Author Topic: 6502 Cpu wanted  (Read 8511 times)

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Offline eugenenine

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Re: 6502 Cpu wanted
« Reply #25 on: February 15, 2017, 12:27:50 pm »
The whole retro computing in an in thing now so everyone is buying them and the prices are high.   I've only had any decent luck just finding old stuff local (craigslist, etc) but even the the prices are much higher than they used to be.

You may just have to eat the shipping cost from Jameco or one of WDC's distributors.

I tried to do a proxy once a few years ago and add a few parts to one of my orders then forward to someone in another country but there are so many laws and regulations just to walk into the post office before you even try to ship anything, shipping anything is a complete mess now a days.
 

Offline james_s

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Re: 6502 Cpu wanted
« Reply #26 on: February 15, 2017, 09:21:40 pm »
That happens with everything though, everybody throws most of it away, so the stuff that's left is harder to find and commands higher prices. It's too bad there isn't a computer graveyard in a warehouse out in the desert somewhere cheap like the graveyard for old aircraft. A lot of cool old stuff could have been saved for future generations to play with.
 

Offline eugenenine

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Re: 6502 Cpu wanted
« Reply #27 on: February 15, 2017, 09:35:42 pm »
I hate that about the whole e-waste thing too.  people bring their old computers and they get sent to china and scrapped.  Some people don't know the value of a commodore or amiga and they end up there or in trash.
 

Offline Chopsticks

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Re: 6502 Cpu wanted
« Reply #28 on: February 16, 2017, 04:08:29 am »
im not to sure what goes on here in Australia, we do have some recycling centres in some cities for e-waste but as it costs money most people seem to just throw electronics out in the trash (bad practice i know).

i always tell my friends and family to send all there stuff my way first so i can salvage anything of use such as motors, IC's (not common chips but unique or hard to get ones) and so forth but I've yet to come across any vintage electronics from my small network of family and friends...
 

Offline james_s

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Re: 6502 Cpu wanted
« Reply #29 on: February 16, 2017, 05:22:53 am »
Do you have Craigslist or something like it there? Thrift stores? Maybe you can find a group or club of vintage computer enthusiasts? That's a great way to network with people who may have extra stuff available. Most 6502 systems are now old enough that they are either long gone and buried or they are in someone's collection.
 

Offline Chopsticks

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Re: 6502 Cpu wanted
« Reply #30 on: February 16, 2017, 06:00:14 am »
there is gumtree thats similar to crags list but i never see anything good on there vintage electronics wise. While it would be amazing to get an old 8 bit system and start learning what can be done with it, unless someone has one to donate i think that ill end up just wording some new chips or mouser when i have a bit of spare cash for another shopping spree

on a side note, i just wanted to thank everyone for all the help and suggestions, I've been a member for awhile now but rarely post anything however its been great knowing that this forum is so helpful to myself any others when we get stuck
« Last Edit: February 16, 2017, 06:02:14 am by Chopsticks »
 

Offline james_s

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Re: 6502 Cpu wanted
« Reply #31 on: February 16, 2017, 08:53:29 am »
Well there's certainly fun to be had in building your own. You might be interested in this:

http://searle.hostei.com/grant/6502/Simple6502.html
 

Offline Chopsticks

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Re: 6502 Cpu wanted
« Reply #32 on: February 17, 2017, 02:20:20 am »
I bookmarked that link a couple days ago, between that and Quinn's Veronica computer project there's a good deal of useful information I'll be able to cobble together :)
 There's also a couple other 8 bit minimal chip designs on that site for the z80 if memory serves correct
 

Offline TNOBLE8888

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Re: 6502 Cpu wanted
« Reply #33 on: July 27, 2017, 01:59:05 am »
Hey there, I have a virgin 6502 and a couple 6522 (I/O ports), if still looking.
 Thom
A lifetime of electronics prototyping, hacking hardware and integrating with a system-of-systems engineering perspective.
 

Offline tiger99

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Re: 6502 Cpu wanted
« Reply #34 on: August 07, 2017, 11:31:15 pm »
It was noticeable at the time that 6502 based computers seemed to be consistently slightly faster than those based on the Z80. I suspect that the small instruction set forced better programming techniques, or maybe just made it easier.

But what I did find surprising is that a BBC Micro, running an 8 bit 6502 at 2MHz and with no floating point hardware, consistently beat an original 16 bit IBM PC/AT, with an 80286/287 running at 6MHz and hardware floating point, by a factor of between 2 and 5. The programs were partial helicopter simulations, as we were designing autopilots at the time, and some minimal translation between Basic dialects was done to enable what had been written in M$/IBM ROM Basic (apparently translated from the original code for the 8086 by Gates himself) to run on the BBC. The engineers who witnessed these trials were suitably impressed, and thereafter paid little credence to Gates and his alleged programming skill. We also tried some kind of Basic on a PDP11-45, which thrashed them both of course, but not by very much.

The BBC could do in 32k (yes, k, not M or G!) of RAM what seems to take bloatware programmers a minimum of 1000 times more to do these days, thinking about the bloat of most mobile apps, for instance. It sickens me to see the way software development has gone, all the power ans speed of modern hardware being gobbled up by bloatware. The great virtue of a 6502 is that it forces you to think properly, and not waste precious instruction or data space or machine cycles. But note that the BBC had a very well coded Basic interpreter in a 16k ROM and an unusually comprehensive and also well coded operating system in another 16k ROM, which were of immense help in getting it to do what was wanted efficiently.

I would suggest that everyone who writes code should have a go at an old 6502 based system from time to time. It encourages good habits.
 

Online brucehoult

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Re: 6502 Cpu wanted
« Reply #35 on: August 08, 2017, 01:12:39 am »
I would suggest that everyone who writes code should have a go at an old 6502 based system from time to time. It encourages good habits.

I really can't agree with this part.

I cut my programming teeth on the 6502, and it's main virtue was costing eight to ten times less than its competition.

If you want 8 bit nostalgia, the 6809 had almost all the same virtues, while being a whole lot more pleasant and efficient in execution and programmer effort.
 

Online Kleinstein

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Re: 6502 Cpu wanted
« Reply #36 on: August 08, 2017, 10:21:11 am »
The 6502 was about as fast as an Z80 system running at 3.5 to 4 times the speed. However clock speeds where also at about that ratio: 6502 often a 1 MHz and Z80 at 3.5xx MHz.  The early PCs where relatively slow. This is only partially due to the software, but also from some slow software and using the 80286 most of the time in 8086 mode only. Especially DOS code often did not use an FPU unless specially complied for it. So the basic comparison might have just ignored the FPU. A 2 MHz 6502 might thus compete with a 6 MHz 8086 - especially if the code is written for low width data.
 

Offline bsudbrink

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Re: 6502 Cpu wanted
« Reply #37 on: August 08, 2017, 03:39:16 pm »
Here's a higher res version of my avatar, how "real men" (just kidding) learned to program the 6502 back in the day:

 

Online PA0PBZ

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Re: 6502 Cpu wanted
« Reply #38 on: August 08, 2017, 05:18:17 pm »
Here's a higher res version of my avatar, how "real men" (just kidding) learned to program the 6502 back in the day:

Don't you love it when the data bits outnumber the address bits? :)

But it's true, once you learned how to program things like this (a KIM-1 for me) you never forget how assembly language works.
Keyboard error: Press F1 to continue.
 
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Offline bingo600

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Re: 6502 Cpu wanted
« Reply #39 on: August 19, 2017, 09:07:38 am »
I'd go for the FPGA ($13) version  (I have the FPGA board as a MC6809)

http://searle.hostei.com/grant/Multicomp/

And this baseboard
https://www.retrobrewcomputers.org/forum/index.php?t=msg&th=19&start=40&

Using NealC's implementation (MC6809 or Z80)
https://www.retrobrewcomputers.org/doku.php?id=boards:sbc:multicomp:cycloneii-c:start#downloads


/Bingo
 

Offline james_s

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Re: 6502 Cpu wanted
« Reply #40 on: December 05, 2017, 08:46:43 pm »
I made a similar daughterboard some time back that does roughly the same thing but it's much smaller than that baseboard. I'll post the design here when I get home in case anyone wants to make one, I've got all three varieties running on the hardware, 6502, 6809 and a decked out Z80 system running CP/M.
 

Offline stj

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Re: 6502 Cpu wanted
« Reply #41 on: December 06, 2017, 12:44:29 pm »
what's the goal here?
if you just want to write code then use an emulator - like MAME.
emulate an apple2 or a bbc micro and write your code in the emulator.
mame has a debugger & dissassembler built in you can cheat with!  :-+

6502 was faster btw, because it had very low cycle-count operations.
there was a video on utube of an interview with a guy from Atari arcade-division - possibly Edd Logg,
he was saying that a 6502 cound run code almost as fast as a 68000, and the only reason they switched was to get the bigger memory-map!
 

Online brucehoult

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Re: 6502 Cpu wanted
« Reply #42 on: December 07, 2017, 07:40:07 pm »
what's the goal here?
if you just want to write code then use an emulator - like MAME.
emulate an apple2 or a bbc micro and write your code in the emulator.
mame has a debugger & dissassembler built in you can cheat with!  :-+

6502 was faster btw, because it had very low cycle-count operations.
there was a video on utube of an interview with a guy from Atari arcade-division - possibly Edd Logg,
he was saying that a 6502 cound run code almost as fast as a 68000, and the only reason they switched was to get the bigger memory-map!

Code with 8 bit variables only, i the 68000 is running at twice the clock speed of the 6502 .. ok, maybe.

1 or 2 MHz 6502 vs 8 MHz 68000 ... not a chance.
 

Offline stj

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Re: 6502 Cpu wanted
« Reply #43 on: December 08, 2017, 08:08:20 am »
2MHz 6502, vs 7MHz 68000
and his comment was based on real hardware his unit built running software his team wrote - so i trust him.
 

Online brucehoult

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Re: 6502 Cpu wanted
« Reply #44 on: December 08, 2017, 09:04:30 am »
2MHz 6502, vs 7MHz 68000
and his comment was based on real hardware his unit built running software his team wrote - so i trust him.

I don't believe it.

6502 takes 1 clock cycle per byte read/write (including instruction fetch), with a minimum of 2, plus 1 extra for a taken branch, or for a carry (page crossing) during indexed addressing or branch offset calculation.

68000 takes 4 clock cycles per byte or word read/write (including instruction fetch), plus 2 more for indexed addressing (each operand) or a taken branch.

So, on the face of it, it looks at first that a 2 Mhz 6502 and 8 MHz 68000 are going to have similar timings.

The problem is, the 6502 usually needs several instructions to do what the 68k can do in one.

For example, your commonly-used variables are usually in registers on 68k and in Zero Page on 6502. The 68k does a register-to-register add in 4 clock cycles (8 for a = b + c rather than a  += b because it needs an extra move). The 6502 needs 11 cycles for 8 bit variables (CLC, LDA, ADC, STA) or 20 cycles for 16 bit variables.

If they were clocked the same and you only needed 8 bit variables then the 6502 would be not too far off. But that's not the case. The 68k is clocked 3 or 4 times faster.

What about memory block moves (often a limiting factor)?

The 68k typically does "move (an)+,(an)+; dbne" for 22 cycles for copying either a byte or a word at a time. (let's ignore 32 bits at a time, which is 30% faster again). 6502 typically does "lda (zp),y;sta (zp),y;dey;bne" for 15 cycles per byte assuming no page crossing. If you don't mind self-modifying code you can cut the 6502 time down by 2 cycles. Unrolling has a similar effect for both, so I'll ignore that.

So, again, if they were clocked the same and the 68k is restricted to byte-at-a-time then the 6502 is competitive .. even a little faster. But, again. the 68k is actually clocked 3 or 4 times faster.

I'm sorry, but I just don't see it.
 

Online brucehoult

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Re: 6502 Cpu wanted
« Reply #45 on: December 08, 2017, 09:41:17 am »
Oh, one possibility. Maybe your friend was not talking about the 68000 but the 68008 which, like the 8088 in the original PC, used an 8 bit bus. That might hobble it almost enough for the 6502 to be somewhat speed competitive on some programs.
 

Offline stj

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Re: 6502 Cpu wanted
« Reply #46 on: December 08, 2017, 02:41:31 pm »
memory block move in atari's case can be done using the blitter chips - so it does not count.
 


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