Video RAM Access Kit

[Gil Kloepfer Jr.]

Having purchased and assembled two of Brian Botton's video RAM kits (one
for Lenny and one for myself), I thought I would make some comments about
the kit for prospective buyers:

First, my compliments to the chef(s) on the quality of the circuit board
and kit in general.  The PC board does NOT look like bargain-basement
quality, and is, in fact, one of the BEST I've seen.  The board is even
silk-screened on the trace-side to prevent tarnishing and corrosion of
the traces.  All holes are drilled-out to their proper diameter, and
all parts are properly placed on the board.  The only exception to
this was that of the wire to be connected to pin 26...but after careful
thought, I also discovered that Brian did this because it was the ONLY
good way to do it.  One thing I would have asked would be markings
on either the trace side or component side to indicate pin 1 of the
68010 and PAL ICs.  There is plenty of space on the "copper" side to
do this...it really should have been done.

As those who know me well probably know, I hate reading instructions.
I can't comment on the parts which say how to open the machine and
get to the motherboard (although Lenny did read it and said it was
written very well).  I can say that, overall, the instructions for
assembling the PC board were good and well-supplimented with diagrams
(which made my life easier!).  Two things which I found disappointing
about the manual-- There were no PAL equations or theory-of-operation
sections.  I believe lots of this was posted to the net, but I feel
that it should have been included, one way or another, in the manual.
A schematic would also have been helpful, although the PC board can
be EASILY traced (the schematic is trivial).  Anyhow, using the
instructions as only a quick reference, I had two boards assembled and
running in less than an hour!  Again, had it not been for the excellent
quality circuit board, the soldering would have been a nightmare.

In general, the quality of the other parts was excellent.  I have one
question .. in conflict with the instructons.  Specified in the parts list
was a 0.1uF capacitor, presumably as a bypass capacitor.  The instructions
treat the capacitor as though it were a disc capacitor, and can be
inserted any directon.  In both kits I assembled, supplied was a
tantalum electrolytic capacitor (almost looks like a 1uF, rather than
0.1uF).  Electrolytic capacitors have a "+" sign near the leg that
is supposed to be connected to positive.  I knew this, and knew
enough about the PAL to know which leg should be in which hole, but
others wouldn't know about this.  For those with kits that have a
tantalum electrolytic, the "+" leg should be inserted in the hole
closest to the 68010 pins (ie. the lower one).  Failure to insert
the capacitor properly could cause damage to the capacitor.

In summary, I felt overall comfortable with the quality of the kit and
recommend that everyone who can solder (or knows someone who can) get
it.  Even if you never plan on porting X-windows or some other window
system to your machine, it greatly increases the flexibility of the
UNIX-pc at minimal cost.  In addition, the board looks like it BELONGS
in the machine, as opposed to haphazard motherboard hacks which can
be hazardous for beginners.  Good job!

Following my .signature is a *HACK* I did to test the board.  It turns
all the characters on the screen upside down.  I thought it was a fun
way to test the board, and hope you do too ;-)

Gil.

-----
| Gil Kloepfer, Jr.
| ICUS Software Systems/Bowne Management Systems (depending on where I am)
| ...icus!limbic!gil   or    gil at icus.islp.ny.us

-- Cut Here -- -- Cut Here -- -- Cut Here -- -- Cut Here --

main()
{
	unsigned short *video, *vidptr, *revptr, *revvideo, save;
	int i, j, k;

	video = (unsigned short *)0x420000;
	for (i=0; i<29; i++) {
		vidptr=video;
		revvideo=video+495;
		for (j=0; j<6; j++) {
			revptr=revvideo;
			for (k=0; k<45; k++) {
				save = *vidptr;
				*vidptr = *revptr;
				*revptr = save;
				vidptr++;
				revptr++;
			}
			revvideo -= 45;
		}
		video += 540;
	}
}

[End of program]