strangest systems I've sent email from
bfranchuk at jetnet.ab.ca
Tue May 24 22:47:40 CDT 2016
On 5/24/2016 3:32 PM, Swift Griggs wrote:
> On Tue, 24 May 2016, Fred Cisin wrote:
>> (OB_Picky: Due to the overlap of segment and offset, on machines that had 21
>> address bits, real mode actually had a maximum of 1114096 (10FFF0h) bytes,
>> instead of 1048576 (100000h).
> This was always the biggest pustule on the facade of x86 to me. Gate A20
> and other chicanery was nasty business. It always struck me as a hardware
> hack to work around earlier bad design. Sure, you can eschew segmentation
> and try to use multiple instructions to delivery some flat addressing, and
> then your code was snail-slow. Real mode in 16 bit on x86 was/is some
> fairly vulgar stuff due to segmentation (hate hate hate). Then it was made
> "all better now" by protected mode and segment descriptors later *pat
> pat*. Yeah. Ugh. Pleah. Ick.
I think Windows made it big because they could handle the flat 386 model
and dos did not.
> All that fun sent me running into the arms of the M68k and it's git, and
> later MIPS (queue hallelujah chrous from the clouds). I'm not a MIPS god
> (we have a some here), but much love and respect to the architecture
> nonetheless. I know enough to know "that's the good stuff". Nowadays I
> wonder, since I'm using flat memory on the Unix boxes I code in (now
> pretty much just in C, I haven't done ASM in a long while), what kind of
> masochist maintains the SLAB/SLUB allocators for x86 Unix variants these
> days. I want to buy them a six pack, pat them on the back, and say "you're
> a braver man than, I."
I never could buy the RISC argument of being a faster design.
Data access to main memory is allays what slows a system down.
Still playing around with TTL macros with Altera FPGA here,
planning mid 1970's TTL CPU. The cleanest version so far
is 2 -16 LS bit ALU boards and 1 control card. This gives
me a CPU with 2 sizes of data - BYTE and WORD and a WHOPPING
5 registers. PC, AC1 , AC2 , INDEX , STACK.
No risc here, just a simple CPU.
PS: NO blinking lights sadly.
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