Archive for May, 2011

Which Apple Interpreted Basic is the Fastest?

Saturday, May 21st, 2011

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.

VCF – great time for a vintage computer nut

Tuesday, May 17th, 2011

Last weekend was VCF east 7.0. I spent the weekend among other vintage computer nuts. It was a great time, and I highly recommend going out of your way to spend the weekend, next time this event is held. This event can not be fully appreciated unless you take the time to listen to the lectures, and see the museums that comprise the info-age facility.

Among the highlights was seeing part of an Apollo Guidance Computer, something I studied last year. I was thinking of doing some kind of recreation at one point.

Apollo Guidance Computer

Here is my exhibit, where I showed the Mimeo, A2 rev 0, brain board and PS/2 keyboard adapter. My exhibit won the gold medal in the preservation/recreation catagory.

my VCF east 7.0 exhibit

Here are the posters I displayed in my exhibit.

First the Apple 1/Mimeo poster

A1 poster

A1 poster

Second the Apple II/rev 0 poster

A2 poster

A2 poster

Note on BB assembly, Version 5.1 PROMs shipped, and Why Is the BB Upside Down?

Wednesday, May 4th, 2011

For people that still had the FCS, 4.0 PROMs, version 5.1 PROMs were shipped on Monday and should be in your mailboxes soon. I will only be updating version 5.0 PROMs upon request. The only difference between version 5.1 PROMs and 5.0 PROMs, is in the power up screen and it doesn’t affect operation in any way.

Though assembly is really straight forward, there is one thing to watch out for when assembling Brain Boards. Where the traces run between pads, the soldermask reveal extends right up to the edges of the traces and, on some boards, where registration isn’t perfect, the solder mask reveal may expose a tiny part of the trace. There is potential here for shorting the trace to the pad when soldering a component to this pad.

Brainboard-soldermask

When soldering these pads, be careful that you don’t accidentally bridge the gap between the pads and the adjacent trace. If you can’t get rid of the bridge with a solder wick or solder sucker, the easy fix is to cut the solder bridge with a hobby knife. Check continuity with an ohm meter to make sure the connection is broken.

Is the Brain Board Designed Upside Down?

It’s funny that no one has questioned or commented about the upside down layout on the brain board. This was done on purpose because of the vastly improved layout possible with upside down chips. The layout of the address and data bus connections between the 27c256 and 74LS244 sockets and the edge connector would be much more complicated if the chips were right side up. Flipping the 27c256 right side up moves the data bus connections of the 27c256 to the opposite side of the chip from the 74LS244 and Apple data bus. Also, all the lower address lines would have to be crossed to properly connect the 27C256 to the Apple bus.

Once I flipped the 27C256, I figured I had to flip all the chips and the silk screen to prevent confusion and mistakes during assembly.