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What limited the use of the 6809 CPU in personal computers?

Why did manufacturers of home computers avoid using the 6809 CPU? I can't really see that anyone 'avoided' it. There have been many successful machines using the 6809. Beside the mentioned Tandy's ...
Raffzahn's user avatar
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34 votes

Motorola 6809 two stacks design

From Byte Magazine article on 6809, by Terry Ritter: Point 11: Tell me again about the stack pointers: why two stack pointers? Answer 11: Good Point. The original reason for adding ...
leek's user avatar
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32 votes

What limited the use of the 6809 CPU in personal computers?

While I don't know the answer to this, I'll hazard a few guesses: It was quite an expensive CPU. For example, in 1983 retail price in the UK was £6.50 for the 6809 or £12 for the 68B09, versus £3....
Jules's user avatar
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24 votes

Advantages of a Hitachi HD6309 versus a plain Motorola MC6809

The basic improvements over the 6809: - 2 more 8bit accumulators; additional 8 & 16 bit registers - native and 6809 emulation modes - fewer execution cycles in native mode - improved instruction ...
Brian Blake's user avatar
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23 votes
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Motorola 6809 Stack Blasting

The 6809 has a couple of instructions which provide very quick ways of pulling (popping) and pushing registers off and onto the stack, PULS/PULU and PSHS/PSHU. PSHx only takes 5 cycles plus one per ...
Stephen Kitt's user avatar
20 votes
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How did the 6809 achieve source-code compatibility with the 6800?

So far as I can see, the 6809 lacks instructions that the 6800 has, such as aba, eorb ABA becomes PSHS B; ADDA ,S+ - a nifty use of the autoincrement feature. It shows as well were the temporary byte ...
Raffzahn's user avatar
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18 votes
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Are the 6809 and 6809E different from a programmer's point of view?

To directly answer the question: there is no difference whatsoever on the software side. The CPU core and indeed the die inside the package is exactly the same, just different pins are bonded out in ...
Chromatix's user avatar
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17 votes
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Why was the 6809 so expensive?

The price was defined obviously by marketing team, therefore their decisions are out of reach for the logical engineering mind :) Probably they were relying on the marketing company (like this one ...
lvd's user avatar
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16 votes

Why was the 6809 so expensive?

It was just standard market positioning. The 6800 was still a current product and in use in many systems at the time, so they priced the 6809 as a more powerful alternative to both that and the Z80. ...
user's user avatar
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16 votes
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How to use rounding with 6809 multiplication

The rounding capability is useful when doing fixed point math with exactly eight fractional digits. For example, supposing that the number in A is a fixed-point number with 2 fractional digits, and ...
Wayne Conrad's user avatar
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14 votes

Are the 6809 and 6809E different from a programmer's point of view?

There's your answer, right there: the 'E needs an external clock as well That's it. From the software side, there's no difference. (Also: The pinouts differ in 4 out of 40 pins. I wouldn't call that ...
Michael Graf's user avatar
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13 votes
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Motorola 6809 two stacks design

Well, the intent behind the two-stack design we can only guess today. It was definitely not the same as the intent behind the later development of User and Supervisor Stack in the Motorola 68000. The ...
tofro's user avatar
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13 votes
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Calculating the time for a CPU cycle

It's one divided by the clock. So for 0.895 MHz divide 1 by 895000 and the answer is 1.117318 micro seconds. for 1.79 Mhz it's 558.6592 nano seconds. I suspect however that the clock will be some ...
PeterI's user avatar
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13 votes

Why did MC6809(E) require two-phase clock consisting of two square waves shifted by 90°?

E is used for memory selection in a similar way as 6502 do (or 6800 phi2). Q should be used as a signal "data stable" (due to "The MC6809 Cookbook"). Let me quote: Addresses from the MPU will be ...
Martin Maly's user avatar
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13 votes

How useful were the 6809/6309's indirect addressing modes?

The 6809 offers to combine indirect with either a fixed extended (16 Bit) address or all indirect indexed modes. These modes are extremely useful for all kinds of linked list and/or table processing. ...
Raffzahn's user avatar
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11 votes

Fate of mystery Motorola RMS graphics chipset (68486 + 68487)

Based on the absolute dearth of information on the Motorola 68486/68487 video chipset (RMS), I would conclude that it was never officially released as a product for OEMs, and was therefore never used ...
Brian H's user avatar
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10 votes

How useful were the 6809/6309's indirect addressing modes?

Although not too obvious, almost every feature of 6809 looks like specially made for high level languages like C and for 'serious' systems like OSes. For example, indirect addressing is convenient to ...
lvd's user avatar
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9 votes

Advantages of a Hitachi HD6309 versus a plain Motorola MC6809

This PDF (link stale; here's an archive.org link) by Darren Atkinson gives you everything you want to know about programming differences between the two. It begins with a very thorough Leventhal-style ...
JCCyC's user avatar
  • 191
8 votes

Advantages of a Hitachi HD6309 versus a plain Motorola MC6809

Pin and software compatible. Two extra 8-bit accumulators. Instruction fetch pipeline. Division instruction. Lower power consumption.
tlindner's user avatar
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8 votes

Why did MC6809(E) require two-phase clock consisting of two square waves shifted by 90°?

The skew between min and max propagation delays was a lot larger in old multi-micron NMOS processes (an understatement). The digital rise and fall times could be quite asymmetric. This made ...
hotpaw2's user avatar
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8 votes
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Where can I find the Motorola Application Note AN-754?

The following book at archive.org contains several applications notes. Among those you have AN-754 on pp. 21-32.
UncleBod's user avatar
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8 votes

What does the DAA instruction do?

The DAA instruction on 6800 just works on the accumulator based on the data it contains and the flags register as set by the previous instructions. So it does not know what instruction it was and ...
Justme's user avatar
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7 votes
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Hardware multipliers on classic CPUs

Can anyone offer some back-of-envelope sort of estimates of what sort of gate count was needed to add a multiplier to 8-bit CPUs? An 8x8 array multiplier build from 6T adders comes down to 8x8x6=384 ...
Raffzahn's user avatar
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6 votes
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Can anyone identify this Parallel to Serial Interface Board?

The boards are essentially "serial to parallel converters," but probably not of any type anybody here is familiar with. A manual has been found that describes two devices, the MSD-1 Multiple ...
cjs's user avatar
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6 votes
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Fate of mystery Motorola RMS graphics chipset (68486 + 68487)

With some Google sorcery, I finally located a system that used the elusive RMS chip set: The Microbox 3 manufactured and sold by UK-based company "Micro Concepts" from Cheltenham! I can only find it ...
Fedor Alexander Steeman's user avatar
6 votes

Hardware multipliers on classic CPUs

The first production 6809 was fabricated around 3 years after the first production 6502, and thus, according to the Moore's Law rate of transistor density improvements, was likely fabricated using a ...
hotpaw2's user avatar
  • 8,125
6 votes

HD63B03R timer interrupt frequency

Your analysis seems pretty good. To confirm, the E clock is 1/4 the oscillator frequency. The data sheet also states that the free running counter (FRC) is driven by that same E clock. Your ...
Peter Camilleri's user avatar
6 votes

How to use rounding with 6809 multiplication

TL;DR: It allows the use of MUL as part of a Multiply-Accumulate operation, by providing the rounding factor from the multiplication for a follow up addition. MAC instructions are an essential part of ...
Raffzahn's user avatar
  • 213k
6 votes

How to use rounding with 6809 multiplication

Like it says, it is useful for rounding the most significant byte. If you are only interested getting a 8-bit answer, and thus want to discard the low 8 bits of the multiplication. If the answer would ...
Justme's user avatar
  • 28.3k
5 votes

What limited the use of the 6809 CPU in personal computers?

While the 6809 had (and still has) technical applications, it lost out badly in the consumer market in the “mug's eyeful” department: if you were buying your kid a computer for Christmas and didn't ...
scruss's user avatar
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