Curator // Destroyer

 So at the end of the previous update one of the ROM sockets was modified to accept a 27c128 (instead of using two 27C64 as is standard) of course I didn't have any 27c128 so I ended up using a 27C256 32KB EPROM with the image of the operating system copied twice over (N.B this wasn't actually needed. I could've just burned it into the upper half). In my search for the stock ROM however I found this site . An archive of various ZX Spectrum ROMs from various countries and different machines. So for reasons I will disclose in the future I have a bundle of 27C512s lying around, this got me thinking. There's a few different ROMS that caught my eyes when I was browsing so what if I could swap between them without having to go through the process of removing and replacing the EPROM. Now of course I could just put a dip switch on the extra address lines and be done with it but that might lead to crashes and instability if say, I flipped the switches whilst the computer was ru...

So what is a Lenigrad? Well seeing as you found this post I presume you might already know, but for those of you who don't, the Leningrad-1 (Ленинград-1) (A.k.a Leningrad48, Zonov Variant) was one of the most popular clones of the ZX Spectrum in the former soviet union. It was designed by Sergei Zonov in 1988 and of course does not use ULA but instead uses integrated circuits of the к555 family (equivalent to 74LS) with a к561ие10 (MC14520) thrown in for good luck. It's a fairly elegant design (if you're into that sort of thing) as it does so much with so little. The best schematic ive found is located here ( tranlated ) or here ( translated ). Of course it has its own caveats and compromises (perfect is the enemy of good after all) but we will get to them in time.  So as I mentioned in the previous post, I began this project and abandoned it a few years ago, only having rebegun it recently. The state I left it in was as such: I put hours into soldering it and made a cu...