This package contains the following files:

README        - You are reading it
SSS_ROM.pdf    - Schematic of the original SSS ROM cartridge
SSSROM1.bin - 16 bit image of the entire ROM.
SSS_MS.bin - 8 bit ROM image of the high byte suitable for use with 8K EPROMs
SSS_LS.bin  - 8 bit ROM image of the low byte suitable for use with 8K EPROMs
PROM.bin - contents of PROM used for address decoding only 64 words in the PROM are actully used 
PROM.txt  - file that shows the relation between system address and PROM locations and content.
Chip_Guide.jpg - Photograph of the top of the original SSS ROM.

Note that I have omitted the decoupleing capacitors on the schematics, see photograph of the top of card for placement of bypass caps.

There is not a lot to say about this ROM project.  The ROM itself is an enhanced version of the HP 98228A Mass Storage.  The manual for this ROM was previously up loaded to the HP9825/Structured Software Systems directory by Jack Rubin.  I obtained one of these ROMs from Jack in exchange for doing some repair work for him.  There are no custom parts used in this ROM module save a 82S129 256x4 PROM that is used to decode addresses.  Only 2 bits in 64 locations within the PROM are actually used.   There are some other substitute PROM blanks that are easier to find and you can even substitute PROM of different  layouts.  When I wire-wrapped up a test card to verify that my schematic was correct  I actually used a 256x8 PROM that I had harvested from somewhere and I found that the top half of the PROM was blank, so I tied the 2 most significant address bits high and used two bit of the top 64 words in the PROM.  You will see  in the picture that SSS  used 74HC373 chips to latch the address, 74LS373 work just as well, also you can substitute a 74LS32 for the 74ALS32.  The 74ALS1000 is a driver version of the 74ALS00, a 74LS00 work just fine. 