[83] Great!

[Mike Naberezny]

Hello everyone,

I have to say that I am very pleased to see a rise in activity on the forum. It seemed to lull out a bit for a time but I am quite pleased to see new faces and good content.

I have been very busy in the months following the completion of our order for 65Cxx chips from WDC. I accepted a new job and even moved to another state. However I'm mostly settled now and I should have more free time to devote to expanding the site and getting some projects off the ground (especially "Iteration 1", it has not been forgotten).

As always, send me any comments or suggestions you have for www.6502.org. I have been busy makes changes and additions to the site, most of which you probably won't notice but many of the links have been fixed and some have been added. There's also been a good sampling of code submitted to the Source Code Repository (please send more!).

Best Regards,
Mike

[AndyB]

Hi Mike!

MN> I should have more free time to devote to expanding the site and getting some projects off the ground (especially "Iteration 1", it has not been forgotten).

That's great to hear Mike, be sure to let us know when they become available!

Regards,

- Andy.

[trmelton9]

Good to hear from you. I had a very busy few months at work. (80 hour weeks really kill you.)
I missed out on your bulk order from WDC. And I haven't seen much on the SBC design. The last few weeks I've been trying to catch up. Over the holidays I went back & re-read all of the posts on the design.

I've got it all entered in OrCAD except for the battery backup on the RAM. I haven't got upto speed with Eagle, yet. But I don't think the free version will allow a board large enough. By the way, I saw a magazine add that Eagle has a new update.

While working on the schematic, I thought of something else. The max speed of the board is 4 MHZ. This requies a EPROM of about 120 nsec access. This is fine with the newer 27128 & 27256 chips, but if anyone whats to use 2716 or 2732 or 2764 chips that they have there'll be a problem. Do you think there should be a wait state generator to allow slower EPROM's.
Ted Melton

[GARTHWILSON]

This is sort of off the 6502 subject-- but,

How does the Eagle CAD do? I got a demo disc some time back, and they guarateed that this thing was quite bug- and crash-free. Well, the demo itself crashed on me.

I used OrCAD years ago at another job. It had more bugs than an ant hill. I know they've re-written everything, but unless they've made a dramatic overhaul of their whole programming philosophy, I wouldn't expect a whole lot of improvement.

I've been using Easy-PC Pro from Number One Systems in England for the last seven years. It's quite inexpensive, and their latest DOS version (from '95?) is relatively bug-free, and lives up to its name. It's quite flexible and doesn't try to tell you that you can't do certain things if they don't fit the expected pattern. The non-professional version was only about $175 and would run on virtually any DOS computer, even an 8088 as I recall, and is quite suitable for the hobbyists on this forum. It was quite fast, being written in assembly. I expect it's still available from Ohio Automation in Athens, OH.

About the EPROMs-- Is there any reason to use the older, smaller, slower ones you mention if newer, faster (100 or 70ns) ones are so inexpensive?

[trmelton9]

I've got the Windoze Version of the Schematic Capture & the last DOS Version of the PCB Layout. I really love the Schematic Capture. It's very friendly & easy to use. The PCB Layout seems to work fine. I've done several boards with it down to some tiny SMT boards.

There's really no reason for the slower EPROM's, except I have few bins of them & I thought some of the other people in the group might, also. Just a thought. If at some point we try to get upto 10 - 20 MHZ with a 65816, won't we have to do something to use ava. EPROM's ?
Ted Melton

[GARTHWILSON]

I don't know of any PROMs of any kind that are fast enough for 10-20MHz systems, do you? A look at IC Master's website netted me nothing (but then, it doesn't seem to be a very friendly website). I've looked at a few different ideas for getting the tiny boot program into fast SRAM before starting the uP, and I'm tentatively looking at keeping the uP tri-stated while a PIC or something else takes over the busses to load that in. Then it will have enough to load the operating system from a large serial flash or whatever. Address decoding will be simpler then too.

[trmelton9]

No, I don't know of any EPROM's fast enough. What was used in the old S-100 Bus systems was a "wait state generator". It would hold "RDY" for one or two clocks to allow the "EPROM" to respond. I had thought of using something like this & what the PC motherboards call "Shadow RAM". Boot up with slow EPROM, copy itself to RAM, switch off the EPROM & then run from RAM. It gets pretty complex, but to get to full speed, maybe OK. The WDC 65C265 has two clocks to allow for something like this. Also, some of the Mitsubishi chips (6502 like) had dual Clocks.
Ted Melton

[GARTHWILSON]

One of the things I had considered was some extra logic in the clock circuit that would stretch the phase-2-high time by skipping a low time under the prescribed conditions. In other words, the ending clock frequency would be cut in half (for as little as one cycle at a time), but the extra time all went into the phase-2-high time, leaving the phase-2-low time unchanged. You could probably figure it out from there if you haven't already, but if not, let me know and I can fax you the logic diagram or post some VHDL code.

[trmelton9]

Somewhere I've got a app. note from Rockwell on how to do that. I'll try & dig it up.
Ted Melton