Search found 490 matches

by marcelk
17 Feb 2020, 07:11
Forum: Escape Meta Alt Control Shift
Topic: Discrete transistor computers
Replies: 2
Views: 3900

Re: Q1 Discrete transistor computer

ECL wrote: 16 Feb 2020, 19:25 from the guy who wrote the JWM window-manager
The site doesn't give an operating speed for the Q1. But it appears to use slow transistors also.
by marcelk
16 Feb 2020, 23:31
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 57866

Re: Expansion bus

If there's another master on the i2c bus, there isn't much we can do. As I understand it, we have to become responsive to its clock. That's the same problem we faced with PS/2 and that we ran away from. But given that SPI software support is still ploughing on I believe we have time to get it right....
by marcelk
16 Feb 2020, 22:00
Forum: Hardware and software hacking
Topic: associate the .gt1 filetype for web autoloading
Replies: 8
Views: 7226

Re: associate the .gt1 filetype for web autoloading

ECL wrote: 16 Feb 2020, 21:24 https://addons.thunderbird.net/en-US/th ... hunderlink

could be useful as a basis for implementing such .gt1 links
Maybe you need to explain a bit more. Is that something you have experience with applying in a similar context? Is it your project?
by marcelk
15 Feb 2020, 16:49
Forum: Escape Meta Alt Control Shift
Topic: Discrete transistor computers
Replies: 2
Views: 3900

Discrete transistor computers

Homebrew CPU wisdom dictates that discrete transistor computers must be much slower than TTL computers. "Due to capacitances and noise levels", as people usually put it. The MT15, Megaprocessor and Monster6502 are then given as examples. After all, each of those max out well below 1 MHz. However, ba...
by marcelk
15 Feb 2020, 14:22
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 57866

Re: Expansion bus

Do you mean that any i2c transfer shouldn't be operated in parallel with SPI0/1 activity? That's not an unreasonable constraint. If software can handle it, there's no need to add hardware for it. The mantra still stands. Anyway, in this schematic, SS2/3 must be kept low during SPI transfer so that M...
by marcelk
11 Feb 2020, 19:38
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 57866

Re: Expansion bus

Don't trust the output too much :-). This is still code that was supposed to work on one specific card I had at hand. And it appears to work on several, but for the wrong reason. I best address it when I can resume with the GTOS shell. I like the idea of turning 2 of the ports into a single i2c port...
by marcelk
10 Feb 2020, 22:38
Forum: Hardware and software hacking
Topic: GTOS
Replies: 4
Views: 4477

Re: GTOS

From skimming over the older CardTest code, I conclude that byte addressing isn't detected correctly. And even it if were, it wouldn't work anyway, because the way it is handled further on isn't correct. I believe this is consistent with the observations so far, including jwolfram's today. This is p...
by marcelk
10 Feb 2020, 11:24
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 96
Views: 57866

Re: Expansion bus

That's more than likely the same software issue mentioned in the GTOS thread:
viewtopic.php?p=1215#p1215
I haven't found time to dive into it yet...

[Edit: created GitHub issue: https://github.com/kervinck/gigatron-rom/issues/161]
by marcelk
08 Feb 2020, 16:45
Forum: Hardware and software hacking
Topic: Interrupts:
Replies: 11
Views: 8775

Re: Interrupts:

Consider it done and tested: vertical blank interrupts now work fine in dev.rom. They trigger at the top of vertical blank whenever frameCount overflows to 0 and the vIRQ vector is non-zero. This vector must point to vCPU code. vPC and vAC will already be saved in the top of the zero page. The "vRTI...
by marcelk
08 Feb 2020, 14:37
Forum: Hardware and software hacking
Topic: v6502 mini-assembler in Apple-1 emulator
Replies: 3
Views: 4714

Re: v6502 mini-assembler in Apple-1 emulator

The mini-assembler now has its entry point moved to $EEE because that's easier to remember than $D13. So from wozmon you enter its `!'-prompt with: EEER The I/O (keyboard, display) is now handled by PIA chip emulation instead of the v6502 BRK instruction. In the original Apple-1, all I/O goes throug...