channels, with eight DIMMs/channel, and two ranks/DIMM of 1-Gbit x 4 DRAM.
In operation, FB-DIMM is expected to support 6.4-Gbyte/s sustained data throughput speed per channel. With four channels and DDR2-800 DRAMs, a system would have a whopping 25.6-Gbyte/s throughput rate.
FB-DIMM also offers CRC (cyclical redundancy checking) protection for both commands and data, with bit lane fail-over and transient error detection and retry. That very strong CRC provides a failure rate of less than one failure per million years per channel segment.
Enter Pycon's tester. Priced at about $4500, it does link testing using a technique Pycon calls IBIST (interconnect BIST). IBIST supports on-die pattern generators and checkers that test a link at full speed. IBIST self-test also permits buffer I/O verification at the buffer or DIMM level.
IBIST also supports host-to-buffer and buffer-to-buffer testing, which is used to test connections between DIMMs. Using Pycon's IBIST, errors can be isolated to specific segments and lanes on an FB-DIMM channel, speeding failure analysis and repair.
Pycon's tester also supports DRAM testing. Its MemBIST function tests DRAM behind the buffer at full speed of DDR2 DRAM. In a system, MemBIST can test and zero many DIMMs at the same time, too. At the DIMM level MemBIST can detect DIMM assembly defects, and other defects, too.
Pycon's system also supports DIMM manufacturing test using a so-called transparent mode. It gives access to the DRAM, controlling address and data to be applied. In use, FB-DIMM I/O is configured for lower speed (typically corresponding to DDR2-400 timing).
What's more, existing DDR2 DIMM tests can be converted to FB-DIMM transparent mode, protecting investments in DRAM and DIMM test development.
For observability testing, Pycon offers an LAI (logic analyzer interface) mode. LAI Mode is an optional feature that permits observation of FB-DIMM channel traffic.
In use, the FB-DIMM buffer has functions that permit signal observation on conventional equipment. In fact, high-speed FB-DIMM signals can be observed and captured in realtime.
The system's CTC (channel test card), designed by Intel, is an FB-DIMM memory channel with standard routing and stackup, but without a host controller. The CTC has slots for one virtual host and eight FB-DIMM modules. The CTC lets you do evaluation of real-world FB-DIMM traffic.
Tests will be portable to platforms using a CTC API (application programming interface). This supports rapid evaluation of FB-DIMM in a system-like environment, with an upgrade path to real systems when they become available.
FB-DIMM DFT (design for test) features are also available on the CTC, supporting evaluation of real-world FB-DIMM traffic and test cases without the usual need to wait for development of a supporting platform. It's significant that Intel is developing documentation, software, and example tests for the CTC right now, however.
The CTC also packs an on-board USB (Universal Serial Bus) to SMBus (System Management Bus) converter, a programmable reference clock, four on-board programmable power supplies, and one 3.3-V fixed-voltage power supply.
All CTC functions and AMB (Advanced Memory Buffer) control and status registers can be accessed via the USB interface, using application software that can run on any Windows computer.
Note that Pycon is offering volume discounting for its tester, and even has an enticing introductory price of $3500 for the first two units you purchase.
For more info, contact Rob Ortega at Pycon Inc., 3301 Leonard Court, Santa Clara, Calif. 95054. Phone: (408) 727-1213, or (408) 450-5609. Fax: (408) 727-2670. E-mail: email@example.com.
Check out Pycon's Web site for related information.