23 Nov
2023
23 Nov
'23
7:18 p.m.
The 4040 was more of an enhanced 4004. It had a deeper stack ( 4004 was only 3 levels ),
It had interrupt capabilities and a second register bank.
The mulplexed bus was almost identical except the 4040 had one additional bus operation. I
forget the exact difference.
Still, people seem to think that the 4004 wasn't a capable microprocessor. Benchmarks
showed that much code was faster on the 4004 than the 8008, if working in BCD math.
The main reason the 4004 was thought of as just a calculator chip was that the chipset
that it originally came with, the ROM and RAM, was to use a minimal additional amount of
custom bus circuity for the Busicom project. I guess it wouldn't be a real uP if one
didn't have to create bus buffers and address decoders.
As an example, Tom Pittman wrote a two pass assembler that ran on the SIM4-01( 4ea1702.s
or 1k of code! ). That seems to be a uP type of process, to me. I should note that
Tom's code won't run on a 4040 without modification. This was because he took
advantage of the fact that the stack would overflow on the fourth subroutine push. The
4040 had a deeper stack. Still, the 4004 could handle text as well as do calculations.
Probably, the main thing that tended to put it in the calculator bucket was the restricted
instruction memory range, without using some form of bank swapping. Its natural memory
range was limited to 4096 addresses. But then, the 8080 was considered a real uP with
similar restrictions to 64K.
Both the 4004 and the 8008 used a multiplexed bus, for the 8008, one had to design their
own bus interface. The 8080 was what made the type of uP we tend to think of. It had
separate data and address busses ( note the 8085 and 8086 both multiplexed the address and
data buses. A step back I'd say. )
I'd say things really started to happen when they created the 6502. That brought the
pricing into a range that people could start small and expand to bigger things.
Dwight
________________________________
From: ED SHARPE <couryhouse(a)aol.com>
Sent: Wednesday, November 22, 2023 7:43 PM
To: General Discussion: On-Topic and Off-Topic Posts <cctalk(a)classiccmp.org>
Cc: dwight <dkelvey(a)hotmail.com>
Subject: Re: [cctalk] Re: Intel 4004(sp?)
Ibad an intellectual 4 offered to me one time that had a 4040 in it. Is t a 4040 like a 5
but more of the aux chips integrated? Is instruction set the same?
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Android<https://play.google.com/store/apps/details?id=com.aol.mobile.aol…
On Wed, Nov 22, 2023 at 8:34 PM, dwight via cctalk
<cctalk(a)classiccmp.org> wrote:
The Intlec 4 was no more or less a computer than the Altiar or IMSAI was. It didn't
typically have as much RAM but one could write and run code on it.
As for the F14 processor. For the purpose used, it was likely a DSP. More intended to do
matrix multiplication using adds and shifts. This would be similar to Intel's early
try at a DSP.
The F14 processor was said to control the flight surfaces. Like the Intel 2920 ( not to be
confused with the AMD bit slice part) it likely ran tight loops of signal processing
operations using tables of lookup coefficients.
Dwight