Captain Crunch’s Memory Modification

August 28th, 2015

After I received the original snap shot of John Draper’s Apple II, I asked for and received better images. Here is one of them, showing the unusual Apple II memory arrangement.

Crunch's Memory

Crunch’s Memory

If you look closely, you will notice that all the memory banks are double stacked, largely with Signetics 2660 chips. These chips are 4Kx1, compatible with 4096s. This gives this system 24K of memory in 6 banks of 4K on each bank. Though I’ve seen double stacked memory on other systems, occassionally even on production boards, I’ve never seen this on any Apple II. Everyone else, managed to find 16Kx1 DRAMs and used those to expand their systems memmory. Don’t get me wrong, 16K memory chips were not cheap, especially in the early days of the Apple II. In fact for a long time, I ran my original Apple II with 2 banks of 16K and 1 bank of 4K for a total of 36K, which is all I could afford. I do believe John Draper’s approach is truly a unique solution to expanding memory for the Apple II.

What is more remarkable is this article, where John Draper, Capt. Crunch talks about his Apple II.

http://www.webcrunchers.com/crunch/Play/comp_rev/charlie.html

John mentions his Apple II memory configuration in the second paragraph, “My apple used the cheaper 4k rams and I piggy backed them to get 24k of ram.”

At some point, I plan on reviewing the wiring to see exactly how John wired up the 6 banks of memory.

I have more information on this system to post in later blog entries.

Apple IIe Fast Scroll Routine

August 27th, 2015

I’ve been working on improving my Apple IIe TTY emulation application. One of the major limitations with it, is the amount of time it takes to scroll the Apple IIe’s screen, especially when in 80 column mode. In order to improve this function, I wrote my own fast scroll routine. Kind of interesting how close it turned out to a comment I received to a previous post, even though I forgot about that comment by the time I did this.

;
; Fast Screen Scroll Routine
;
LINE1 EQU $400
LINE2 EQU $480
LINE3 EQU $500
LINE4 EQU $580
LINE5 EQU $600
LINE6 EQU $680
LINE7 EQU $700
LINE8 EQU $780
LINE9 EQU $428
LINE10 EQU $4A8
LINE11 EQU $528
LINE12 EQU $5A8
LINE13 EQU $628
LINE14 EQU $6A8
LINE15 EQU $728
LINE16 EQU $7A8
LINE17 EQU $450
LINE18 EQU $4D0
LINE19 EQU $550
LINE20 EQU $5D0
LINE21 EQU $650
LINE22 EQU $6D0
LINE23 EQU $750
LINE24 EQU $7D0

FAST_SCROLL
  STA STORE80 ; enable aux mem
  STA PAGE2OF ; page 1 first
  JSR FS_DOIT
  STA PAGE2ON ; now do aux mem

FS_DOIT:
  LDX #39
FS_L1:
  LDA LINE2,X
  STA LINE1,X
  LDA LINE3,X
  STA LINE2,X
  LDA LINE4,X
  STA LINE3,X
  LDA LINE5,X
  STA LINE4,X
  LDA LINE6,X
  STA LINE5,X
  LDA LINE7,X
  STA LINE6,X
  LDA LINE8,X
  STA LINE7,X
  LDA LINE9,X
  STA LINE8,X
  LDA LINE10,X
  STA LINE9,X
  LDA LINE11,X
  STA LINE10,X
  LDA LINE12,X
  STA LINE11,X
  LDA LINE13,X
  STA LINE12,X
  DEX
  BPL FS_L1

  LDX #39
FS_L13:
  LDA LINE14,X
  STA LINE13,X
  LDA LINE15,X
  STA LINE14,X
  LDA LINE16,X
  STA LINE15,X
  LDA LINE17,X
  STA LINE16,X
  LDA LINE18,X
  STA LINE17,X
  LDA LINE19,X
  STA LINE18,X
  LDA LINE20,X
  STA LINE19,X
  LDA LINE21,X
  STA LINE20,X
  LDA LINE22,X
  STA LINE21,X
  LDA LINE23,X
  STA LINE22,X
  LDA LINE24,X
  STA LINE23,X
  LDA #$A0 ; clear last line
  STA LINE24,X
  DEX
  BPL FS_L13

  RTS

This routine takes about 18 milliseconds to run on a 1 MHz Apple IIe, compared to the standard monitor scroll routine which takes 34 milliseconds. Other than unrolling the loops, which would greatly expand the size of the function for a minimal speed increase, I think this is about as fast as it’s going to get.

18 milliseconds is still not fast enough for my TTY emulation package, so I’m going to have split it up into several segments and check for input events between segments. However, now that I have my own version of the scroll code, I’ll be able to split it up relatively easily.

There are some other issues with the standard monitor COUT routines for this TTY application, so it’s very possible that I’ll end up customizing all the COUT routines. For instance, I’ve already customized the “BELL” function for performance reasons. The Carriage Return function also had to be customized, because on a teletype, CR does not force a line feed.

SCELBI Cassette Read Card Built

August 26th, 2015
SCELBI Cassette Read Card

SCELBI Cassette Read Card

Since I didn’t have information on the transistors used, I choose vanilla 2N3904 (NPN) and 2N3906 (PNP) transistors for this build. The 72741 OP-AMPs are vanilla 741 OP-AMPs in a 14 pin package. They are pretty hard to find in that package, but I did manage to snag a few off of eBay. I described where I found the yellow capacitors in a previous post. You will notice one carbon film resistor in the mix. That is because I forgot to order a 2700 ohm composition resistor, and I happened to have the right value carbon film resistor in my stash.

This card is essentially just a tone detector. I should be able to test functionality and performance and adjust it without hooking it up to my SCELBI by using a computer based tone generator application that I bought a while back. This is what I did when resurrecting the HAL ST-6 TTY terminal unit. Except for frequencies used, it basically does the same thing, though at a much less sophisticated level.

One unique thing about this board is that there isn’t a single VIA present.

SCELBI Tape Recording

August 23rd, 2015

I made this with a tape recorder this morning.

I will not be able to verify that it’s working 100% until I get the cassette read card built, but it sounds a lot like the sound of an original SCELBI tape that Mark Arnold sent me a little while back.

The format is substantially different than the format WOZ used later on for his Apple computers. The SCELBI actually uses the ones and zeros to switch output between two frequencies, instead of directly generating the waveform in software. This is very similar to how RTTY AFSK (audio frequency shift keying) is done. Though I don’t have the audio format entirely figured out, it appears substantially more complex than the Apple format, with each nibble being sent as a sort of independant packet.

First Reproduction SCELBI Write Card Built

August 22nd, 2015
Reproduction SCELBI Cassette Write Card

Reproduction SCELBI Cassette Write Card

Here’s a link to an original write card for comparisions sake.

Except for the relay, I soldered chips directly on the board. Departing from what I did with my SCELBI RAM boards, where I used NOS solder tail sockets, I used a machine pin socket for the relay. No serious issues were found during the build. I powered up and found it draws about .25 AMPs, so I put in a .5 amp fuse. The BOM I published in a previous blog entry was missing a 74121, but I had one of those on hand. I used a 2n3904 transistor to drive the relay and the schematic is missing the value for a 1K resistor. There is a place for a capacitor on the output, but none exists in the images of actual boards that I have seen, so I left it out.

I just noticed I forgot to put in the jumper next to chip Z6.

Outside of some articles in Micro-8 newsletter and some mention in other documents, we don’t have any original documentation for SCELBI peripherals. Once I get everything working, I’m going to have to create some docs for these cards.

After adding the jumper, I’ll build a cable between an edge connector and an 86CP11 connector, so I can plug it in to my 8B and see what happens. I will eventually put it and the read card in an a small aluminum enclosure like the originals had.

An Apple with a Very Interesting History

August 21st, 2015

My web site doesn’t draw the number of hits that many more popular sites do, but my site occasionally attracts some emails that turn into very interesting stories. The discovery of John Draper’s Apple II is one of them, and I need to put together a few more posts in order to describe his system and it’s history. However, right on the heels of the discovery of Draper’s Apple II, another very interesting system has just surfaced which is housed in this enclosure.

Apple Case

Apple Case

The story is that it was taken out of Steve Jobs office by Apple employee and manufacturing engineer, Don Hutmacher, after Steve was fired in the mid 80s. The story goes that Don was allowed by his boss to go into Steve Job’s office take anything that was left over. It had been picked clean by the time that he got there. He noticed this computer and a bag of Starbucks coffee, and that is how he ended up with it.

More to come…

Amazing Discovery

August 19th, 2015

In a previous post, I mentioned that an amazing vintage find has just been made. Last week, I received an email with this picture.

Apple II rev 0

Apple II rev 0

The person said, “Hi mike. I found your page via Google. Can you help me identify this apple product please? I think it is an apple ii board. ”

I receive these sorts of requests from time to time and this request for information is typical. My answer went like this:”It’s a revision 0 Apple II motherboard. You don’t find many with original 4K memory jumper blocks still installed. Almost all of them were upgraded to use 16K memory chips. Looks like someone has done some unconventional memory upgrades, but it otherwise looks pretty original. It could be a really early one, the serial number is usually written in sharpie in the white block near the power supply connector. There may be some masking tape over it.”

After a few more email exchanges that day, the person sent me an email declaring that he thought it was “Charley”. Charley is the machine that John Draper, “Captain Crunch” turned into the first phone freak computer. This machine was seized during a police raid at a housewarming party, held on 22nd of October, 1977. Here is a link to a copy of the party invitation.

There is always the danger of fraud in cases like this, but I’m pretty well convinced that this is actually “Charley”, and I’ll explain more in a future post.

SCELBI 8B Working in New Chassis

August 18th, 2015

I had a couple of issues. A poorly seated DBB card. This was followed by trouble using the extender card that Cameron Cooper and I had made a while back.

SCELBI card extender

SCELBI card extender

When the extender was added to troubleshoot the DBB card, it introduced noise on the strobe lines, which resulted in issues with my TTY interface. Removing the extender card, and properly seating the DBB card resolved all issues.

Next up: another attempt at printing the front panels and construction can start on the cassette interface cards.

Potentially Amazing Apple

August 14th, 2015

I frequently get email from people wondering about the value of an Apple 1 or II computer. Often they are ordinary systems, of little special interest, but once in a while, a gem surfaces.

I was contacted yesterday by someone that wanted more information on what appeared to him to be an early Apple computer. This was a system that his dad was about to trash. After exchanging a number of emails with this person, he thinks he discovered that this could turn out to be a system with a very special history. Now people that read my Applefritter post about that thrift shop Apple 1, know that I’m kind of skeptical about this kind of stuff. However, this one really has me excited. More coming soon…

SCELBI 8B I/O Port Wiring Completed

August 11th, 2015
SCELBI 8B Wiring Complete

SCELBI 8B Wiring Complete

I decided to wire the data output bus to the end connector rather than split between the middle two connectors as specified in the SCELBI build manual. I choose to do this primarily because of the cleaner wiring that is possible. The way the data bus is connected to all the memory cards, all the I/O ports and then to connected peripherals through long cables, leaves lots of room for transmission line issues. This concern, is probably why SCELBI recommended connecting four bits to each of the two center connectors. I’m no expert on transmission line theory, so I’m not sure whether the end connection will cause any issues that will require redoing this particular wiring. My guess is that given all the other wiring and relatively low data rate, is that it will have no measurable affect, which is why I’m trying it. The other thing about it, is the idea that I picked up somewhere along the way that branching transmission lines is generally a bad idea. I suppose I’ll have to compare my 8H which was done the SCELBI way with the 8B and see which looks cleaner, electrically.

The other thing I’ve done, is to connect the CPU SYNC clock to pin 10 of input port 3 and pin 10 of output port 3. These are the two red wires, one down the middle of the backplane, and the other from input port 3 to output port 3. Based on my examination of the SCELBI cassette schematics and drivers, it looks like this will be needed to provide timing for the cassette interface.

The last two items before moving onto the cassette interface is checking out the system, now that the I/O is wired and then, finally, screen printing the front panel. I did try screen printing a panel a week or so ago, but had issues with my screen not being stretched tight enough and I’ll have to make another one.