That sounds great Dave, so what help do you need from me (that I can do)? Lee - Back to the QL- ----- Original Message ----- From: Dave Park To: ql-us...@q-v-d.com Sent: Wednesday, February 23, 2011 8:07 PM Subject: Re: [Ql-Users] 57 images of dismantling a Sinclair ZX-81.
On Wed, Feb 23, 2011 at 1:11 PM, Lee Privett <lee.priv...@gmail.com> wrote: > see there is another thing, if only I had JS ROMs :( The card I'm proposing could hold a 128KByte or 256KByte PROM. By manually switching one (128K) or two (256K) Address lines, I can manipulate any 64K block of the PROM to appear at $0000. Thus, it would be perfectly possible to have a JM+TK2, JS+TK2, Minerva+TK2 image, and a spare 64K area. I could go further and allow people to submit a preference for order, toolkit, etc. If they supplied the image (which implies they owned it) I could build the image and burn the PROM to suit. I keep saying PROM because I have a box of 1000 256KByte PLCC PROMS in the workshop, so they're essentially free... I just need to check out the chip select lines on the two ROM sockets to see how they operate - someone has said that in the $8000 socket, CS asserts for the entire 32K block, but to me that suggests a conflict with the ROM port. I'll want to check it out, unless someone can definitively explain the address decoding logic from $0000 to $C000... Tony? Back on topic, I was amused by how in describing the ICs of the ZX81, the poster included the date and location codes... EG: P8233 indicates the IC was made in the Philippines in week 33 of 1982. You just need to look up each manufacturer to find out what the country/factory codes are. And the big metal thing? It's a heatsink. Dave _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
