Cache RAM snoops system bus
The MK45180 SnoopTag cache RAM integrates bus-snooping logic along with a
4-K x 10-bit asynchronous dual-port RAM. The local port connects to the
local processor's address bus and performs TagRAM functions in the usual
way. The other port, called snoop port, monitors the system bus. The
snoop logic uses the 12-bit snoop index and 10-bit tag data to detect
writes to main memory that would invalidate data in the local cache.
Because the RAM is dual port, the tag function's address-to-match time of
20 ns is always available. Collision-detection logic raises a flag if the
local processor attempts to write to a location that is simultaneously
being invalidated by the snoop logic. The chips can be paired for 20-bit
tags. The vendor also offers the MK62486, a 32-K x 9-bit burst-filling
cache RAM for 80486 systems. (MK45180, $29.33 ea/5,000; MK62486-19, $13.29
ea/5,000–available now.) SGS Thomson Microelectronics Phoenix, AZ
Marketing 602-867-6259 Fax 602-867-6102
Advertisement
