To state my point more clearly........
I did not say it was a 16-bit, I said it should have been a 16-bitter given the
fact that all the major players at the time wore working on or, already had
a 16-bit design in the cooker. Even Motorola was working on the 68000
already.
The 6809 would have replaced the 6502 and the 6800 in a lot of computers
if it would have been aviable sooner!
Sipke de Wal
----------------------------------------------------------------------
http://xgistor.ath.cx
----------------------------------------------------------------------
----- Original Message -----
From: Richard Erlacher <edick_at_idcomm.com>
To: <classiccmp_at_classiccmp.org>
Sent: Friday, May 04, 2001 8:15 PM
Subject: Re: How many transistors in the 6502 processor?
> I believe calling the 6809 a 16-bit machine is exaggerating somewhat. It had
an
> 8-bit ALU and an 8-bit data bus, and an 8-bit almost everything else. Even
the
> 6801 had instructions that would concatenate the A and B registers so a single
> instruction would operate on the pair, and the fact that the 680x series had a
> 16-bit index register was more of a hindrance than a help as far as
performance
> was concerned. The instruction set was very nice, though. Although the
> "internal architecture" supported 16-bit operations somewhat, it's a bit of a
> reach to compare it with, say, the i8088, which, though I hate the segmented
> effective address computation scheme, is, in fact, a 16-bit architecture, as
it
> has a 16-bit register SET, a 16-bit ALU, and 16-bit instructions that operate
on
> 16-bit operands.
>
> The 6502 had advantages over the MOT-style processors primarily BECAUSE of its
> 8-bit index registers. Because the index registers were a single byte, the
> state machine that controls the physical address computation doesn't have to
> decide to skip a cycle when the MS byte of the index is zero, nor does it have
> to decide what else to do with the upper byte, since there isn't one. Its
8-bit
> character is what makes it faster than the MOT equivalents. It does 8-bit
> things VERY fast, so long as they are scoped into table sizes easily handlled
> with the 8-bit index registers. Any 4 or 8 bit processor can process 16-bit
> data, given enough time and resources. Some do it more elegantly than others,
> and I freely admit that the 6809 does it more elegantly. It just doesn't do
the
> 8-bit stuff as fast as the 650x family.
>
> The fact is, the 650x family was a smaller chip than the MOT, Intel, or Zilog
> parts of the same class. That suggests it had fewer transistors, since the
> number of transistors would increase the chip size. Keep in mind, when
> considering this contrast, that the 650x's general purpose registers could be
> viewed to reside in the "zero-page" since the access to that region was faster
> than to the rest of memory. Having larger registers and more of them, as did
> the 8080 and Z80 certainly would make the chip larger and the transistor count
> larger.
>
> It has a pipelined data bus, which, in reality, is just double-buffer for the
> benefit of the instruction decoder, so it can decode the opcode WHILE the
> opcode's first operand, or the next opcode, is being fetched. While this
> doesn't speed up an opcode's execution in a test setting, it does speed up a
> sequential execution as you encounter when running code. If you look at what
> appears on the 6502's pins as it executes various instructions, you'll see
that.
> (this is documented in MOS Technology's 6500-Series Hardware Manual, so you
> don't have to dig out the logic analyzer.)
>
> Dick
>
> ----- Original Message -----
> From: "Eric Chomko" <chomko_at_greenbelt.com>
> To: <classiccmp_at_classiccmp.org>
> Sent: Friday, May 04, 2001 10:59 AM
> Subject: Re: How many transistors in the 6502 processor?
>
>
> > Sipke de Wal wrote:
> >
> > > With hindsight one can consider the 6502 to be the only 8-bit RISC CPU
> > > It had a reduced number of registers compared with the 6800 and this and
> > > other logic-reduction simplified the design so it could execute code a lot
> > > more efficiently as compared with the 6800. Also the 256-bytes Zero-page
> > > could be regarded as an (extended) RISC-like registerset of the CPU.
> > >
> >
> > Many looked at the zero-page and the 8 bit stack pointer as shortcomings.
> > It was the X and Y index registers both 8 bit, that made the chip
interesting.
> > The X/Y pair made memory-madpped video graphics easier to implement.
> >
> >
> > >
> > > I remember a magazine (BYTE?) describe the 6502 as a true RISC-chip
> > > but I don't thing the designers had RISC-CISC philosofies in their heads
> > > while working it out.
> > >
> >
> > RISC per se didn't come out until the 80s.
> >
> > >
> > > Only 6809 bas a "better" chip but that should have been a true 16-bit
design
> > > It came way to late to make a large impact. Only the COCO used it in a
> > > homecomputer.
> > >
> >
> > The 6809 was fine as a 8 bit chip with a 16 bit internal architecture, and
> many
> >
> > home computers used the 6809 CPU not just the CoCo.
> >
> > SWPTC made one. The operating system OS/9 was built around that chip.
> > Viirtually every manufacturer of the SS-50 bus had a 6809-based system, and
> > that
> > would be around a half dozen.
> >
> > The CoCo may be the most well known but not the only.
> >
> > Eric
> >
> >
> > >
> > > Sipke de Wal
> > > ----------------------------------------------------------------------
> > > http://xgistor.ath.cx
> > > -----------------------------------------------------------------------
> > >
> > > ----- Original Message -----
> > > From: ajp166 <ajp166_at_bellatlantic.net>
> > > To: <classiccmp_at_classiccmp.org>
> > > Sent: Friday, May 04, 2001 1:03 PM
> > > Subject: Re: How many transistors in the 6502 processor?
> > >
> > > > From: Brian Chase <bdc_at_world.std.com>
> > > >
> > > > >Does anyone know how many transistors made up the 6502? These days
with
> > > > >Intel's boasting of the number of transistors their latest processors
> > > > use,
> > > > >it'd be interesting to know what we used to get by using. What, it
> > > > can't
> > > > >have been more than a few thousand, right?
> > > >
> > > >
> > > > Memory says it was one of the lower transistor count cpus, very
efficient
> > > > design.
> > > >
> > > > >And then it'd be rather fun to implement your very own 6502 using 74*
> > > > >series logic chips.
> > > >
> > > >
> > > > I'd bet it would be fairly high chip count. IT would be interesting to
> > > > see how fast
> > > > you cound make it go.
> > > >
> > > > Allison
> > > >
> > > >
> >
> >
>
Received on Fri May 04 2001 - 17:53:20 BST