steve (11/02/82)
I have owned a CoCo for over a year, and know what you need: 1. Yes you can retrofit with extended BASIC at any time, but it is cheaper if you do it now rather than later. 2. 890 KHZ is a limit that RS put in the machine so that they could use cheap PIA's. Most PIA's will run at the higher rate, they just aren't guaranteed to. You can buy ones that will do so and replace them, then by doing a "POKE 65495,0" Voila! your machine is running twice as fast. Tos slow it down again, do "POKE 65494,0". You gotta do this before doing cassette operations because the software timing loops don't work as well. It doesn't quite double your processing rate anyhow because you pick up wait-cycles when getting into the screen RAM. By the way, what you have to understand is that Motorola clocking is not comparable to that of other companies. A memory access takes 3 cycles at 890 KHZ for the 6809, but 14 cycles at 4 MHZ for a Z-80. Turns out to be about the same time. (I am referring to a LDA-type instruction.) 3. The expansion bus has the full 16-bit address, 8-bit data buss, NMI, RESET, E and Q clocks, +12, -12, +5, R/W and some signals that do other weird functions (like SND which stands for "SOUND" - it is an input into the sound-channel of the CH3/CH4 modulator). You have the ability to completely disable the 6809 or anything inside from the bus. In fact, someone out there sells a Z-80 card for it (good God!). 4. You can get lower case by buying a card for about $80 and installing it. However, what you have to realize is that you aren't going to get 80 characters wide on ANY computer with color display. There are some software packages that use the high-res graphics mode to draw truly awful looking characters, but they get 51 wide on the screen. This is the limit. 5. There are two different noise makers inside: a square-wave generator and a 6-bit D/A. The RS "SOUND" command and the "PLAY" command in X-BASIC both use the square wave generator. (The 6-bit D/A is used for all kinds of things. They use it to generate sine waves to record onto the Cassette, and it is used with an analog comparator to do the A/D on the joysticks.) If you are creative, you can generate anything you want with the D/A, but it has only one and you get to do the mixing with software - a tough job. 6. The BASIC is standard Microsoft BASIC, and as such is pretty normal. The Extended stuff has some truly nice graphics commands, and when you get a disk it adds still more. There is no standard machine language monitor, nor is there a disk monitor - instead, BASIC now knows about the disk. The word on the RS assembly ROMPACK is that it is serviceable and not particularly special. There is an extremely good macro assembler available from a company in California called Micro-works, that runs on the disk and comes with a debugger. 7. You have full ability to use the cassette for data files, however, the floppies are far more convenient. 8. The only thing wrong I have found that really gripes me is that there is no way to trap errors - "ON ERROR GOTO" is missing. This is almost a major blunder, and is always a pain in the ass. Aside from that it is a quite serviceable machine. Support for it is beginning to show up from third party vendors, because there are now a LOT of CoCo's out there (I have heard it estimated that there will be in excess of 250,000 by the end of this year). This is being accelerated by the fact that RS is introducing it as the TDP-1000 through outside merchandisers. Evidently the only difference between the 80C and the TDP-1000 is that the latter has a white case and a different number on it. If you have any further questions, feel free to ask. Steve Den Beste Tektronix [decvax|ucbvax]!teklabs!tekmdp!dadla!dadla-a!steve