80-Bus News

the usual &FF.​This would explain why the new BIOS does not interfere with extension memory boards on pages other than page zero, in the Gemini/RAM B paging system. Anyway, when I get the chips together and get it all going, I will have a nice tidy 64K system with an equally tidy 256K virtual disk. When that is done, I intend to produce a couple of file updating programs in Pascal, so that I can produce some sort of “bench-mark”, and give you some indication of what sort of difference these changes make to the speed of operation of the system.

‘Pluto review’, he said casually.

I don’t know where the money for all this stuff is going to come from, but I have bought it anyway! Unlike MAP 80, IO Research took quite a while to send my Pluto out, but then they do say that the board is selling like hot cakes. It is even being sold to the makers of non-80-Bus computers, for use as a graphics unit on their bizarre (i.e. non 80-Bus) computers. I did try asking for an OEM discount, but it did no good at all. I bet you thought all the hardware manufacturers would be sending out free boards to likely reviewers, in order to get favourable reviews printed. Well, it may be like that in glossy magazine land, but there ain’t no free lunch out here in amateur land, yet! (Of course it is a hint, Mr Manufacturer, of course it is.)

Anyway. The board is of a high standard of construction, and all those things I would write if I thought you wanted to be told. Come on now chaps! Anything that costs this much is going to be of a high standard, or you would have heard rumours to the contrary. What you get is eight inches square, green, and packed with components. There are three rows of RAM chips, making 192K, an 8088 processor, TTL chips galore, and something with 40 pins whose function is unknown to me. The latter is probably some sort of video controller chip. [Ed. – a 6845 CRIC chip, as used on the Gemini IVC and Nascom Avc.] Then there are two connection plugs at the outer edge, one with twenty pins, for connection to a colour monitor, the other with fifty pins (I think) which is for connection to the Pluto Palette, when it appears. Also supplied is a manual. This is somewhat terse in its explanations of quite complicated matters. The pages are not all in the sequence you expect, there being appendices in the middle of the text. There are two example programs, one in BASIC, one in assembler, but they don’t do a lot. The most useful thing in the whole slim volume is a table of all the control codes the board accepts, listing all the parameters they need, and what values they return. Sounds like Pascal, doesn’t it? A nice touch in the manual is the way the routines are described, with headings that look like Pascal procedure and function headings. This has made me start thinking about producing some sort of software package to interface Hisoft Pascal to the Pluto, along the lines of a little known utility called Vortex, that I cobbled together a while ago. This time I won’t have to write a line drawing routine, that’s for sure! The manual also tells you how to connect the board up to a video monitor, as long as you know which connection is which on the monitor! No, it isn’t always obvious, that would make life too simple. Just to make life more entertaining, I managed to wire mine up wrong, but failed to destroy my nice colour monitor. See later section, for a very relieved review…

As far as your computer is concerned, the Pluto is just two ports (similar to the Gemini IVC), normally £A0 and £A1, although these addresses can be changed if you have to. Port £A0 is the status port – if bit 7 is set when the port is read, then Pluto is ready to receive a command. Writing anything at all to this port resets Pluto. Port £A1 is the data port, through which you send all the commands and data needed to produce the pretty pictures, and read data sent back by Pluto in response to your requests. It might at first seem necessary to check the status before you send each byte, but this is not so. Once the command byte has been accepted, and the status port says Pluto is ready, data can be sent as fast as a 4MHz Z80 is able to do it. This includes the use of the amazing Z80 block output instructions.