Browse Prior Art Database

Interleaved Dual-Port VRAM for High-Speed Communication

IP.com Disclosure Number: IPCOM000112026D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Blokkum, D: AUTHOR [+2]

Abstract

Disclosed is the design for a Micro Channel* high-speed communicationr. adapter. This design is capable of running 160 Mbytes on the Micro Channel and a 106-MByte data rate over a fiber-optic cable.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 66% of the total text.

Interleaved Dual-Port VRAM for High-Speed Communication

      Disclosed is the design for a Micro Channel* high-speed
communicationr.  adapter.  This design is capable of running 160
Mbytes on the Micro Channel and a 106-MByte data rate over a
fiber-optic cable.

      Due to the high data rate and the architecture of the Fiber
Channel System a large pool of data buffer was required (4 to 16
MBytes).  The other requirement was that the buffer pool was able to
sustain a 100-Mbyte transfer rate.  Cheap and available DRAM proved
too slow, and fast-time multiplexed SRAM was prohibitive in both cost
and complexity.  Our solution was to use dual-port Video RAM (VRAM).
The VRAM organization was interleaved and ping-pong-buffered.

      Interleaved RAM assures that the access times of the RAM is not
violated.  A word is read every 35 ns into the protocol chip;
interleaving allows every other word to be read every 70 ns, so we
have an even and an odd bank of VRAM.  The interleaving allows us to
use standard grade 70 ns VRAM chips.

      The RAM is dual-ported.  This allows read and write operations
to happen simultaneously.  The Micro Channel can write into the
serial port of the VRAM at a speed of 160 Mbytes/sec.  At the same
time the data can be read at 106 Mbytes on the parallel side of the
VRAM into the FCS protocol chip.

      Data pacing is solved by using ping-pong buffers in the VRAM
organization.  4 Kbytes of data is written into the serial...