Tiny BASIC? Perhaps not.

[Chris Savage]

That's great - sounds like you recovered a huge treasure, there. I don't even remember where any of my old code is stored, now.

The only thing I am stumped about is that, when I read the contents of the cloned EPROM, the text you can see in my screenshot says, "COPYRIGHT 1994", however, that board is from 1991, so I'm not sure how or why that year ended up being 1994. That board was gone by then. I mean, whatever, I'm stoked to have the code back, but as I was rereading it, I realized that it wasn't possible.

[Chris Savage]

&H8400 seems pretty high in memory to start a BASIC, or any program. I also do not recognize this code, not even to where I could guess the CPU. Do you have any more info on this? Are you a member of BSKY, where you could ask them for more info (I'm too lazy to sign up right now.)

I was re-reading this thread and though to myself, when I get back to my 6502 retro computer, I think I am going to relocate BASIC at $8400 just for you! LOL

[granz]

I was re-reading this thread and though to myself, when I get back to my 6502 retro computer, I think I am going to relocate BASIC at $8400 just for you! LOL

Ha, that's good. Although with the 6502 having it's start location in upper memory space, that would have you with a system (most conveniently for the design) with 32K ROM in the entire upper half of memory. I do remember seeing where half of the memory is ROM (many of the 1802-based computers did that,) but that isn't exactly max-RAM friendly.

[Chris Savage]

I do remember seeing where half of the memory is ROM (many of the 1802-based computers did that,) but that isn't exactly max-RAM friendly.

Most of my original 6502-based designs were a 32K SRAM from $0000-$7FFF and a 32K EPROM from $8000-$FFFF. In these cases, the memory-mapped I/O shared space with the RAM, which was weird, but I ignored it. My stack occupied 256 bytes at the end of RAM. I used to use labels, like RAMHIGH, RAMLOW, ROMHIGH and ROMLOW as constants to define the boundaries.

Later, I had an application that required 48K RAM, so I split the memory space into 8K blocks with 48K RAM and 16K ROM. I used a 74LS138 to select each 8K block of memory. At some point I started using Dallas NVRAM modules, like the DS1225.

My Z80 designs were exactly the opposite. ROM from $0000-7FFF and RAM from $8000-$FFFF. This made address decoding simple. You'd literally just run the A15 line from the CPU through a single inverter, and directly to the ROM chip /CS. The inverted signal to the RAM /CS. The A15 line selected whether you're in ROM or RAM space. Fun times!