Browse Prior Art Database

Main Store Tags Register

IP.com Disclosure Number: IPCOM000101909D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Imming, KC: AUTHOR [+3]

Abstract

Disclosed is hardware implementation of the Main Store Tag Pointers for a processor. Previously, tag insertion into main store and extraction from main store has been handled by horizontal microcode. Much of this function can now be performed by the hardware.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Main Store Tags Register

       Disclosed is hardware implementation of the Main Store
Tag Pointers for a processor.  Previously, tag insertion into main
store and extraction from main store has been handled by horizontal
microcode.  Much of this function can now be performed by the
hardware.

      The processor architecture provides tag bits in main store to
protect quad word pointer values within the main store.  Only a
limited set of instructions is allowed to manipulate the pointer
values.  Any other instructions attempting to modify a pointer will
cause the tag bit to be set 'off'.  This protection mechanism
prevents illegal modification of these pointer values.

      Logically, there is one Tag bit per quad word of main store
data.  Physically, this is implemented as one Tag bit per full word
of main store data.  This is required since the main store card can
alter data in a single full word, and must be able to reset the Tag
bit if this occurs.  The Tag bit is 'on' only if all four (of the
full word Tags) in main store are set.

      To swap a page (512 bytes) of main store data out to DASD
(direct access storage device), the tag bits must be accumulated
(extracted from main store) into one 32-bit value (512 bytes = 32
quad words).  Likewise, to swap in a page of main store data from
DASD, the 32 tag bits must be distributed (inserted) back into the
main store page.

      Each of the new tag instructions can insert or extract tags
from up to 256 bytes of main store data (16 tags, 1 tag per quad
word).

     ...