FPGA VAX update / cool microcode evolution

[Jim Battle]

Sridhar Ayengar wrote:

> Steve Thatcher wrote:
> 
>> and I don't need to hear your profanity about technology that you do 
>> not care to use. Others don't seem to have a swear to "talk" and they 
>> don't seem to have a problem using whatever software tools are 
>> necessary to get the job done.
> 
> 
> Great.  Foist your Puritanical Western Judeo-Christian ideals on the 
> rest of us.

Sridar, you are jumping to conclusions.  I agree with Steve, and I'm an atheist. 
  Certain people don't seem to understand that the thing about swear words is 
that their power derives from their infrequent use.  Use them too often (once a 
sentence for certain posters) and they are just obnoxious filler.

Getting back on topic, here is an interesting old computer tidbit.

Wang started shipping their 2200 family of computers in 1972.  The first 
generation used a 4b ALU and a lot of microcode.  The next generation, circa 
1976, used an 8b ALU, a more powerful microcode instruction set, and ran 8x 
faster overall.  Then Wang put more emphasis on their VS family, and the 2200 
languished.  In the early 80s they reduced the CPU to a single VLSI chip, 
although it ran at the same speed as the logic it replaced.

In the late 80s there was still pressure from customers to continue and extend 
the 2200 family, but Wang apparently didn't want to commit the resources to a 
whole new CPU design, nor to port their sprawling BASIC-2 to an existing processor.

Now, getting to the interesting part: Wang solved this problem around 89 by 
coming out with a CPU card upgrade -- it consisted of a 16 MHz 386 and a binary 
translator that converted 2nd generation microcode to x86 instructions!  Just 
swap the CPU, keep all peripherals and chassis and you get an immediate 2x speed 
improvement.  Although there was a slight startup cost when microcode was 
loaded, translation could be done statically due to the simple nature of the 
microcode.  A short time later they came out with a 33 MHz 386, doubling the 
speed again.

If they had kept upgrading their technology, a 2 GHz CPU today would make that 
BASIC 250x faster than the VLSI version.

In comparison, my not so agressively optimized 2200 emulator is only about 15x 
faster at the same 2 GHz clock rate, as it uses straight-forward cycle-by-cycle 
microcode interpretation.