Updated Apple 1 Reproduction Flyer with Original Image from Ad

I have permission from Wendell Sander to publish a high res scan of an original print of an Apple 1. We believe that this is either the exact image used in the original ad or at least from the same photo shoot. We are so lucky that Wendell saved this very detailed print all these years, and is so willing to share it with all of us. I have updated the flyer and included this scan, which pretty much makes this reproduction about as good as I can make it, at least in available time. I left the image uncompressed, in case you want to blow it up to poster size.

Ad with high res image

enjoy…

CFFA 1 back in stock

It appears that Rich Dreher have made another batch of CFFA 1’s available.

http://dreher.net/print.php?s=projects/CFforApple1

I have tested these in the Mimeo and they work great. If you are tired of dealing with the cassette interface or a serial port (on PS/2 adapter), these are great way to load programs into your Mimeo.

The CFFA 1 also adds in extra memory, so you can run the some of the larger Apple 1 programs that are available from Wendell Sanders web site.

Do note, that in order to preload the compact flash with Apple 1 software on a PC, I think you need to use a Windows program called Ciderpress. I don’t know of a Macintosh equivalent. You can always load the program on the Apple 1, using my PS/2 adapter’s serial port, and then save to the CFFA 1. CFFA 1’s use the Apple 1’s slot, so unless you have a slot expander, you can’t use both an ACI and CFFA 1.

Say Hi At VCFse in the Atlanta Area

This year, for the third year in a row, I’ll be leaving the family in the care of our dog, Toby, and be spending a weekend with fellow retro-computer hobbyists. Since this years VCFeast, had to be cancelled, I’ll be treking down to VCF southeast in Atlanta for the weekend of April 20 and 21st. These weekends are always fun, so I highly encourage everyone that might be interested in these things to make the effort to join us.

Here is the link with informaiton for that event.
http://vintage.org/2013/southeast/

Stop by my exhibit. I’ll be operating a Mimeo 1 and a reproduction SCELBI 8H (one of a very few working SCELBIs in the world). I’ll even give you a chance to “drive”. Tell me you read my blog and get a free SCELBI/8008 reference card.

See you there…

PS/2 Adapter Repurposing

The daunting task of toggling in a program of any significant length into a SCELBI has made me consider ways of automating the process, at least for demonstration purposes. What I’m looking at, is altering the program on one of my PS/2 to ASCII keyboard adapters and connecting it to the SCELBI’s front panel connections. Here are the reasons why I think this will work out really well.

  • The front panel is controlled through TTL I/O lines pulled up to +5 volts with 1k resistors. This is something that the AVR should be able interface directly to.
  • There are more than enough I/Os available on the PS/2 card, especially if I repurpose the three configuration jumpers. There are 8 bits for data and three pushbuttons for control. In addition I should be able to tap into a couple of the CPU status lines in order synchronize with the CPU states.
  • I already have both keyboard and RS232 drivers written for this board.
  • The keyboard can be used for control and the RS232 port to get data from a host computer.
  • An alternate approach is to use RS232 for both data and control.
  • I have plenty of these boards available. I’ve used less then half of the lifetime supply that I had made when the Mimeo first came out.
  • The interesting thing about this little board, is that I can also use it for other interface applications on the SCELBI, at least until I have time to reproduce authentic 70s era interfaces that were available. Examples include:

  • RS232 interface
  • With a bit of extra hardware – cassette tape interface
  • 6800 running on a Mimeo 1

    For a while now, we have speculated about how well a 6800 would really work in an Apple 1. Well, a 6800 is running now on a Mimeo. See Lionel’s utube video for proof.

    Eric Smith had previously created a 6800 Apple 1 monitor that he ran in emulation. Lionel took that monitor and went to work to make it run on real hardware. Lionel had to make two changes to make it work.

  • the 6800 7404 had to be changed to a slower 74L04 in order to make clock timing work
  • pin 39, which is not connected in a 6501, had to be pulled down to ground with a 10K resistor
  • Kudos to Lionel for making what I think is an Apple/Mimeo 1 first…

    More on Apple 1 -5 Volt Supply Issues and a Solution

    My friend Lionel, from Australia, reports to me about an issue with DS0026 clock driver chip on his Mimeo build. The Apple 1 was originally designed with a DS0025 clock driver chip, but the DS0026 should be a compatible replacement. The DS0025 drive a pair of clocks that are used for shifting video data through the 2504 shift registers. This clock low level is -12 volts and is the same clock that is coupled to video output and causing the video dot problem described on my Apple 1 Hardware Notes page.

    After doing some investigation, Lionel and I have determined that the 2504s are coupling this clock
    http://www.willegal.net/blog/?p=1623 onto the -5 volt supply. This is what is causing a large part of the noise on -5 volts and manifests itself as intermittent DRAM problems (failure to pass memory tests).

    Lionel has tested a fix that involves adding decoupling caps to the -5v supply in the area of the negative supply regulators and around the 2504s. Here is Lionel’s report:

    Hi Mike,

    Good news!

    It definitely looks like decoupling the -5V on pin 4 of the 2504’s is the way to go. I’ve added some 0.1uF caps to GND across both the negative regulators, and one on pin 4 of the group of four 2504s at D4-D5, one on the pair at D14, and one on the single 2504 at C11. This cleans up the -5V rail substantially to the point where using the DS0026 works! See attached photos for how I added the capacitors.

    Before I did the mod I had a look at pin 4 of each of the 2504s and there was an unbelievable amount of noise on them. It was far higher than what was across the -5V decoupling cap near the RAM. In fact, on the 2504 at C11 there was about 4V p-p of noise, when using the DS0026. I think the switching current of the 2504 must be very high, which in conjunction with the inductance of the traces on the board gives a lot of ringing.

    I’ll leave my Mimeo running for a while to burn in and check stability, but so far so good.

    Let me know how you go if you try it.

    Regards,

    Lionel…

    Here are a few pictures showing the caps added to the back of the board.

    2504D4D5

    2504D14

    2504C11

    Before Lionel came up with his solution, I tried a fix that involves adding .0022 UF capacitors between the clock outputs of the DS0025 and +5 volt supply. That also helped by softening the edges of the clocks. Lionel’s solution is much preferable, though my attempt did greatly reduce the extent of the video dot problem.

    Lionel says Unicorn shipped the DS0026 with the Mimeo parts kit. After contacting Unicorn about the problem, Lionel says that Unicorn has promised to send a replacement DS0025.