Browse Prior Art Database

Move Address Bit From Table to Data

IP.com Disclosure Number: IPCOM000119397D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 1 page(s) / 31K

Publishing Venue

IBM

Related People

Davidson Jr, PS: AUTHOR

Abstract

Disclosed is a way to double the address space of a 16-bit address table so that 17 bit addresses are possible without increasing the memory requirement. The only requirement is that each addressable entry in the data have the first bit of the first two bytes free. The first bit of first byte must always be set to 1 and the first bit of the second byte must always be set to 0.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Move Address Bit From Table to Data

      Disclosed is a way to double the address space of a
16-bit address table so that 17 bit addresses are possible without
increasing the memory requirement.  The only requirement is that each
addressable entry in the data have the first bit of the first two
bytes free.  The first bit of first byte must always be set to 1 and
the first bit of the second byte must always be set to 0.

      In the figure, address table 1 contains a 16-bit address of
'A1E1'x.  This is multiplied by 2 to obtain the 17-bit even address
of '143C2'x, that may or may not be correct.

      The figure shows the two possible cases when the address from
the table is '143C2'x.  In the first case, '143C2'x points to byte 2
that is just before the desired data entry.  Adding 1 to the address,
moves the pointer to byte 3.  Byte 3 has a first bit of 1.  This
value is the lowest order bit of the true 17-bit address, '143C3'x.

      In the second case, '143C2'x points to byte 4 which is the
first byte of the desired data entry.  Adding 1 to the address moves
the pointer to byte 5.  Byte 5 has a first bit of 0.  This value
is the lowest-order bit of the true 17-bit address, '143C2'x.