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 A good CPU to start with? 
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Joined: Sun Apr 27, 2014 4:26 am
Posts: 3
Hi All,
New here but i have this question: what would be easiest to start with?

I have:
HD6303 x 1 [[ MC6800 compatable, tho technically it's an MCU that can be made to function as a 6800 ]]
M80C85A x 2 [[ These are 3Mhz 8085-As ]]
a eZ80
and a few Z80's (all Modern)
an i10188 x 1 [[ 8/16-bit MCU used in a few PC clones ]]

also have:
UV EPROM (MBM2764-30) x 4
SRAM (HM6116LP-3) x 2

serial and parallel (M82C55A-5 and M82C51A) from the board that houses the 8085's.

The 6303 board has UV PROM and a Dual Port SRAM (I would get the PN# but Id have to take apart a 7" CRT)

Trying to build out a SBC/Backplane system that I can cut my teeth on for programming micro's, so any input would be appreciated.


Sean

[[v0.1 - edited to clarify chip ID's]]


Last edited by Koriban on Tue May 06, 2014 2:02 am, edited 1 time in total.



Mon May 05, 2014 11:24 pm
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Location: California
I'm not familiar with all of those, but I think you'll find the 60's have a simpler bus structure than the 80's. I have an extensive primer on building 6502 computers at http://wilsonminesco.com/6502primer/index.html, and much of it will transfer.

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Mon May 05, 2014 11:43 pm
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Joined: Wed Jan 09, 2013 6:54 pm
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Please keep us updated on your progress! Like Garth, I come from a 6502 background, so would start with the 6303. Garth's primer is well worth some study.

(The 6303 is described as 6800 bus compatible, but has serial port and a little on-chip memory, and of course Hitachi's extensions to the instruction set: http://www.cryptomuseum.com/crypto/phil ... 6303rp.pdf)

Cheers
Ed


Wed May 07, 2014 9:07 am
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Joined: Sun Apr 27, 2014 4:26 am
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Will Do. :]
Been reading Garth's pages, also reading the 6800 UM's and applying what I can grok and glean to the design of the board I plan on taking the 6303 off, its the brains of an old fish finder display, so it does both graphics and communications to the rest of the system.
(I originally hoped i could get the 7" CRT working but its basically dead due to lack of knowledge)

Sean


Sun May 11, 2014 4:22 am
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Joined: Wed Jan 16, 2013 2:33 am
Posts: 165
I decided to break tradition and find a newer line of chips.
I decided to use ARM chips because they are a natural successor to the 6502 and I kind of remember they started off on the 6502 but wanted to speed it up and I think the difference is that the 6502 uses a VIA adapter chip on the outside whereas the ARM chip has components on the inside which I guess reduces cost because you don't have to interface two chips.

I basically looked at my budget, what I wanted to do and there are some low cost ARM chips that will let me start small and then I will have room to grow.


Wed May 21, 2014 12:01 am
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I think you mention two independent points here Chuck.

First, most homebuilds have historically made use of a CPU chip, usually in a DIP format, which exposes address and data bus and some control signals. They then hook up memory and peripherals. To do that, you need to understand a little about microprocessor busses, and then you need to write some software to control your new system. These days, and indeed for some time, you can buy system-on-chip devices which include the CPU and some peripherals and maybe some ROM and a little RAM. These SoCs sometimes do, and sometimes don't, offer a microprocessor bus to allow experimentation and further expansion. In this case, the 6303 is an SoC and it does expose a bus. The CPU is something like a 6800. In the case of an SoC homebuild, you still need to write the software to make a useful system, but you can get away with minimal hardware work. For some people's goals, that's a good place to be. For others, the bus and the external peripherals are part of the fun.

Second, there's the question of what CPU you'd like to use. As you say, ARM is a popular choice these days in consumer and industrial products, and the chips can be quite cheap. Even the dev boards can be quite cheap, so although most (but not all) of the chips are surface mount, you can avoid surface mount soldering if you wish to. However, I think pretty much all ARM chips are SoCs, and most of them don't offer a microprocessor bus. Some of them do offer a memory expansion bus.

Here's an ARM SoC in DIP: http://www.adafruit.com/blog/2012/03/13 ... -packages/

There are several links to ARM dev boards at http://forum.6502.org/viewtopic.php?t=1603

The Raspberry Pi isn't a dev board in the usual sense, but it is based on an ARM SoC, and you can program it at the bare metal: see for example https://github.com/dwelch67/raspberrypi

Cheers
Ed


Wed May 21, 2014 9:14 am
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Joined: Wed Jan 16, 2013 2:33 am
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According to my help:

Quote:
The FSMC peripheral allows direct mapping of external memories into the address space such as sram and flash. On the higher end F4's that includes SDRAM as well.


Do you believe that would be enough for most people?


Mon Jun 16, 2014 3:22 pm
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Yes, direct attach of a commodity memory chip to your ARM should be enough for most people. It does use a lot of pins though - would be worth checking in each case that you can still do whatever you wanted to do, with the RAM attached.

Edit: Oh, and I'm not sure what kind of access speeds you get - on-chip RAM is probably single-cycle (zero wait state) but external RAM presumably slower.


Mon Jun 16, 2014 3:45 pm
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You can buy 1.6 GHZ Dual Core Arm chips so it can compete with a computer these days.


Mon Jun 16, 2014 3:57 pm
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That's true, but the SoC ARMs I've been looking at go up to 168MHz (or maybe 180MHz now) - and even then, the flash memory can't quite keep up.

If you've spotted a faster ARM which you believe would be a practical basis for a homebuilt machine, it would be interesting to know more!

Cheers
Ed


Tue Jun 17, 2014 8:39 am
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BigEd wrote:
That's true, but the SoC ARMs I've been looking at go up to 168MHz (or maybe 180MHz now) - and even then, the flash memory can't quite keep up.

If you've spotted a faster ARM which you believe would be a practical basis for a homebuilt machine, it would be interesting to know more!

Cheers
Ed


Megol gave me these links for cheap ARM machines. The evaluation kits are not cheap, however. Thought they might interest you as you could do a lot with them. I got two books on ARM system architecture / programming. This is what Megol said:

"One can buy dual core 1.6GHz ARM computers for ~$50. A chip with a ~500MHz processor including graphics is ~$15 but requires making a motherboard and adding RAM."

http://www.digikey.com/product-highligh ... ex-a5/3294

http://dx.com/p/ug802-android-4-0-corte ... lug-154597

You can also buy high end ARM desktops because I've seen them. You just need to use their own operating system or make your own.

http://cubieboard.org/

http://www.glomationinc.com/products.html

http://www.natami.net/knowledge.php?b=2 ... order=&x=0


Tue Jun 17, 2014 1:31 pm
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Well, there are ARM systems and there are ARM systems. I don't think high-end desktops are quite the kind of homebuilt machine most of us here are thinking about. Any external signals over say 20MHz are going to be difficult to deal with, unless perhaps they are short and point-to-point.

Closer to home, here's an ARM SoC which is under 2mm square, with more than a dozen I/O pins:
http://www.digikey.com/product-detail/e ... ND/4309046
Surface mount, of course.

Cheers
Ed


Tue Jun 17, 2014 8:29 pm
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BigEd wrote:
here's an ARM SoC which is under 2mm square, with more than a dozen I/O pins

...for about $2. So much smaller, faster and cheaper than the stuff I used to play with! Sometimes I feel old. :cry:

-- J

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Wed Jun 18, 2014 3:47 am
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BigEd wrote:
Well, there are ARM systems and there are ARM systems. I don't think high-end desktops are quite the kind of homebuilt machine most of us here are thinking about.

I feel I should moderate this statement a bit. Some here do have in mind some serious computing power. Others are happy to put together a six-chip 8-bit wonder. So discussions all up and down the spectrum are welcome here: whether about PCBs or writing a monitor, whether writing microcode for a TTL machine or flashing code to an SoC.

But I do think it makes sense to set out, in any given project or conversation, what kind of thing we're talking about. This thread started with a query in the space of through-hole 8/16 bit single-board computing. In that space, hooking up a single SRAM or SDRAM to an ARM SoC does seem fitting. Whereas a conversation about a system running at some hundreds of MHz with some hundreds of megabytes of RAM probably deserves a new thread - it has quite different challenges.

Cheers
Ed


Thu Jun 19, 2014 8:39 am
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Wee an update >;)

I went with the 6303 with a single 16K chip out of the pair of them to start out with.
Have been working on the board layouts, and a simple bus design for the system.
I figure if I do a generic enough bus system and leave a lot of pins free to “improve” my design; I can squeeze what I want in the system later and not have to do much for re-implementing the IO and RAM boards if I get it right.
I'm hoping I can get my hands on another 6303 and some support chips for the 6800 and see if I can’t get a nice multiuser/CPU system cooked up.
I'm currently waiting for the chips to be returned to me from a buddy that agreed to remove them and do some testing to verify function.

I have had a nice run in with a dumpster recently, as I managed to score a nice Commodore 128 setup.
Now to get that guy doing something use full :)

Sean


Tue Jul 29, 2014 5:58 am
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