Archive for April, 2011

Version 5.1 Brain Board Manual posted on BB page

Thursday, April 21st, 2011

The only difference between version 5.0 and 5.1 is the power up screen. The original A1 had alternating “_” and “@” signs with the @ signs flashing. The @ signs actually disappeared during the flash off.

With version 5.0, I had the @ signs flashing between normal and inverse instead of completely disappearing. With version 5.1, this was fixed to have the @ signs disappear during flashing, like on the original Apple 1. I actually had it right on earlier versions, but made a change to dramatically improve initialization time in version 5.0 and created this discrepancy at that time.

I’ve been shipping 5.1 since 4/1/11, and have heard no reports of issues. In fact, other than the flashing @ signs, I haven’t heard of issues with any of the versions, other than someone verifying the memory corruption bug with 4.0, that I previously reported in my blog.

Because the difference is pretty small and does not affect operation in any way, I don’t intend on automatically shipping updated 5.1 PROMS to those who already have 5.0 PROMs. If you have version 5.0 you can request an update or if you have a PROM burner, I can send you an Intel hex file with the new image.

There are still a few people with version 4.0 that I owe an update to – I plan on shipping version 5.1 to you around the end of the month.

A2 Hobby/Proto Board Evolution

Wednesday, April 20th, 2011

This PCB layout is now in it’s fifth major revision and counting. Here is how it’s evolved.

A2 Hobbyboard Layout


1) A direct copy of Apple’s Hobbyboard. Many years ago, I used one of these cards to build an A/D interface with temperature sensor. This layout is ideal for prototyping with wire-wrap technology, but not so good for point to point wiring, which I prefer these days. So I moved on.

A2 Shutter Tester on QRC proto board

A2 Shutter Tester on QRC proto board

2) A direct copy of a Quality Resarch Company (QRC) Apple 2 computer prototype board. I used one of these a few years ago to build a prototype shutter tester. This board is ideal for point to point wiring, but I have decided it would be neat to build into the layout some basic I/O components like space for a 2K PROM and data bus transceivers.

The first proto design of my own making

The first proto design of my own making

3) This led to the first of my own designs. I incorporated space for a bus transceiver, a 27C256 EPROM, a SPDT switch and a DB 9 connector in this one. I used the 27C256 instead of a 27C16 because they are easier to find and cheaper, despite the fact that it has 16 times as much memory than is really needed. However, the handing of the I/O strobe for the 2K memory exansion space is kind of messy. On Apple’s super serial card, it takes 4 74LSXX series chips. This would require a lot of wiring and take up a big piece of the proto area. For these reasons, I decided to put this logic in a PAL or GAL and include the wiring right on the proto board, which leads to my next design.

My Second Proto Design

My Second Proto Design

4) In this version, I removed the toggle switch, thinking that it was not really that useful an idea. I was thinking I wanted the capability of interfacing an AVR micro-controller, while some other folks thought that a design that supported classic chip would be more appropriate. The 6522 VIA is a classic 6502 family part and includes some neat features including built in timers. I also switched from using a 27C256 to 28C256 flash part, so that it could be programmed in place, without the need for a PROM programmer. All along, I’ve wanted the capability of supporting that AVR on this board, but supporting both a micro-controller and a VIA seemed kind of awkward on the same layout.

Third Proto Design

Third Proto Design

5) My current layout tweaks the previous by making the half of the 6522 that is used for input/output pins a little more generic. The 6522 will still drop right in, but if something different is desired, then you just need to connect the bus interface to the proto area the way you want it. It is fortunate that the 6522 was set up with the I/O ports on one side of the chip and the bus interface on the other. In some ways, the 6522 VIA bus interface is just about an ideal generic A2 interface device. You have the system clock, the device select signal, read/write, interrupt, the data bus, and the four address lines that will address all 16 locations in the device select region of each slot. If you need some other bus signal, it can always be picked up off of the pads near the edge connector. One of my next challenges is to see if I can interface an AVR micro-controller directly to this bus, without additional components.

This design is not done evolving, but at this point, I think I’m happy with most of the major design decisions. I have plenty of FLASH memory for the program, a 6522 VIA for hardware interfacing and DB-9 for connection to the external world. With the 6522 in place, I have space for 4 16 pin chips, an 8 pin chip and plenty of discrete components. Yet the 6522 could easily be replaced by something else, like the AVR I keep thinking about.

One thing that might change is the DB-9, which takes up a lot of real estate. A KK type header like the one used on the super serial card is likely to replace it.

If you have ideas or opinions on this hobbycard design be sure to let me know. The more input I get, the better this card is likely to become.

Rising Ebay Prices for Apple II Systems

Monday, April 11th, 2011

I’ve noticed a trend in rising prices for A2 systems on ebay. I usually buy parts machines when I need a new system or components for a project. In the past, I’ve been able to get parts A2 plus systems (often with a lot of extras) for around $50 plus shipping.

Within the last week an A2 (not plus) system listed as parts or repair went for $810! Granted, this system had a few desirable components – but still…

An A2 plus system also listed as parts or repair went for $183.49!

Also, I’ve seen several A2 plus systems go for close to $300 lately. These were not parts systems, but it’s not long ago when that was the expected price for a non-plus system.

Is this a temporary situation, or is the day of the dirt cheap, $50 A2 plus parts system, behind us?

At least IIe’s are still dirt cheap.

Apple II hobby/prototyping board manual

Sunday, April 3rd, 2011

here are scans of all eight pages. Someday maybe I’ll find time to OCR and put it into PDF format.

hobbycard page 1

hobbycard page 1


hobbycard page 2

hobbycard page 2


hobbycard page 3

hobbycard page 3


hobbycard page 4


hobbycard page 5

hobbycard page 5


hobbycard page 6

hobbycard page 6


hobbycard page 7


hobbycard page 8

hobbycard page 8

How many original Apple 1′s are left?

Saturday, April 2nd, 2011

Well 32 are clearly documented in my registry.

Another 4 are listed on the registry page, as most likely to exist, but since I don’t have good enough information to eliminate them as duplicates, I have them listed as probable.

I have less concrete information on 4 or 5 more. Some of these may be listed soon, as the owners are planning on providing more details to me in the near future.

That puts my count of probable units at around 40. Keep in mind that I’ve only been investigating this for about a year and a half.

How many more are in private hands? That is anyone’s guess, but I’m sure that a number of owners don’t want to publish the fact that they own a collectible computer that could be worth as much as $200,000.

It wouldn’t surprise me if the number of undiscovered units was as high as 20 or 30. That means the previous estimates of under 50 remaining Apple 1′s is probably low and the actual number could be as high as 60 or 70, perhaps even more.

On the other hand, maybe everyone who has an Apple 1 has had something published on the web about it and there are only 40 left. What do you think?