Myri-rules - Guidelines for using the Myrinet LAN

Rev. 1.1 (changes below)

THE SIX COMMANDMENTS OF THE ATOMIC LAN:

NEVER connect or disconect ANYTHING unless you have read and understood these rules.
NEVER plug SW8 or SW8A switches to M2F switches.
NEVER plug SBUS4 host interfaces to M2F switches.
NEVER leave cables dangling off of SW8 switches.
NEVER plug loopback or looped cables to SW8 switches.
NEVER use fast cables with the repeater.

There are three types of equipment in the ATOMIC lab:
- Those which support PECL.
- Those which support LVDS.
- Those which support both PECL and LVDS (Autosense).
In general, switches are one or the other. Old host interfaces are PECL, and the new ones are autosense. One must know which type of equipments can go together.
You can NEVER plug something that is PECL to something that is only LVDS.
Also, the equipments can be classified in two types according to the speed at which they operate:
- FAST:
  - All M2F equipments (M2F-SW8 switch and M2FSBUS32 interface card) are fast when center-pin cable is NOT connected.
  - Fast implies that it supports LVDS.
  - The only LVDS that isn't fast is the repeater, so you can't use the fast cable between repeater and M2F stuff, since the M2F will think "fast", and the repeater will think it is "slow".
- SLOW
  - Slow cables have a center pin connected to ground (shield).

Switches

There are three types of switches in the ATOMIC lab:

M2F-SW8

Myrinet 8-port switch.
No fan.
Supports LVDS ONLY.
Operates at low power.
Can connect loopback.

M2-SW8A

Myrinet 8- port switch.
Has a fan.
Supports PECL ONLY.
Can connect loopback.

SW8

Myrinet 8-port switch.
Has a fan.
Supports PECL ONLY.
If you connect a cable to it, you can't leave the other end open.
When disconnecting a cable from a switch, ALWAYS disconnect it from switch first then from the host.

Network Interface cards

There are three main types of interface cards in the lab:

LANAI 2.3 SBUS4
- Supports PECL ONLY.
- Most hosts on the floor have it, some machines in the lab have it.
- LEDs are down and to the bottom corner of panel (below connector).
- Has 6 socketed PLDs. CPU, ROM are socket mounted on top.
- Old Board.
LANAI 4.1 M2FSBUS32
- Autosense - supports both PECL and LVDS.
- Has one socketed PLD, most other parts are surface mounted.
- New board.
LANAI 4.1 PCI
- Autosense - supports both PECL and LVDS.

Repeaters

Autosense - supports both PECL and LVDS.
Allows to connect anything to anything else i.e. PECL equipment to LVDS equipment.
However, repeater is the only LVDS equipment that isn't fast. So, you can't use the fast cable between repeater and M2F stuff, since the M2F will think "fast", and the repeater will think it is "slow".

Myrinet wires

Myrinet wires operate on two voltage levels:
- PECL
- LVDS
Cables can be classified in two catagories according to their speed:
- Fast Cables:
  - These cables are black ones.
  - Relatively short.
  - Have NO centermost pin (or it is disconnected)
- Slow Cables:
  - Have a centermost pin connected to ground (shield).

Summary of what goes with what

	SW8 (Old)	M2-SW8A (New, Backward comptible)	M2F-SW8 (Newest)	LANAI 2.3 SBUS4 (Old)	LANAI 4.1 M2F-SBUS32 (New)	LANAI 4.1 PCI (New)	Repeater *	Cable free ?
M2-SW8	YES	YES	NO *	YES	YES	YES	YES (F)	NO #
M2-SW8A		YES	NO *	YES	YES	YES	YES *	YES
M2F-SW8			YES(F)	NO *	YES(F)	YES	YES *	YES
LANAI 2.3 SBUS4				YES	YES	YES	YES *	YES
LANAI 4.1 M2F-SBUS32					YES	YES(F)	YES *	YES
LANAI 4.1 PCI						YES(F)	YES *	YES
Repeater *							YES *	YES *

YES - Can be connected.
YES * - Cannot be connected to FAST cables.
YES(F) - Can be connected with FAST cables.
NO */# - Cannot be connected.
NB: Repeaters cannot be connected via FAST cables.

Two types of problems occur when we connect equipments with a (NO) in the corresponding box in the table:

NO * : Fries the host interface, which could be due to one of the following reasons:

Old host interface connected to new switch.
Old switch connected to new switch.
New backward comptible switch connected to new switch.

NO # : Hangs the switch, may fry the switch due to following reason:

When connected to old switch the other end of the cable MUST not be open.

Version History

Version 1.0 - Feb. 1997

Initial version

Version 1.1 - May 1997

Corrected description of FAST vs SLOW cables. Fast cables have NO centerpin; slow have a centerpin connected to ground (sheild).

Description of fast vs. slow
Description of cable types

Updated table to reflect constraint that repeaters CANNOT be used with fast cables

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Last modified May 8, 1997.