Mail Archives: djgpp/2000/03/13/10:12:47
On 12 Mar 2000 16:31:25 -0800, Nate Eldredge <neldredge AT hmc DOT edu>
wrote:
>Damian Yerrick <DONT DOT YOU DOT DAREd_yerrick AT hotmail DOT comSEND DOT SPAM> writes:
>
>> On Sat, 11 Mar 2000 10:22:23 -0600 (CST), GAMMELJL AT SLU DOT EDU wrote:
>>
>> > In high precision arithmetic, the assembly language commands
>> >mul, div, and adc are essential. In the 486 architecture, these
>> >commands are efficient. In the alpha architecture, they do not exist.
>>
>> WTF? Compaq's Alpha doesn't have multiply, divide, and add?
>
>According to the Alpha Architecture Handbook
>(ftp://ftp.digital.com/pub/Digital/info/semiconductor/literature/alphaahb.pdf),
>there is no integer divide instruction, and no add-with-carry
>instruction. The Alpha does have an integer multiply instruction, and
>also a floating-point divide.
Then it's flawed. How is an arbitrary precision math library
supposed to work on Alpha without add-with-carry?
>That's what RISC is about. :)
Is it about slow workarounds such as "convert numerator to floating
point, convert denominator to floating point, divide, separate into
integer and fractional parts, convert to integer, multiply fractional
part by divisor, convert to integer" just to get a / b? In some
cases, this slowdown defeats the purpose of running on an Alpha.
PowerPC (Performance Optimization With Enhanced RISC) has an
integer divide instruction, but this is swinging way offtopic.
--
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