> So how come the Spectrum manages to refresh 128K of memory without all this > hassle then?
Don't ask me.. but it *does* use different chips... 8x16k if I remember rightly... It *may* be something to do with the DRAMS Bruce was using... > > 2) So that it can show the screen with as little video contention as > > possible.. > > But it isn't showing the screen so why does that matter? > > Incidentally it is very irksome that whoever designed the Sam did not > think to put even a small amount of non-contended RAM in for critical > routines. For example, the memory in the 512K machine is physically > located in at least two places and the display can only be taken from > one of them at a time, so why isn't the other bank (whichever one does > not contain the display) non-contended? Simple -- it would require a sum total of about... ooh let me think... approximately 16-18 more pins for access to the memory by the ASIC... Now if *you* want to tell me how to get that many more without increasing the footprint and the cost of the chip, then please do... remember as well that a chip that size would require twice as much development funding (approx) because VLSI insist on rigorously checking and rechecking before it goes to silicon. Anyway, if you can do a better job, please do :) Not that I hold what Bruce did in high regard or anything ;) The only reason the SAM doesn't have more colours in its palette is because of lack of pins. The same with most things you can think of that are missing on it -- Bruce ran out of pins on the ASIC and had to cut stuff out. Apparently there is plans for an ASIC with hardware scrolling etc -- Bruce talked to Rob Holman about it in the early days... it didn't materialise because Bruce was under intense pressure from the directors, and thus he had to cut a lot out.. Actually, Bruce resigned from the board of directors (as did Alan), but they were brought back (my facts may not be correct here -- at least one of them did resign)... The reason MGT died was because of (1) New Computer Express (2) Mistimed product in an age when the Consoles were getting big and (3) The directors decided to move buildings when they couldn't afford to and there was *NO NEED* to expand. The building they moved to is *still* vacant today, with the MGT and SAM posters up. So... that's why the SAM is the state it is... Moral for the day: Don't float your company if you can help it -- you get put under too much pressure and can't do thing to your own standards -- you get rushed... Si
