IBM 4693 Store Loop Adapter 93F1081
   When installed in a 4693, this adapter communicates with point-of-sale terminals attached to the store loop.

         The PS/2 (R) Store Loop Adapter allows selected IBM PS/2s to act as store controllers when using the IBM 4690 Operating System (4690 OS) Version 1 on IBM's Store Loop Network.  It provides 32KB of non-volatile random access memory (NVRAM) when used in conjunction with 4690 OS Version 1 to ensure that hard file data is correctly written to the disk should a power failure occur.  (older versions exist with 4KB of NVRAM)   The PS/2 Store Loop Adapter card can be used with the IBM 4690 Operating System Version 1 in a retail environment to control a store loop to which can be attached up to 64 IBM 4693 Model 5X1, 4X1, or 3X1 or IBM 4683 Model 001, A01, PX1, or 421 Point of Sale Terminals.  The PS/2 Store Loop Adapter also provides a dump switch that, when used in conjunction with 4690 OS Version 1, provides diagnostic capability so that problem determination can easily be performed.

       If customers are migrating to the IBM 4690 Operating System Version 1, they can continue to use their current PS/2 store loop adapters.  However, these existing adapters support only 4KB of NVRAM.  In some large store environments with high customer throughput, it has been recommended to use two of the 4KB loop adapter cards in the file server controller to increase the performance rate of mirrored writes that can be done in the system. With the new PS/2 Store Loop Adapter being announced today and 4690 OS Version 1, a second loop adapter is not necessary for this environment because the additional NVRAM required to hold records for
multiple mirrored writes is now available on one loop adapter.

When to Use Two 4K NVRAM Loop Cards in the File Server
   There is a limit to the rate of the number of mirrored on update (and/or compound on update) writes that can be made to the same controller (usually the  Master/File Server combination). With GSA and SM the primary file updated in this manner from the  Terminal Sales application is the Transaction Log. As the peak transaction rates approach 4,000 transactions per hour, it is recommended that more CMOS be present to allow for the overlapping of the 'mirrored' updates when several are requested simultaneously. 

     The CMOS holds the record for assurance of data integrity across all the controllers. CMOS is on the loop card and there is only enough CMOS reserved on the first loop card for ONE 'mirrored' update. 

     If there is a second loop card in this Master/File Server controller, then the extra CMOS is used for multiple 'mirrored' updates occurring simultaneously. It allows space for several extra records which allows the acknowledgment to return faster to the application and relieve a possible bottleneck in peak throughput situations.

    SMA (Hardgoods) Release 2.0 running on the LAN may require the second loop card for environments that achieve certain peak sales rates. This would be due to the 'mirrored' updates required by this application.
   Chain Sales has the terminal status file set at 'compound at update'. This will require the second loop  card when sales rates exceed approximately 2,000 transactions per hour.

POS and TR 16/4
   A Token-Ring 16/4 Adapter card and the PS/2 Point of Sale Expansion Adapter can be used with the IBM 4690 Operating System Version 1 in a retail environment to control a Token-Ring Network to which can be attached up to 128 IBM 4693 Model 5X1, 4X1, or 3X1 or IBM 4683 Model 421 Point of Sale Terminals.