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Die shrink of a processor I worked on in the 90's, the C-Cube CL4010. Looks like the design changed even though it was functionally equivalent. http://www.w6r

by drmpeg 6y ago

Die shrink of a processor I worked on in the 90's, the C-Cube CL4010. Looks like the design changed even though it was functionally equivalent. http://www.w6rz.net/IMG_0044.JPG http://www.w6rz.net/IMG_0044.JPG

to11mtm 6y ago
Maybe to help manufacturing yield improvements? Sometimes a design change can improve part yield, and if you're already having to validate it for a die shrink anyway, it might be worth the cost of a redesign. Especially if the chip is composed of IP Blocks (or a similar analogue.)
monocasa 6y ago
That's really neat! Was there ever public documentation on the microarchitecture of these chips? I seem to remember them from back in their day and it'd be neat to see how they worked.
- drmpeg 6y ago
  Unfortunately, this was around 1993-1995 and PDF's weren't in widespread use yet. Everything was on hard copy and I'm sure I tossed that years ago. It was a fully custom 32-bit ISA and we had a custom back-end for GCC (although a lot of the code was written in assembly language). The I-cache was manually loaded. The C compiler had a mechanism to detect when the instruction pointer went off the ends of the current I-cache page and automatically loaded the target page. I can't remember if it was some sort of trap or if it was hard-wired in the code. The chip had some specialized processing units, most notably a motion estimation engine that did billions of MSE operations per second and a DSP engine for the DCT/IDCT. The chip was used for the DirecTV roll-out in 1995. I remember watching the OJ Simpson chase on a test receiver in the lab at C-Cube. The original DirecTV encoders used the CL4000 and were actually MPEG-1 at 720x480 resolution. They used 8 chips to parallel process the image in strips. When the CL4010 was ready, the encoders were upgraded to MPEG-2 with a 12 chip architecture (4 chips added to do the additional field/frame motion estimation).
  - monocasa 6y ago
    Neat! Thanks so much for the run down!
djmips 6y ago
Are you sure the design changed and it's not just the way light is playing off the surface at the different sizes?

by drmpeg 6y ago

to11mtm 6y ago

Maybe to help manufacturing yield improvements? Sometimes a design change can improve part yield, and if you're already having to validate it for a die shrink anyway, it might be worth the cost of a redesign. Especially if the chip is composed of IP Blocks (or a similar analogue.)

monocasa 6y ago

That's really neat! Was there ever public documentation on the microarchitecture of these chips? I seem to remember them from back in their day and it'd be neat to see how they worked.

drmpeg 6y ago
Unfortunately, this was around 1993-1995 and PDF's weren't in widespread use yet. Everything was on hard copy and I'm sure I tossed that years ago. It was a fully custom 32-bit ISA and we had a custom back-end for GCC (although a lot of the code was written in assembly language). The I-cache was manually loaded. The C compiler had a mechanism to detect when the instruction pointer went off the ends of the current I-cache page and automatically loaded the target page. I can't remember if it was some sort of trap or if it was hard-wired in the code. The chip had some specialized processing units, most notably a motion estimation engine that did billions of MSE operations per second and a DSP engine for the DCT/IDCT. The chip was used for the DirecTV roll-out in 1995. I remember watching the OJ Simpson chase on a test receiver in the lab at C-Cube. The original DirecTV encoders used the CL4000 and were actually MPEG-1 at 720x480 resolution. They used 8 chips to parallel process the image in strips. When the CL4010 was ready, the encoders were upgraded to MPEG-2 with a 12 chip architecture (4 chips added to do the additional field/frame motion estimation).
- monocasa 6y ago
  Neat! Thanks so much for the run down!

djmips 6y ago

Are you sure the design changed and it's not just the way light is playing off the surface at the different sizes?