[Coco] A Website For My Projects + A Neat CoCoNET Idea

[John Eric]

I currently can't host the site from my home computer (my neighbor is 13 and plays guild wars, through my wireless connection - his family doesn't have dsl which makes playing the game impossible, so I set the little fella' up through my wireless. This leaves little bandwidth for me to host a site.) A bit of searching, and I found "The Other Bob's website" and the provider seems tolerable - the ad can be "minimized" off the right side of the screen. So, I think I will use that service to host my site.

When I get home from work in the morning, I am going to begin setting up the site. The first thing I plan to post are pics of the CoCo 3 that I have just revived from the dead (see previous post).

Next, I am going to add the 1986 GIME Fix to this CoCo 3 and pictures of that. It is interesting that the 1986 GIME apparently does not properly gate the E clock and S2 select signals. This apparently caused data bus contention when the ROMs were read and caused "sparklies" and the B.L.O.B. (boot list order bug in OS-9). During research, I found two suggested fixes. The first and easiest was to replace capacitor c64 with a 220pf cap (it is originally 150pf). I've already performed this fix, but honestly, I don't see it preventing the contention when the ROMs are accessed. The actual guaranteed to work fix is to properly gate the E Clock with the S2 line using a NOR gate. In the CoCo 1, the E Clock was gated with the S2 line and used as the G2a enable of the 74LS138. This is generally how it is fixed on the CoCo 3. However, In the CoCo 2, things were done a bit differently. In addition to gating E and S2 to give G2b (yes, G2b in the 26-3026 and 26-3027
 CoCo 2's), the R/W* line was gated with the S2 line and used as the G2a enable of the 74LS138. So, I pondered, what would happen if I used this gating scheme in the CoCo 3 to enable the 74LS138? Well, I tested it and strangely enough, the CoCo 3 powers up straight into the CTR-ALT-RESET Three Musketeers screen and stays there. So this is useless. No - wait - using this circuit and making the R/W*<nor>S2 able to be turned on or off (say, using a locking keyswitch), the CoCo 3 can have a security key (once common in AT PC cases), plus the GIME Fix, and this would mean only two gates wasted in the 74LS02. I know, a keyswitch could be connected in such a way as to keep reset* low and that would do just as well for a security keyswitch, but c'mon - the three mugateers look cooler than a blank screen :). If only there were a way so that the other two NOR gates could be put to use... Oh wait, there may be - use them to increase the joystick resolution to 8
 bits. Can this be done? I haven't tested it yet in a CoCo 3, but I have tested such a scheme in the CoCo 1 with it's "discrete" dac and it works, so theoretically I should be able to get it to work in the 3, assuming the 64 collector DAC chip works the way the discrete DAC does in the CoCo 1.

Hopefully my fellow CoCo users won't get tired of my long posts, but I have so many ideas for things to build and it's so much fun. I have just finished a design on paper for a cartridge that will facilitate the use of CoCoNET with any Disk Controller. It wasn't just CoCoNET that prompted me to design this. I realize that many of you are serious collectors and may not wish to open up a cartridge thereby destroying or damaging it's label. So, what this cartridge does is:
*Contains two 2764/27128 compatible 28-pin sockets for ROMs in the CTS* range. Jumpers allow both ROM sockets to be active at the same time - BUT the only reason you would do this would be to put a ROM in one socket and a SmartWatch chip in the other. Either or Both sockets may be enabled as mentioned. Jumpers allow a 27128 to be accessed as either the full 16k or as two 8k, which means you could burn two different DOS BASICs into a 27128 and switch between them, thus allowing the pack to hold either 4 8K DOS'es or two 16k, or 2 8k+1 16k. If using a ROM in this cartridge, you would use the disable jumper (mentioned next) to disable the ROM in the disk controller that would be plugged into this cartridge.
*A Jumper to allow disabling the ROM of any cartridge plugged into this board. For example, a recent discussion here on the list involved a gentleman not wanting to open his deluxe rs-232 pack to remove the ROM. With this board, you just plug the pack into this board set the disable jumper and plug it into your multi-pack - as far as the CoCo is then concerned, the pack has no ROM.
*A Jumper to disable Cartridge Autostart. Handy for saving carts to tape, etc.
*A few more features may be added before I am done, but I have created a PCB layout for the present design and all of this will be posted on the website I am putting together over the next couple of days. This project will allow disk controllers to use a 28-pin rom with CoCoNET without having to open their controller :)

Finally, I am researching the possibility of a similar cart to above, but intended for the Speech Sound Pack. Basically, If I am successful, you would plug the speech sound pak into the cartridge and that into the CoCo. Whenever the CoCo is running at .89Mhz, the cart feeds the E and Q clocks straight to the Speech Cart, but when the CoCo is running at 1.78Mhz, the cart feeds a divided by two version of the E and Q clocks to the Speech Cart. Similar to what "The Other Bob" did, but no modification to the speech cart required. I have ordered parts to implement this and see if it works. If it fails, I will try modifying my clock speed switching circuit to function like the one here: 
http://www.6502.org/mini-projects/clock-switching/clock-switching.html
and see if that helps.

Thanks for tolerating my rant and if you guys (and gals) have any ideas for projects - throw them my way and I'll see what I can come up with.

Thanks - JEric.