UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Mark1960 · 12th Nov 2020, 2:23 am

Its difficult to decide how far to go in extending the MK14.

I though putting the RAM and EPROM on an extension board would leave it open for me to revert to the standard MK14 if I do ever source a spare set of PROMs.

Another option is to have only RAM, but battery backup and some method of loading the RAM, maybe using an ft245 similar to a previous z80 project.

Adding memory could also include a latch for the high nibble, but then I don’t think there is an easy way to enable the onboard IO and memory only in the bottom 4K, and putting holes for the onboard IO in every 4K page would make it difficult to run NIBL which would be the main purpose of adding so much extra memory. It seems to me than an extension to the MK14 should stick to the 4K limit with a separate project to use NIBL.

12th Nov 2020, 2:23 am	#891
Mark1960 Octode Join Date: Mar 2020 Location: Kitchener, Ontario, Canada Posts: 1,294	Re: Mk14 vdu Its difficult to decide how far to go in extending the MK14. I though putting the RAM and EPROM on an extension board would leave it open for me to revert to the standard MK14 if I do ever source a spare set of PROMs. Another option is to have only RAM, but battery backup and some method of loading the RAM, maybe using an ft245 similar to a previous z80 project. Adding memory could also include a latch for the high nibble, but then I don’t think there is an easy way to enable the onboard IO and memory only in the bottom 4K, and putting holes for the onboard IO in every 4K page would make it difficult to run NIBL which would be the main purpose of adding so much extra memory. It seems to me than an extension to the MK14 should stick to the 4K limit with a separate project to use NIBL.