Digital (Was RE: Mac "Workgroup Server" (or "network server") hardware & AIX)

Jon Elson elson at
Wed Apr 27 22:10:27 CDT 2016

On 04/27/2016 09:34 PM, Eric Smith wrote:
> On Wed, Apr 27, 2016 at 7:09 PM, Jon Elson <elson at> wrote:
>> Sure.  A VAX 11/780 had a 5 MHz clock!  Would be hard for an emulator to NOT
>> beat that!  Later models did run faster, but not vastly faster, due to the
>> technology of the time.
> I'm not sure what would qualify as "vastly faster", but I take it that
> 170.9 MHz doesn't?
> (also required fewer clocks per instruction than the 11/780)
Well, running an efficient simulator on a modern PC 
processor with a 3+ GHz clock, with faster memory and larger 
and faster cache, I think it would still beat that top/end 
of the line VAX.  But, I don't actually know for sure.
> A well-tuned VAX design in a recent FPGA family (Xilinx 7-series or
> newer, or Altera Stratix V or newer) might be able to outperform the
> fastest "real" VAX, but perhaps not by a whole lot.  FPGAs are
> generally much more efficient at implementing RISC processors, but
> it's difficult to get a whole lot more than 200 MHz for the
> cost-optimized FPGAs, or 350 MHz for the (expensive)
> performance-optimized FPGAs.
> I've designed VHDL cores equivalent to microprocessors such as the RCA
> 1802, National Semiconductor PACE, and DEC/Western Digital LSI-11 (at
> the microarchitecture level). I'd like to tackle something more
> sophisticated, but it's hard to find enough time.
Wow, yeah, designing a hardware emulator on an FPGA for the 
VAX would be a big project.  Doing the same for the Alpha 
architecture would be REALLY daunting, since a lot less was 
done by microcode.


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