SIMCHECK II SUPPORT FOR BUFFERED AND UNBUFFERED 168-PIN DIMM MODULES

The 8-BYTE 168-pin DIMMs are now more popular than SIMMs due to the DIMMs' strong advantage in packaging high-density memory arrays on smaller boards.

The original 168-pin DIMM modules are called BUFFERED DIMMs because they use buffer logic chips on their control lines to reduce loading on the motherboard. This buffering action increases the maximum number of modules on the same motherboard. The buffered DIMMs come with standard DRAM chips for either 5V or 3.3V operation.

Recently, IBM and others have developed the UNBUFFERED version of the standard DRAM DIMMs. The UNBUFFERED DIMMs do not use any buffer logic chips, thus achieving faster operation due to the elimination of the propagation delay of the logic buffer. This increase in speed comes at the cost of reducing the maximum number of modules on the same motherboard.

This application note outlines INNOVENTIONS solutions for testing standard BUFFERED and UNBUFFERED DIMMs on the SIMCHECK II and SIMCHECK PLUS systems. Other application notes will describe our solutions for the new 144-pin SO DIMMs and the Synchronous DRAM 168-pin DIMMs.

DIMMCHECK 168P PRO

The new DIMMCHECK 168P PRO (p/n INN-8484-10) is a universal 168 pin DIMM adapter which test most BUFFERED and UNBUFFERED 3.3V or 5V standard DRAM DIMMs. This adapter benefits most volume test requirements as it features a quality YAMAICHI test socket with easy DIMM insertion and removal.

LOW COST DIMMCHECK 168P FOR SPECIFIC DIMM TYPES

Customers who test low quantities of DIMMs per month, mostly of one type, may choose to use our low cost DIMMCHECK 168P, which uses a smaller production type socket with key locks for a specific combination of buffered or unbuffered and 3.3V or 5V.

We now offer three flavors of DIMMCHECK 168P:

• DIMMCHECK 168P for 5V BUFFERED DIMMs (used in Apple computer machines) - p/n INN-8484-9.
• DIMMCHECK 168P for 3.3V UNBUFFERED DIMMs (used in IBM machines) - p/n INN-8484-9-3VUB.
• DIMMCHECK 168P for 3.3V BUFFERED DIMMs (a less popular combination which exist in the market) - p/n INN-8484-9-3V.

IDENTIFICATION OF 168-pin DIMM TYPES

The DIMMCHECK 168P PRO and the DIMMCHECK 168P share the same software and will automatically detect if the DIMM under test is buffered or unbuffered. However, the following discussion will enable you to inspect the DIMM modules you currently have and determine their type before ordering a specific DIMMCHECK 168P. Please note again that the DIMMCHECK 168P PRO is a universal solution for both buffered and unbuffered, 3.3V and 5V standard DRAM DIMMs.

You can tell that a DIMM is buffered if you see the buffer logic chips which are usually marked 74FCT16244 or 74ABT16244 or similar number. The unbuffered DIMM does not have the buffer logic chips. Instead, the unbuffered DIMM has a small, 8-pin serial EEPROM (usually marked 24C02) which contains 128 byte module information (a lot more information compared to the simple 10 presence detect map of the buffered DIMM).

The best way to determine the type and voltage of your DIMM is to inspect the two key positions on the module. The keys are small tabs which correspond to specific lock keys in the motherboard sockets. The socket keys prohibit the insertion of wrong type DIMM modules in a given socket.

All key locations are determined by their relative positioning to the center of the notch area as seen in the above diagram. The left determines whether the module uses a buffered or unbuffered assembly. The right key determines the voltage requirement. Currently the 5V and 3.3V assignment are the only settings used, however, its expected that a lower setting of 1.5-2.7V will be available in the future. This new voltage requirement will take assignment on the third voltage key setting.

DIMMCHECK 168P PRO and DIMMCHECK 168P PRICE LIST

Back To Home Page