Check out my Apple 1 registry for the newest entry. The most remarkable part of this entry is the letter from Steve Jobs about a possible exchange for an Apple II.
Letter from Steve Jobs
Note that a 4K Apple II board at the time retailed for $598.
Search for Fred on this page for more information about this Apple 1.
Be sure to make an effort to visit the Vintage Computer Festival East in May: http://www.facebook.com/vcfeast8
Now the trivia question.
What is the address in the silicon valley where Apple 1s were built?
To be answered in this blog in the future – post your answers in the comments section.
Mimeo 1 iPhone Case
http://crankcases.co.uk/iphone-cases-2.html
P.S. If someone asks to use an image or article, I almost always say, just credit the source and I’m fine with it.
The Brain Board review in Juiced GS included a description of a bad 74LS244. I have had one other report of problems with the Brain Board in an Apple IIe. In that second case, I had that person send back his board, twice. Though I wasn’t able to reproduce the problem in my Apple IIe with his board, I tried two different repairs, the second of which seems to be successful. The first was a simple swap of the 74LS244, which helped, but didn’t completely eliminate the problem.
After further analysis, I determined that the grounding of the 74LS244 is less than optimal on the Brain Board and switching on of the 74LS244 causes a lot of noise on the ground. Apple boards that use a similar data bus driver circuit (Apple FW card & Super Serial) also exhibit this switching noise. The stock Brain Board is somewhat worse in this regard. I found that adding an additional ground wire on the 74LS244 reduces noise to levels lower than the Apple FW board and appears to solve the problem.
This intermittent operation is typically seen as random characters input while at the console prompt, while not actually typing on the keyboard. If you notice this problem, add a wire between the ground pin of the 74LS244 and the ground lead of the decoupling cap near the other end of the edge connector.
Here is an image of a board with the fix applied.
brainboard 74LS244 ground wire fix
One more word about this problem. Though I didn’t know of any issue with the ground, when laying out the production Brain Board, I considered shortening the ground connection to the 74LS244, running it across the center of the board, instead of the top. This change might have prevented this issue. However, I decided that, since, in several years of operation of the prototype “Brain Board”, I had seen no issues, that it was unnecessary. This is a case where the “if it ain’t broke, don’t fix it” approach, was the wrong approach. For now, the one wire fix will have to do. If I make another run of these boards, the ground trace will be widened and rerouted using the shortened path I considered before.
Also because of this issue, I’m going to have to make major changes to the layout of the protoboard that I have described earlier in this blog.
Here is how I currently manage Mimeo 1 kit availability.
Even though the volume of kits sold is very low, this process is very time consuming. Just as bad for me, the effort required is very dependent on the frequency and timing of Mimeo 1 kit purchases. This makes it very hard to make consistent progress on new projects (like the Scelbi).
Check it out – done by one of the folks that picked a kit up up at K-fest.
http://www.ustream.tv/recorded/16320592
Ken Gagne was kind enough to take some Brain Boards out to K-fest and sold them at the vendor fair. Do to these extra K-Fest sales, I’ve now managed to cover my costs in producing the “Brain Board”. Thanks to everyone that has purchased one (or more) of these units.
Because I’ve covered my cost, and it might be interesting to some folks, I’m now releasing the source code for the Wozanium pack.
Also included, is a ROM file suitable for emulators, such as Virtual II. This allows you to run and debug Apple 1 software in the Apple II emulator environment. Just select the .ROM file as the ROM for your machine and reset your virtual machine. Just as in the Brain Board, right arrow will clear the screen. With Virtual II, you can download AIF files of A1 basic and assembly language programs and run them in your emulated Apple II, using the emulated cassette interface built into Virtual II. Note that this ROM version does not include the ACI driver at C100, so you must enter the Cassette driver by entering “D000R”, instead.
You can build the source with the 6502 DASM cross assembler.
Use the following command line:
“dasm a2a1emulv5_1.asm -DBLD4ROMBD=0 -DHUSTNBASIC=0 -oa2a1rbh.o -la2a1rbh.lst”
Included in this zip is
* a1basic-universal.asm – Apple 1 BASIC modified to run on Brainboard/Wozanium (note copyright at beginning of this file)
* COPYING.txt – GNU lincense for rest of Wozanium pack
* a2a1emulv5_1.asm – Wozanium source code
* a2a1emulv5_1.lst – Listing
* a2a1emulv5_1.o – Object file
* a2a1emulv5_1.rom – 12K rom file that can be used with A2 emulators, such as Virtual II.
Click a2a1emulv5_1.zip to download Version 5.1.
More about the Brain Board can be found at:
http://www.willegal.net/appleii/brainboard.htm
Looks like Eric of http://whats.all.this.brouhaha.com/ is working on a 6800 Monitor for the Apple 1. Several people have talked to me about doing this in the past, but it looks like Eric is really doing it as part of the annual retro-challenge. The obvious question is whether Eric or someone else will configure a physical clone of an Apple 1 for a 6800 and see if the hardware really works as designed.
I’ve noticed long ago that there is a significant amount of noise on the -5 volt supply on the Apple 1. The -5 power supply is connected to 16 4096 DRAMs, 7 2504v shift registers, and the 2513 character generator, 24 chips in all, spread around the board. Beside a 22UF cap next to the voltage regulator, there is only 1 .1UF decoupling cap connected to this supply.
Apple 1 - minus five noise
Here is an oscilloscope picture of this noise. Frequency of this trace is set to 5 micro-seconds/division. Top trace is -5 taken directly from a DRAM chip. Scale is .5 volts per division. Bottom trace is RAS taken from same DRAM chip. Scale is 2 volts per division. You can see that some of the noise on the -5 supply is being generated directly by RAS switching. This working system exhibits over a .5 volts of noise on the -5 supply to the DRAM chips.
Last month, while bringing up a new Mimeo 1 board, this excess noise on the -5 volt supply became a problem. This board exhibited intermittent memory write failures, with writes of zero bits occasionally failing. The bit would end up reading back as a one sometime later in time. It took me quite a few hours of debugging to figure out that the problem was due to all the noise on the -5 volt supply. The fix turned out to be a simple replacement of the single .1 UF decoupling cap on the -5 supply with a different .1 UF cap.
For those of you that don’t know, decoupling capacitors are typically distributed around boards that have digital circuits to limit surges in power demand from one chip from affecting the power supply to other components. The capacitors act as small power sources that can supply small amounts of power to nearby chips as the power demand from these chip changes due to switching logic levels. A commonly used ratio of decoupling caps to chips on a typical +5 volt TTL design is 1 decoupling cap to 2 74LSXX parts. I’m not sure what the ratio should be for -5 volt supply in a MOS design, but the Apple 1 implementation is clearly insufficient and results in a lot of switching noise on the -5 power supply.
Capacitors are rated for deviation from the specified value. Typical variations for the ceramic disc capacitors used in first batch Apple 1s are +80/-20. In order to optimize putting a higher value capacitor in this location, I built a simple capacitor tester. Future Mimeo kits will have a separately packaged .1UF ceramic disc capacitor that tested as having a value towards the higher end of the range seen. I recommend using this cap at location B13, which is the -5 decoupling capacitor.
While at the vintage computer festival, I had an Apple 1, an Apple II with integer BASIC and an Apple IIplus with Applesoft all up and running.
At one point late in the afternoon on Sunday, I decided to have a simple performance contest between these machines. This is the program.
10 FOR I = 0 TO 10000
20 NEXT I
30 PRINT “DONE”
40 END
Two machines were matched against each other and the program started at the same time on both machines. The first to finish was the winner.
After several heats, here are the results.
1st place – Apple 1 – by a little
2nd place- Apple II
3rd place – Apple II plus – way behind
At first, I was confused by the Apple 1 beating the Apple II, as the Apple II should run about 5% faster than an Apple 1. This is do to the more efficient method for refreshing memory on the Apple II. The Apple 1 stops processor clocks while refreshing, while the Apple II uses unused portions of the 6502 bus cycles to refresh memory (and read video display data). Integer BASIC on the Apple II is a direct development of Apple 1 Basic, so I was thinking that the performance would depend on the processor, not the Integer BASIC implementation, which were basically the same.
After a while I realized that Apple 1 BASIC might be a little simpler than Apple II BASIC and thus faster. I ran a second test. In this test, I booted the A2plus that I had there at the show into Apple 1 mode, with the Brain Board/WOZANIUM and ran the test against the original Apple 1. Both machines were now running virtually the same version of BASIC. In this case, the Apple II beat the Apple 1 by the expected amount. Thus, Apple 1 BASIC running on an Apple II, is the fastest version of Apple BASIC.
However, keep in mind that if print statements are added to the loop, the Apple II will beat the Apple 1 by a substantial amount.