[fpc-devel] Improving i8086 performance..

Jim Leonard trixter at oldskool.org
Mon Dec 23 17:27:50 CET 2013

On 12/23/2013 7:34 AM, Max Nazhalov wrote:
> Hello, Everybody!
> Can anyone having the real i8086 hardware check attached MUL-helpers?
> I've tested them on a modern Intel CPU -- "mul_dword" is about 4.5..5
> times faster comparing to the generic FPC implementation, and
> "mul_qword" is about 18..20, but these numbers surely should be quite
> different for the real i8086 due to the progress in the today's ALU design.
> Just curious how "fast" they can be in the silicon of those days..

I'm not sure how useful a comparison this is because there is no dword 
or qword MUL on i8086.  Also, your request is not clear:  Do you want 
them checked for correctness, or speed?

Do you need a real 8086 or will an 8088 do?  I have both, but the 8088 
is set up right now whereas I'd need to drag out the 8086 and set it up. 
  But in either case, I won't write your test harness for you; if you 
provide me with a compiled harness .exe then I'd be happy to run it for 
you and send you the results back.

If you don't know how to write a harness with decent timing code, just 
print the system time, do 1000 iterations, then print system time again. 
  808x is slow enough that 1000 iterations will be enough to get good 
Jim Leonard (trixter at oldskool.org)
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