Apple 1 chip reproductions

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Apple 1 chip reproductions
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There are several chips in the Apple 1 that are not very available nowadays, so it seems wise to provide reproductions for them. The chips might include:

- PROMs
- Signetics 2504, 2513, 2519
- 6502 with ROR bug
- DS0025 clock buffer

The generic TTL parts will probably have good availability for quite some time, so there's no need to worry about those.

In low volume, one way to go is a small DIP-sized PCB with an FPGA and any appropriate power and signal-voltage translation. This would plug right into the target socket. As a start, I've done the HDL and PCB layout for a PROM board, available here:

https://github.com/pmonta/retrocomputing

Attached is a screenshot of the board and a schematic PDF. You can see the holes for the 16-pin DIP pins along the edges of the board; eventually it might be nice to replace these with a DIP lead frame (tin-coated 260 brass?) that would offer more realistic pins.

This is a work in progress and nothing has been tested yet. I've sent off the small boards to OSH Park and should get them in a week or so. There might be showstopper errors in it.

I've also included in the github repository the schematic and layout of the Apple 1 cassette interface. That is also untested (I don't have an Apple 1 yet). If someone wants to fab and assemble one of those and test it in an Apple 1 replica, that would be great. I would suggest the ENIG finish for a prototype board---it's not as durable as electrolytic hard gold, but should be fine for a quick look.

Cheers,
Peter

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Chip reproductions or substitutes ?

Hi Peter,

 

I understand your pain with the obscure chips every 1st time builder of an Apple 1 replica faces.

I am currently bringing up my own Apple 1 build, which still has some quirks, but the stay-at-home orders due to this virus pandemic certainly helps to provide the spare time to sort them out.

Here is my take on the parts situation:

PROMS - I don't have any programmed ones yet, just ordered a Data I/O programmer on Ebay hoping it works. But I have close to a thousand of various 256 x 4 bit PROMs in stock, although the MMI ones may be only half a dozen, if I can find them. My build currently runs with an adapter card that plugs into the PROM sockets and carries a 2732 EPROM with various diagnostics besides the WOZmon.

Signetics 2504 can be replaced with the generic 1404 type shift registers, which in the 1970s were made by many manufacturers. I used MM1404AH made by National Semiconductors. Several brokers have them. The key here is that several builders should team up and buy a bunch so as to get better prices.

Signetics 2513 character generators: I have a full tube of them and might part with some of them.

Signetics 2519 40 x 6 shift register: very hard to get, I used 2519N I bought for a usurios price from a broker. But they are still out there and only one is needed per build. There is a 4XXX CMOS part out there, still being made, which is a 64 bit x 1 shift register whose length is programmable. At the moment I am on the road and can't recall the exact part number. Six of them could replace the 2519. Using the SMD version of these CMOS chips, a small PCB replacing the 2519 could be hidden at the backside of the Apple 1 board.

DS0025 can be replaced by the more readily available DS0026  if you put 100nF SMD bypass capacitors directly on its -12V/+5V pins to GND. The bypass caps C5 and C6 on the board seem not to be sufficient (traces too long ?)

6502 with ROR bug ? Who would want a buggy CPU that does not run most 6502 code ? Seriously ?

Anyone interested into building an "authentic" looking Apple 1 replica (or repair an original) should also look into the grind top surface away / reprint new type code and manufacturer logo by rubber stamp, as the Chinese chip counterfeiters do.

Alas, just a look at the PCB would immediately reveil it's a faked Apple 1.

But other than the 2519, and the ROR bug, everything is still available.

Anyone interested on more info can contact me via my applefritter account.

Disclaimer: the above parts replacements may have contributed to my Apple 1 build being somewhat quirky. But the more I look into it, the more I think the Apple 1 never was a stable and robust design, the PCB 'ringing' everywhere possibly being the culprit for most of those grievances. Maybe we should go to a four layer board that retains the original layout on the visible top and bottom layers and adds a sound ground plane and a good power suppy grid on the invisible inner layers.

 

 

cjs
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ROR bug

Did the original Apple 1s built by Apple have the ROR bug? The fixed CPU was released no later than May, 1976, if the date on the datasheet documenting the ROR instruction is any indication.  From the story about about  the Byte Shop units and getting the parts on 30 days, that means they didn't get the 6502s from the supplier until around June 1976, which makes it plausible that they may not have had the bug. (I've asked about this, but gotten no firm answer. Maybe someone here with an original could do a test and post about it?)

I too also wonder about the value of producing a modern 6502 replacement with the ROR bug. Software written with the ROR bug in mind won't work any differently, so the only difference would be that software that uses ROR would break, rather than run, right?

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Yes they did.   Only the last

Yes they did.   Only the last boards out of Apple had a fixed CPU.  This is one reason Mike Willegal has to make a special version of his memory test software which would run on original Apple-1 boards.

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Making Components
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UncleBernie wrote: PROMS - I
UncleBernie wrote:

 

PROMS - I don't have any programmed ones yet, just ordered a Data I/O programmer on Ebay hoping it works.

 UncleBernie,

Did you ever get that programmer to work? I am doing a build and currently in need of the mainboard PROMs and the Cassette Interface PROMS.

Anyone else know a source for PROMs?

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PROMS

You can buy the PROMS from Newton Mike via EBay (Newton-Computer) mine are working perfectly! If he does not have a offer online you may contact him and ask. That's what I did. Best regards. Denis 

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PROMS

Mike may stilll have some Newton Boards (great quality!) and the ACI including the ACI PROMS

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About the Apple-1 PROM situation ...

... actually, I provided so many programmed PROM sets to Newton Mike that I ran short of them a few weeks ago myself and had to stop selling my PROM kits on Ebay. I need all the remaining stock of blank PROMs I have for my complete IC kits.

 

The issue is not scarcity of blank PROMs. They are abundant and the 256x4 types can be bought quite cheap from chip brokers who still have many thousands, if not tens of thousands, of them in stock.  The issue is actual demand from Apple-1 builders and the minimum order size of the chip brokers. If I would buy 250 blank PROMs at once, I could get them below $2 each and even when factoring in the costs for buying (and fixing / and calibrating) my Data I/O System 19 programmer, I could sell finished PROM sets of four for below $30, free shipping.

 

But here is the catch: what if I order 250 PROMs and then can sell only a dozen more finished PROM sets  to the worldwide Apple-1 builder community ? As I try to avoid making profits (which has to do with Atlas Shrugging / Going Galt and me having more money then I want to have, it's a curse, actually, seeing it losing purchasing power month by month due to fraudulent unsound fake toilet paper "money" being "printed" by the government faster than I could earn more if I still would be stupid enough to work in my job which would make measly six figures per year, and not even a "bar") but as a matter of my iron principles also to avoid losses,  and to avoid waste of precious rare ICs, I must be careful not buying stuff I could not re-sell again over a useful period of time.

 

Put into simpler words, if I knew the Apple-1 builder community would continue to buy PROM sets in the numbers I would need to justify to buy 250 or 500 blank PROMs (amount would depend on minimum order value of broker), I would just go ahead and buy them and put them up on Ebay again.

 

Can I take that risk ? Money wise it's peanuts for me as I blow through that amount of money if I fly a private plane for just two to three hours (depending on its thirst for AVGAS). I won't starve or become homeless for wasting $500-$1000. But feelings wise it's a problem because if I can't sell them I would get angry and curse  every single time I would stumble over that useless bundle of tubes containing blank PROMs I could not even sell anymore even when blank (chip brokers won't buy them back at a good price, if they would buy them back at all).  If have lots and lots of such useless stuff I curse and get angry about my own stupidity of buying that stuff. It's terrible !

 

In the past I did not face that condundrum because there was an electronics surplus shop downtown Colorado Springs where I could buy single tubes of PROMs for a good price. The only risk I had with them was they they may not all be blanks ... so I ended up with a pile of useless ones, too. But when factoring everything together, including the losses due to the non-blank ones, or the duds, I still could sell a set of four PROMs on Ebay for $36.50 including shipping to the US. I'm still in the hole money wise due to the costs for the System 19 needed to program them, but if I could sell 100 more PROM sets (stand alone or in my complete IC kits), then I would have closed that hole and still have a nice, refurbished and calibrated System 19 as a bonus.  I also did get my big blue electrolytic capacitors from there, also at a good price. Alas, this shop went out of business last October or so:

 

So now I would need to play according to the rules of the chip brokers. The actual blank PROMs from them are cheaper per piece, at least for the 256 x 4 types, but as explained above, they want me to buy much more of them than I want to buy, not knowing how many Apple-1 builders needing PROM sets are out there.

 

I see the pain, as I regularly get messages on Ebay asking me to put some PROM sets up again, but not enough of them to justify buying 250-500 blank PROMs.

 

So far I see only one possible way out, and this is selling PROM sets based on 512x4 PROMs, from which I still have plenty in stock (I bought a bundle of tubes just a few days before OEM Parts closed their doors). Alas, the replacement price for these 512x4 types the chip brokers ring up is around $10 per piece. (This of course helps with meeting minimum order value for much smaller numbers of ICs, oh the irony).

 

I figure I could sell a Apple-I PROM kit based on 2 pcs 512x4 PROMs for A1,A2 locations and 2 pcs 256x4 PROMs for the ACI for $49 (or even somewhat less, depending on how many duds / non blank ones I will find). This is much more money than I would want to spend on such a PROM set myself. So would there be takers ? (BTW, the other half of the 512x4 PROMs would contain my proprietary burn-in software I use in my burn-in rigs, as a bonus, to sweeten the bad taste of the higher price. It includes a very good DRAM test and a complete terminal section test, and for sure would be useful for most Apple-1 builders. No mods to the Apple-1 needed to access / use this added firmware. It's essentially my DIAGNOSTIC PROM firmware except for the ram-less hex monitor, as seen in this thread: https://www.applefritter.com/content/announcing-novel-diagnostic-prom-set-apple-1-builders)

 

Actually, I did buy these 512x4 blank PROMs in anticipation of a huge demand for my DIAGNOSTIC PROM SET, but this demand never materialized, so to the Big Graveyard of  Dead Projects it went. Like many others of my projects over the past 40 years. I came back one night to steal some organs which, similar to Dr. Frankenstein's method, went into my BURN-IN firmware without much programming effort.

 

Now my long and convoluted story about Apple-1 PROMs having been told, it's up to you what I might do for you in the future. Just tell me what kind of PROMs you want, and maybe how many Apple-1 builders are out there (your guess, I never visit Farcebook oder other nasty spyware sites),  and which price you are willing to pay (no obligations), and maybe I get a more complete picture what is going on in the Apple-1 builder scene and go ahead with providing PROM sets to the Apple-1 builder community.  Keep in mind that despite I try to avoid evil profits, I don't want to make any losses neither.

 

Comments invited !

 

 

 

 

 

 

 

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UncleBernie, Too bad about

UncleBernie,

 

Too bad about your shop :( I for one would definitely be interested in the diagnostic PROMs as a deal sweetener. I guess I will hit up Mike for now and see what he has. Thanks for the replies. I am very excited about this project!

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