Channels ▼

Al Williams

Dr. Dobb's Bloggers


April 08, 2010

It seems that every few years 3D movies make a come back. Creature from the Black Lagoon -- that was the first movie I ever saw in 3D. The last one I saw was Avatar. Quite a difference. Lately there's been talk of 3D ICs -- stacking multiple dice in one package.

A start up company called TierLogic may have an early form of this type of IC available. Its not exactly what most people mean by 3D, but its still a step and a very interesting step at that.

Normal FPGAs work by having RAM memory that stores configuration bits. When the chip powers up, an external source (like a EEPROM) loads the RAM memory and the configuration bits make connections between different parts of the chip. That's an oversimplification, but its close enough.

Where TierLogic differs is that it places the configuration RAM in a layer above the normal FPGA die. That means all of the FPGA die is used for logic and interconnect and none is consumed with configuration RAM.

As an end user, who cares? Presumably a smaller die can have more equivalent gates because of the absence of configuration RAM on the main die (assuming the process to put the RAM layer on doesn't cause too many duds). However, there's another interesting twist if you are producing anything in even moderate volumes. TierLogic can take a device before the RAM is built on top of the die and place in a metal interconnect layer instead.

This gives you a true ASIC very rapidly. Because the underlying FPGA fabric is exactly the same, TierLogic claims that timing and everything else on the new device will be exactly the same regardless of the use of RAM or the use of the metal layer. So--in theory--you can prototype with the TierASIC FPGA and then very easily convert to an ASIC (which requires no configuration and is more tamper-proof than an FPGA).

Related Reading

More Insights

Currently we allow the following HTML tags in comments:

Single tags

These tags can be used alone and don't need an ending tag.

<br> Defines a single line break

<hr> Defines a horizontal line

Matching tags

These require an ending tag - e.g. <i>italic text</i>

<a> Defines an anchor

<b> Defines bold text

<big> Defines big text

<blockquote> Defines a long quotation

<caption> Defines a table caption

<cite> Defines a citation

<code> Defines computer code text

<em> Defines emphasized text

<fieldset> Defines a border around elements in a form

<h1> This is heading 1

<h2> This is heading 2

<h3> This is heading 3

<h4> This is heading 4

<h5> This is heading 5

<h6> This is heading 6

<i> Defines italic text

<p> Defines a paragraph

<pre> Defines preformatted text

<q> Defines a short quotation

<samp> Defines sample computer code text

<small> Defines small text

<span> Defines a section in a document

<s> Defines strikethrough text

<strike> Defines strikethrough text

<strong> Defines strong text

<sub> Defines subscripted text

<sup> Defines superscripted text

<u> Defines underlined text

Dr. Dobb's encourages readers to engage in spirited, healthy debate, including taking us to task. However, Dr. Dobb's moderates all comments posted to our site, and reserves the right to modify or remove any content that it determines to be derogatory, offensive, inflammatory, vulgar, irrelevant/off-topic, racist or obvious marketing or spam. Dr. Dobb's further reserves the right to disable the profile of any commenter participating in said activities.

Disqus Tips To upload an avatar photo, first complete your Disqus profile. | View the list of supported HTML tags you can use to style comments. | Please read our commenting policy.