Archive for September, 2012

Apple 1 and Datanetics Backspace Working

Friday, September 28th, 2012

While working on a micro-controller replacement for the MM5740/AAE keyboard decoder used on the Datanetics keyboard, I discovered a way to send the unique Apple 1 backspace keycode (0x5F). You need to connect line X4 of the matrix to one lead of a blank keyswitch and Y3 to the other lead of the same keyswitch. Then by holding down shift and pressing that blank key, you can generate the 0x5F needed to backspace the Apple 1 monitor.

Note that you could also rewire the left arrow key of a MM5740 based Apple II keyboard to accomplish the same thing. Unfortunately there is no easy way to avoid the requirement of pressing the shift key to generate the correct code.

Generating PI to a thousand places with an 8008

Tuesday, September 25th, 2012

Mac OS/X users, Egan Ford sent me a PI generation program that can be run with my SCELBI emulator. Check it out at the bottom of my 8008/Scelbi page.

Apple Monitor Format to AIFF Utility

Friday, September 21st, 2012

I use this utility to convert files in Apple monitor format files to AIFF. Once in AIFF format I can download them to a real Apple II using a portable music player (iPod) and the cassette port on a real Apple II. This is the easiest and fastest way I know of, to move files to real Apple II and is an essential part of the cross development process I use for developing Apple II programs.

This version has only been tested on Intel MAC, but it was converted from a Mac PPC program, fixing endian and word length issues, so it may work, as is, on other platforms. I have a similar version for Apple 1, but it hasn’t yet been converted to Intel Mac. Here is the source for the Apple2 monitor to AIFF program.

a2aiff

SCELBI Museum Website Up

Thursday, September 20th, 2012

Cameron Cooper has put his SCELBI website online. It contains a ton of SCELBI information, some of which cannot be found anywhere else on the web. Check it out: www.scelbi.com

New Version of PS/2 Keyboard Adapter Firmware

Sunday, September 16th, 2012

I had to program a new batch of micro-controllers, so I decided to make a few minor tweaks to the firmware.

  • The data invert functionality has been dropped . If you need inverted data, you can use external inverters to accomplish the same functionality. I don’t know of anyone that actually used this feature.
  • The jumper that used to control inverted data, is now used to control automatic reset and clear. Automatic reset system and clear screen upon power up is now disabled, unless the jumper is inserted. Several Apple 1 owners wanted more authentic operation, so now I disable automatic reset and clear screen feature by default.
  • A behavior that sometimes caused multiple resets when control-alt-delete reset sequence was used has been eliminated. Once reset occurs, all three keys must be released, before control-alt-delete can cause a second reset. The control-r, control-s, control-t reset functionality is unchanged.
  • Check out the manual that is downloadable from the PS/2 keyboard adapter page.

    new batch of Mimeo’s on order

    Saturday, September 15th, 2012

    Next batch of Mimeo boards are now on order. I should be able to pick them up in about 3 weeks. Sorry for the delay, to those that I promised boards in September, but a lot has been going on here at Mimeo headquarters.

    This order was delayed, because a couple of weeks ago, I decided to investigate the possibility of using a different supplier, that would be able to work with me a little bit more. Though Advanced Circuits does fantastic work, they are set up to produce boards in a standard way. Whenever I have asked for them to do something a little different, I really haven’t received much help, or have been asked to pay for custom service, which is often more than I can afford.

    An example is the Datanetics keyboard PCBs that I had made a couple of years ago. Even though those boards have no solder mask or silkscreen layer, I had to pay standard price. Other “online” PCB fab places have similar policies.

    Yesterday, I visited a local place that I placed the order with. They took about an hour to talk to me. They even took me on a complete tour of their facility. I was pretty impressed at the complexity of the process. Anyone familiar with etching PCBs at home, would hardly recognize what is going on in a real production facility. I know I hardly did.

    Pricing was competitive. I’m taking a slight hit on a one time set up charge, but I think the personal service will be worth this one time cost.

    Stay tuned for an update as we proceed through these uncharted waters.

    Scelbi Museum Website Will Be Online Soon

    Saturday, September 15th, 2012

    Cameron and I (well mostly Cameron) has been accumulating SCELBI docs, software, flyers, images, books and information. Cameron is working on putting this online, so soon we will have a comprehensive SCELBI site available for everyone to enjoy.

    Early SCELBI Price List

    Friday, September 14th, 2012

    Check out this early SCELBI price list that I managed to obtain. Notice the address is Nat Wadsworth’s residence.

    SCELBI Price Guide

    Rod Holt’s Apple 2 Fix (part 2)

    Friday, September 14th, 2012

    Well I found some time and pulled the DRAM bus termination resistors from one of my rev 0 replicas, to see what would happen. I expected to find the machine still worked but with some erratic behavior. I planned to take before and after O’scope shots of the DRAM address bus to be able to demonstrate the difference.

    What I expected and what I got were quite different. What I got, was a machine that wouldn’t boot and give me a monitor prompt at all. I couldn’t really do before and after O’scope images, because I couldn’t generate an apples to apples comparison without putting the processor into the same tight loop for both test cases. However the display on the video was stable, so it shows that DRAM access was at least mostly working without the termination resistors.

    I tried 4K and 36K DRAM configurations, and found no difference in behavior.

    While my reproduction isn’t an original Apple preproduction board, I don’t think behavior would have been significantly different on a preproduction Apple II.

    Just to speculate a little. There may have been enough board to board variation that some pre-production units worked better than others, but I imagine that on the whole, things didn’t look very promising when the first prototype Apple IIs were built. Imagine the struggle that the early Apple employees had, finding a way to stabilize the computer enough to show at the West Coast Computer Faire, and more importantly get it in shape for revenue shipments.

    The old mac is dead, long live the mac

    Tuesday, September 11th, 2012

    It was actually a 2002 model, 1.25 GHZ dual processor MDD tower. I loved that machine, it really only started showing it’s age in the last couple of years. That machine lasted longer as my main home machine than any other I’ve had. Other contenders:

  • The next was a IIci which lasted about 7 to 8 years. The IIci was also my most expensive computer purchase – about $5000 including grayscale monitor and video card.
  • My MAC 128K lasted about 6 years (including a number of upgrades up to MAC plus)
  • I wonder if Apple will be releasing new Imac models tomorrow?