Commordore 64 character color cycling (Ethan Dicks)

On Tue, Jan 31, 2012 at 1:59 PM, Kevin Reynolds <tpresence at hotmail.com> wrote: Bummer. ISTR my C-64s have socketed PLAs, but perhaps they are older units. That is more-or-less true, but the devil is in the details. In the case of the color SRAM, both the 6510 and the VIC chip access it, on alternate phases of the clock, so with a clock speed of approx 1MHz, the SRAM can be accessed twice in 1ms. That suggests that a 450ns chip is fast enough, though I might want something faster myself so that I knew it wouldn't be a problem. A 450ns chip is plenty fast enough for most 1970s and 1980s microcomputers with a single-access 1Mhz design (some of the early SRAMs like the 5101/2101/1822 256x4 SRAM had access times of 650ms... those can have problems in some places, but you won't find those in common usage after 1978 or so. They were displaced by various 4Kbit parts). Yes. It's an 82S100 that is programmed to "do the right thing" in a C-64. Yes, it fails often, but fortunately, it's a well-understood chip and can be reproduced. In the medium-term, you might be able to find someone who can burn your blank for you. Let me echo Tony Duell's recommendation of turned-pin (machined-pin) sockets. I use them exclusively, even in kits I buy (I throw the supplied cheap sockets in a box and use my own). -ethan