Search found 48 matches

by PurpleGirl
25 Nov 2019, 06:04
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 57
Views: 26782

Re: Modified Gigatron Design Ideas

So a 377 or 2 161's might be better for what I have in mind, though a tristate buffer might work if the data is streamed. So it depends on the application. But adding opcodes, I think I'd want an X-Out rather than a load.
by PurpleGirl
24 Nov 2019, 01:39
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 57
Views: 26782

Re: Modified Gigatron Design Ideas

Thanks. I'll read that. But I see the opcode thing as not too hard. Make X-out closer to another register. I see, so Mr is the reset, and holding the clock low causes it to act more like a register. If I were going to mod it and make it more like a register, I'd probably be more interested in a 244 ...
by PurpleGirl
23 Nov 2019, 23:06
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 57
Views: 26782

Re: Modified Gigatron Design Ideas

It seems like that could be remedied in other ways. The X-Out could be given some opcodes. The low-hanging fruit is 11 of the 12 NOPs. I could create an instruction like LD XOout, AC by piggybacking off of a NOP like I've been mentioning. So since they are not used and do nothing, it would then be a...
by PurpleGirl
23 Nov 2019, 20:24
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 57
Views: 26782

Re: Modified Gigatron Design Ideas

I don't know if I will actually do the dual Gigatrons. Expense is an issue right now. Besides, I am the type who has to see the end before starting something. I do have questions about X-Out (on the right one). It appears from the schematics that it is currently being synced by the H-sync, so what w...
by PurpleGirl
22 Nov 2019, 21:07
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 57
Views: 26782

Re: Modified Gigatron Design Ideas

I am not understanding why you are having difficulty following. I will try again. I asked if the syncs from the 2nd Gigatron in this arrangement (the one you put on the left) could be used to drive the keyboard shift register on the first one (the one you put on the right)? Thus you wouldn't need to...
by PurpleGirl
22 Nov 2019, 20:24
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 57
Views: 26782

Re: Opcode mods

Yeah, I thought the concept of CPU escape sequences would be interesting. So intercept 2 of the unused NOPs and piggyback onto them. One of them switches out some of the control circuitry to allow for opcodes to be recycled to add additional functionality. The other piggybacked NOP switches the orig...
by PurpleGirl
22 Nov 2019, 01:01
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 57
Views: 26782

Opcode mods

In the past, I mentioned a way to use a spare NOP as a way to signal an external device, such as resetting a video circuit if you don't know the state. You could make a crude decoder to NOR the pins that are supposed to be off and AND them with the ones that belong on for your instruction. The NOPs ...
by PurpleGirl
22 Nov 2019, 00:35
Forum: Hardware and software hacking
Topic: Modified Gigatron Design Ideas
Replies: 57
Views: 26782

Re: Modified Gigatron Design Ideas

Thank you! I only posted what I did in the other thread because of the relevance of having 1 Gigatron specialized for video, sound, and emulated interrupts. Actually implementing it is better discussed here. Software interrupts would still be used, just on the dedicated Gigatron. So one could have a...
by PurpleGirl
17 Nov 2019, 20:09
Forum: Escape Meta Alt Control Shift
Topic: Atari 8-bit architecture and homebrew versions
Replies: 3
Views: 1914

Re: Atari 8-bit architecture and homebrew versions

The 2600 demo was impressive. The demos for modified Atari computers and homebrew clones are even more impressive. The Eclaire is another homebrew Atari clone, but it is an FPGA implementation with a turbo Sally and other Atari chips in the FPGA, whereas the 1088 XEL uses authentic Atari chips, with...
by PurpleGirl
16 Nov 2019, 01:10
Forum: Escape Meta Alt Control Shift
Topic: Atari 8-bit architecture and homebrew versions
Replies: 3
Views: 1914

Atari 8-bit architecture and homebrew versions

When I was a teen, I owned an Atari 800 that I still have today. Recently, I've been researching the Atari 8-bit computers. It is interesting how the hobbyist and FPGA community have made all sorts of mods and are still using them or homebrew versions of them today. Atari 8-Bit Computer Architecture...