[fpc-devel] Improving i8086 performance..

Kostas Michalopoulos badsectoracula at gmail.com
Fri Dec 27 16:35:12 CET 2013

If you want to do speed tests, try some emulator. For example PicoXT
(which emulates an XT clone):

On Mon, Dec 23, 2013 at 5:27 PM, Jim Leonard <trixter at oldskool.org> wrote:
> 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 numbers.
> --
> Jim Leonard (trixter at oldskool.org)
> Check out some trippy MindCandy: http://www.mindcandydvd.com/
> A child borne of the home computer wars: http://trixter.oldskool.org/
> You're all insane and trying to steal my magic bag!
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