signed nibble

[Patrick Schluter]

On Monday, 7 January 2019 at 21:46:21 UTC, H. S. Teoh wrote:
> On Mon, Jan 07, 2019 at 08:41:32PM +0000, Patrick Schluter via 
> Digitalmars-d-learn wrote:
>> On Monday, 7 January 2019 at 20:28:21 UTC, H. S. Teoh wrote:
>> > On Mon, Jan 07, 2019 at 08:06:17PM +0000, Patrick Schluter 
>> > via Digitalmars-d-learn wrote:
> [...]
>> > > Up to 32 bit processors, shifting was more expensive than 
>> > > branching.
>> > 
>> > Really?  Haha, never knew that, even though I date all the 
>> > way back to writing assembly on 8-bit processors. :-D
>> > 
>> Most of my career was programming for 80186. Shifting by one 
>> was 2 cycles in register and 15 in memory. Shifting by 4, 9 
>> cycles for regs/21 for mem. And 80186 was a fast shifter 
>> compared to 8088/86 or 68000 (8+2n cycles).
>
> I used to hack 6502 assembly code.

Yeah, that's also what I started with, on the Apple II in the 
early 80s. I was quite surprized that my 6502 knowledge came in 
very handy when we worked on dial-in modems in the late 90s as 
the Rockwell modems all used 6502 derived micro-controllers for 
them.

> During the PC revolution I wrote an entire application in 8088 
> assembly.  Used to know many of the opcodes and cycle counts by 
> heart like you do, but it's all but a faint memory now.

I had to lookup the exact cycle counts ;-) . I remember the 
relative costs, more or less, but not the details anymore.