How many transistors in the 6502 processor?

From: ajp166 <ajp166_at_bellatlantic.net>
Date: Fri May 4 06:13:46 2001

From: jpero_at_sympatico.ca <jpero_at_sympatico.ca>
> From: Brian Chase <bdc_at_world.std.com>
>
> And then it'd be rather fun to implement your very own 6502 using 74*
> series logic chips.

>Possible, but length of traces to wire all those together will keep
>it to KHz range and needs few large boards that needs so much power
>that hottest athlon cpu is low power by comparsion.


It would eat power but it would not be that slow. The mos logic of
the time was quite slow compared to the ttl of the time.

I did do a 2901C version of z80 and it was much faster than the MOS
version, not due to the 2901s as they were logic savers but the
acutal speed bottleneck as well.

I have seen photos of apple IIe prototype laid out on early
pre-production logic board, one of that 40 pin chipset socket is
hooked to a equally same size board filled to the 4 edges with
tightly packed TTLs and few large ICs, I think it was shown in Byte
as well as few other publicatons. Large board full of chips vs. 40
pin IC, same thing...Amazing!


That was replaced by a 2000 or so gate array so thats were it
all went. Also the proto was built of all SSI TTL making it less dense.

I did some work like that in the early 80s. Logic was faster than
you think. It's true to get to the sub 100ns range for serious
cpus you have to get the interconnect problem out of the way.
However for a fairly fast machine (4-10mhz clocks) there are
many examples that are mostly ttl. For starters the PDP-8E
ca. 1971ish executes instructions in 1.4uS for the base modes
and that was SSI ttl on low density boards. FYI it was limited
by the core cycle time not the TTL, I ran one at nearly twice
speed easily with semicon memory.

Allison
Received on Fri May 04 2001 - 06:13:46 BST