Could I use a 65c22 to drive an EIA232 interface?

[kc5tja]

An interesting question -- I'm not too sure. Everything is on-chip, so that rules out the breadboard. But, yet, it's in DIP form-factor, allowing it to sit on a breadboard.

I would have to accept defeat on that one.

I suppose what I meant was to build a complete computer system, with a sizable amount of RAM (say, matching the 65816's 16MB or more), a sizable collection of I/O peripheral chips, etc. In other words, something which you can look at and say, "yes, this is a PC," versus something a bit more purpose-built.

So, maybe what I really want to make for the challenge is this: something which consists of at least three chips, and which has interconnects between these chips operating at a frequency in excess of 79MHz.

[meganb]

I think for learning purposes, to use a breadboard to build a simple 6502 computer is quite the right thing to do. If it works consistently, then what's the problem (which it does). We can go on and on about good practice, etc.etc... but were not trying to launch the space shuttle here... just have some fun with IC's.

I'm sure at some point you will come to a limit, but I have never encountered an issue with my 2Mhz system on a breadboard. I have run applications days on end with no errors of any type, unless you include programming errors

I agree that the 5ns Rise and Fall times are strict... but they are obviously not too hard to acheive given the 2 pin crystal with older 74LS gates used on my system.

That's my 2 cents anyway....

[kc5tja]

Hmm, in my circuit, I had to resort to using 74F logic -- LS was just too slow (7ns rise/fall times for me). I later switched to a 4-pin metal can oscillator, and freed up a bit of space.

[BitWise]

Lost wrote:

kc5tja wrote:

I challenge anyone to build an 80MHz, fully functional computer using only breadboards as its substrate. You cannot use FPGAs (since in order to couple the FPGA to the board, you'll need to use a PCB, something I must forbid for this challenge for maximum fairness). Good luck.

This might be a stupid question, but does the http://www.xgamestation.com/view_product.php?id=34 count?

The microcontroller clocks internally at 80MHz. Very few of the signals coming from it will be anywhere as fast.

Opps didn't see the posts on the next page. Ah well.

[meganb]

kc5tja wrote:

Hmm, in my circuit, I had to resort to using 74F logic -- LS was just too slow (7ns rise/fall times for me). I later switched to a 4-pin metal can oscillator, and freed up a bit of space.

Maybe it had more to do with your circuit design then the 74LS switching time? Or maybe the W65C02S 5ns F&R times are a bit conservative... Just speculation.....

[kc5tja]

Nope -- the circuit was drop-dead simple: CPU, RAM, and one VIA chip, all placed as close as feasible next to each other, along with the clock circuitry. 74LS logic is too slow for the 65816's clock on the breadboards I used.

[meganb]

ahhh... the 65816 must be more strict then the W65C02S... I'm curious now... think I'll order a 65816 and see if I can get it to work on the same board.

[defzonoc]

parallel is easy and if you get a real oldie like my apple 2e you can make a eeprom programmer EASY plus the guy talkin bout breadboardin a comp is silly your cpu is not TO fast as you dont have to run it at top speed now do you?
my prom writer on my 2e is breadboarded and it writes a 32k prom in 1.4sec your problem is best solved through creativity any device you can rig up will be great who knows you may invent the newest line of storage rates on your 6502 SBC it can happen

[defzonoc]

the 65816 is odd as it multiplex the databus and adressbus now if you think you need 16mb addresses great otherwise its a big timewaster WDC's w65c02s runs at 14MHZ without a heatsink and ive seen some run faster

[kc5tja]

defzonoc wrote:

parallel is easy and if you get a real oldie like my apple 2e you can make a eeprom programmer EASY plus the guy talkin bout breadboardin a comp is silly your cpu is not TO fast as you dont have to run it at top speed now do you?

You don't have to run a 14MHz part at 14MHz. You can run it at 1MHz. But the chip is engineered for 14MHz, so its transistors swings its voltages high or low with very fast slew rates.

Those high slew rates takes high signal bandwidth (hundreds of MHz, if you must know -- just look at the signal in a spectrum analyzer). The faster the slew rates, the greater the signal bandwidth, and thus, the shorter the wavelength of RF the signals give off. So,

* With shorter wavelength, you need shorter runs to other components, lest your signal traces become antennas for adjacent signal paths.

* With higher frequencies, capacitance and inductance becomes an issue because now your signal traces are natural low-pass filters. If your signals happen to use frequencies greater than the natural filter's cutoff frequency, you lose signal cohesion, which prevents the chips from communicating properly, leading to hard to diagnose faults.

So, before you call me or Garth "silly," I strongly encourage you to either research the matter, or better yet to build your own computer, before issuing slurs and ad hominems.

Thanks.

[kc5tja]

defzonoc wrote:

the 65816 is odd as it multiplex the databus and adressbus now if you think you need 16mb addresses great otherwise its a big timewaster WDC's w65c02s runs at 14MHZ without a heatsink and ive seen some run faster

The 65816 can be run without dealing with the bank address byte -- I've done it with my Kestrel-1. It's perfectly happy running in a 64KiB address space. They also run at 14 to 20MHz without heatsinks (though they rate the chip for 14MHz, apparently many of them can be safely overclocked. Whether or not they need heatsinks depends specifically on your circuit's airflow and the specific chip you have installed. My suggestion: if you want a chip faster than 14 to 16MHz, use a MIPS or ARM architecture instead.)