>> Erm... No. You probably meant to say four /bits/ (a nibble). Four bytes >> is 32 bits per pixel? Not likely, on a SAM. The Kaleidoscope wasn't too >> bad, IIRC... But no programs supported it. > > Yeah, four bits, absolutely! It was late. And as for the Kaleidoscope, >didn't the Newsdisk carry a demo? Besides, as far as I recall the SAM >couldn't even scroll a page of regular graphics, what would a single >handed z80 have been able to do with the 16bit colour (or whatever it >was) of the Kaleidoscope?
The Kaleidoscope didn't increase the number of CLUT entries, or the resolution. There was still four bits per pixel, so there's no extra bitmap data to shift round. >Andrew Collier wrote: >> The Sam's 512K RAM is arranged in 32 pages of 16K each. The ROM comes in >> two 16K sections, which go in sections A and D. As far as BASIC is >> concerned, 16384 is the start of RAM page 0. > > Actually I only have a 256k SAM (it is a genuine MGT one if that counts >for anthing though), is it correct to assume that pages 14&15 start in >sections C&D? That depends what you're trying to achieve.... The ROM normally outputs 31 to LMPR, which means that section A contains ROM0, and section B contains RAM page 0 which is where the system variables and stack are held. It will move HMPR around as appropriate, to access BASIC programs, the screen or machine code routines etc. If you CALL a machine code routine from BASIC, it will normally be paged into section C (except when the routine is located in pages 0 or 2, which get called in sections B and D.) The ROM keeps the default screen in pages 14 and 15 on a 256K Sam. The DOS would load into page 13. > Also, slightly less related, what are the pros and cons of developing >in SIM Coupe? I have no method to connect my SAM to a monitor - so what >is the compatibility like as far as simple uses such as mine will be? Unless you start fiddling about with complex, demanding and exact timing issues, you're unlikely to have a problem. >> >If I page out >> >the ROM can I use the lower 32k for the screen and the higher 32k for >> >program . . . >> >> Yes indeed, though I normally do it the other way round to catch mode 1 >> interrupts. > > 'mode 1 interrupts' - is there no 50Hz interrupt in other graphics >modes? Mode 1 interrupts - I'm referring to processor interrupt mode 1, where the effect of an interrupt is to call 56 dec. This is as opposed to processor Interrupt Mode 2, which you may have already used on the Spectrum, which involves setting the I register to the high byte of a table of addresses etc etc. I don't use IM2 very often. Rest assured, the 50Hz frame interrupt occurs properly in all graphics modes. > And, on a slight aside, is it actually 50Hz now, or still about >50.8? Actually, it's 50.0801282051... or something like that. Normally there are 625 scan lines in exactly 1/25 of a second. The SAM only displays 312 scan lines per frame, so (assuming that one scan line takes the same length of time in each case) then it should take 0.019968 seconds to display one frame. Andrew -- | Andrew Collier | email [EMAIL PROTECTED] | Talk sense to a | Part 2 NatSci | http://carou.sel.cam.ac.uk/ | fool and he +----------------+----------------ICQ:38645805-+ calls you foolish | Selwyn College Student Computer Support Team | -- Euripides
