OT? What 8bit Microprocessors still available new?

From: Dwight K. Elvey <dwight.elvey_at_amd.com>
Date: Thu Feb 19 20:09:48 2004

 Why not go with something like one of the DSP chips.
The ADSP218x family of parts are enough like a real processor
that one could do quite a bit. They don't require much
external glue parts and can bootstrap them selves from a flash
memory. The 2181 has 80K or so of internal RAM and
runs at around 30 mips ( or more for newer versions ).
You don't even have to deal with the DSP functions if
you don't want to. They are still a very powerful processor.
 Things like bit-banging old flopy disk or tape drives
are well within it's capabilities ( I mean raw data ).
One can buy demo boards for around $100 and then make
add-ons to increase it's functions.
 Anyway, just a thought.

>From: "J.C. Wren" <jcwren_at_jcwren.com>
> If I were going for audience appeal, and you don't plan to be
>booting CP/M or some other free readily available O/S from the get-go,
>I'd aim for something that was was well supported. For me, SIMH was a
>powerful tool in getting the Z80 SBC up. I'd compile the BIOS under the
>SIMH Z80 emulator running CP/M, upload it to the Linux box, and download
>it to the ROM emulator. Turn around time was very quick.
> Problem is, Z80's aren't real interesting. There's lots of
>software, but they're kinda old hat. Homebrew 6502 systems seem a lot
>less common, making thier interest level, for me, higher. 1802's even
>more so. I would favor a CPU that has a static core. Being able to toy
>with the clock is helpful, especially in the early stages of bringup.
> While concievable that you could write a disk-based OS on a 8031,
>the architecture doesn't lend itself well to that. I'd pick something
>that has a real stack, with a real von-Nuemann architecture. Yes, you
>can play games with an 8031 and overlap the code and data space by
>AND'ing /PSEN and /RD, but the instruction set still lacks a real stack,
>and you're limited to 1.5 16 bit registers (I'm counting the MOVX _at_P2 mode).
> Obviously, building something with an external 32 bit bus is going
>to be more work than a 8 bit or 16 bit bus. 16-bit address and 8 or 16
>bit data would be middle of the road. Are you going to stick to 5V
>logic, or 3.3V? With 3.3V logic, you've got a lot more available
>choices, these days. If you wanted to play with an ARM core, as far as
>I know, there are no 5V ARM cores. Or if there are, they're not very
> One neat part is the Philips LPC2106. 128K bytes FLASH, 64K bytes
>RAM, all on chip. ARM core, timers, 2 serial ports, GNU tools readily
>available. But it's SMT only. And 3.3V I/O with a 1.8V CPU core.
> Something like a 6809 would be fun (I like those). When you're
>done, you could boot OS/9 or Flex/09. If you want to write on the bare
>metal, it's got a nicer instruction set than the Z80, but lacks
>registers. You make up for that with more addressing modes, and better
>relative branches. With a 6809E, the bus interface doesn't get much
>easier. The original 6809 was a lot more trouble to work with because
>of the clock requirements.
> 1802s are fun, too. The have a really neat instruction set that's
>way ahead of it's time, in some respects. It lacks a real stack,
>however, so you have to use 7 instructions are so to build a real stack
>in external memory. There's a fair amount of software, but CPUs are
>going for ~$10/ea, and the commonly availabel CDP1802ACE is only a
>3.2Mhz part. If you want the 5Mhz part, you need a CDP1802BCE, and
>those are going for a lot more money. The max specs say you can run a
>1802 at 6.4Mhz with 10V, but the > 5V parts are less common. You also
>have to use all CMOS glue logic. Single stepping and using switches to
>enter/edit memory is trivial. The CPU design supports that pretty much
>instrinsically, with little extra logic needed.
> Then there's the venerable 6800. Lots of software, lots of
>emulators, and OSs are available. Common, easy to find. Sorta like the
>Z80, though. It's common.
> You could build a 68000 system. Those are pretty easy to find, have
>good support, etc. 68K homebrew systems seems to be far less common
>than Z80s and 6800s. I don't know what support chips you'd need/want to
>make it play. I've used 68K systems, but never built my own. Slightly
>on the sluggish side, if you're looking for speed. I don't think the
>68Ks started getting fast until the 68030 or so. The 68020 was better,
>but still no speed demon, IIRC.
> The NSC32000 would be an uncommon homebrew system. Software may be
>hard to find, including emulators. I don't see a lot of 32K parts going
>by on eBay, so you might be hard pressed to come up with what you need
>one. Same for the Zilog Z8000.
> These are all the common 8, 16 and 32 bit systems I can recall. At
>some point, trying to homebrew something like an 80286 gets to be too
>much trouble. And little reward, in my book. I feel good everytime I
>throw away anything x86 that's less than an Athlon 1Ghz. And even those
>are getting ready to get moved to the "why bother?" list. There were
>some oddities, like the 6502 Forth chip, and several other Forth
>processors. I don't think I'd want anything with BASIC build in, like
>the 8031AH-BASIC (you said you wanted bare metal, anyway).
> Any basic families I missed here, not counting variants like 6510s,
>CDP1805s, etc?
> --jc
>Ron Hudson wrote:
>> On Thursday, February 19, 2004, at 04:06 PM, Philip Pemberton wrote:
>>> I'd be very tempted to add GPIB (aka HPIB, aka IEEE488) just because
>>> it's a
>>> very usable bus for connecting stuff like disc drives up.
>>>> Best use would be to connect it to a PC running a terminal emulator for
>>>> IO and Mass storage.
>>> I'd also add an IDE interface and an 80MB hard drive - fun factor
>>> again :)
>> I suppose we'll have to take the busses out to an edge-card connector...
Received on Thu Feb 19 2004 - 20:09:48 GMT

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