July 2nd, 2017 ~ by admin

ITT AN/ALQ-136 Countermeasures Processor – Bit Slice with a Bite

ITT 80063SM-A-919797 – AN/ALQ-136(V)I Processor. The 2901B’s are the 4 larger dies in a row, middle right.

Military computing applications require many custom designs, as they are very mission specific.  A great example is this ITT hybrid processor.  It was designed and used for the AN/ALQ-136(V)1 CMS (CounterMeasures System) for the AH-1F Cobra Attack helicopter.  Two of these hybrids are used in the system, one for the Mod Recovery board, and one for the SLO processor board.  These boards are used to detect hostile pulse RADAR systems, analyze them, and begin jamming based on what type they are.

This requires relatively fast processing, and a generally custom design.  Today a modern DSP processor could handle this task without issue.  However in the early 80’s (the AN/ALQ-136 debuted in 1982) DSP processors were in their infancy.  In 1982 a fast custom processor needed to be built with bit-slice elements.  In this case the very versatile AMD 2901 was used.  The ITT hybrid integrates 4 AMD AM2901B processor dies, as well as associated memory and interfacing elements.  The single package contains almost 100 dies, and many discrete components.  It is built on a ceramic substrate with gold traces, and sealed in a metal package.  This is required to protect the digital components of the system from electronic interference, whether from external sources, or from the helicopters own RADAR systems.  The AN/ALQ-136 is designed to prevent the Cobra from being successfully targeted by RADAR guided missiles, failure means a strong possibility that the helicopter gets hit, not something its crew would like to deal with.

4x AMD AM2901B Dies.

The 4 AMD 2901Bs run at 16MHz (50% faster then the original 2901s) and are made with ECL; together they provide 16-bit processing of the incoming RADAR signals. The SLO (Side Lobe Opposition) and MOD Recovery (Modulation Recovery) are used to determine the exact type of the enemy RADAR.  Each RADAR has a distinct characteristic that the CMS can match and respond to.  The CMS is programmed to respond to the radar signals of the most critical threat weapon systems anticipated to be encoun

Israeli AH-1F Cobras – Now Retired/Transferred to Jordan.

tered in the hostile environment.  These signatures are stored in the hybrids ROMs as well as the desired response to them.  Updates likely remain replacing these hybrids with updated versions.  New countermeasures systems (such as the 136’s replacement, the AN/ALQ-211) are more easily upgradeable to new threats.

The AH-1F Cobra continues to fly with the air forces of several countries around the world, notably Pakistan, Jordan, and Turkey.  The United States Forest Service also operates 25 AH-1F Cobras for wildland fire use, but it is rather unlikely that the countermeasures on these are operable, let alone needed.

June 2nd, 2015 ~ by admin

MG80386SX: Pin counts: How low can you go?

Intel MG80386SX16 in a 88-pin PGA

Intel MG80386SX16 in a 88-pin PGA

Seeing this pin out, the first processor that comes to mind probably isn’t an Intel 80386.  The 80386DX came in a 132 pin package (PGA or QFP) and the 386SX came in a 100 pin QFP.  The 386SX was the low end version of the 386.  It made do with 16 bits of Data bus, and 24 bits of Address, as opposed to the full 32-bit buses of the DX.  This accounts for 27 less pins (16 Data + 7 Address, 2 data byte selects and a 16/32 bit pin).  That covers all but 6 of the difference in package sizes.  Where are the rest from?  As with most processors, the signaling pins are not the only pins used, or not used on a package.

The 80386DX has 84 signal pins, pins that carry information to or from the processor.  It also has 40 pins for power and ground.  In the early days, when processors had only 40 pins or less, it made sense, and was feasible to have a single power and ground for the entire chip.  As complexities increased, routing became harder, and it became easier to have multiple power and ground pins to the die.  Not to mention electrically more stable, as current requirements were also increasing.  In addition the 386DX has 8 pins not used at all.  These are known as ‘No Connects.’  They are reserved for future use, or were there for testing, or simply just not needed.

Intel 5962-9453301MXA MG80386SX16 - 16MHz 80386SX - 1996 Full Milspec

Intel 5962-9453301MXA MG80386SX16 – 16MHz 80386SX – 1996 Full Milspec

Moving to the 386SX, which has 26 less signal pins (58), the standard 100 pin package used 10 No Connects and the rest (32) for power and ground.  The pictured 386SX is a late production (1996) military spec processor in an 88 pin package.  88 pins still leave plenty (30 pins) for power, ground, and no connects.  The PGA 386SX was only produced for military/industrial uses.

Why use an expensive PGA package on a low end SX processor?  The reduced bus sizes were plenty for many industrial applications while the ceramic package was much more reliable, and mechanically strong when soldered on to a board then a plastic QFP.  The PGA could work over the entire military specification, for temperature, voltage etc.  Its likely the 386SX could run on an even smaller pin count, but the PGA88 package was a standard package already in production, which often dictates how many pins a processor will have.  The same is true today, pin-count is usually driven more by what works for the package, then what the processor actually strictly needs.