Search found 645 matches

by at67
25 Apr 2023, 17:51
Forum: Hardware and software hacking
Topic: ROM switching:
Replies: 12
Views: 4664

Re: ROM switching:

I was looking for a way to add an external reset to the Gigatron without having to change the hardware on the motherboard. This does not seem to be possible. The MCP100 has a push-pull output. It's only one trace you have to cut and then insert your circuit; even if you use the device bmwtcu pointe...
by at67
24 Apr 2023, 21:45
Forum: Hardware and software hacking
Topic: ROM switching:
Replies: 12
Views: 4664

Re: ROM switching:

Here is some more information on the original design that got lost in a different thread: Other vintage computers use writing to address 0x0, 0x1, 0x2, 0x3 to switch the bank ... For 32 and 64 kb, it's very simple: one or two D flip-flops that are set to 1 or 0 by writing to the address 0 or 1 (2 an...
by at67
24 Apr 2023, 21:22
Forum: Hardware and software hacking
Topic: ROM switching:
Replies: 12
Views: 4664

Re: ROM switching:

If you look at the schematic in the Gigatron manual, page 48, you'll see the MCP100 with a !RST output, then on page 49 you'll see the !RST output fed to the four 161's !MR input, (the program counter). All I did was add a de-bounced reset switch to the MCP100; when switching ROM's, (my ROM switcher...
by at67
24 Apr 2023, 14:03
Forum: Hardware and software hacking
Topic: gtBASIC
Replies: 435
Views: 101610

Re: gtBASIC

Can you point me to an explanation of this code: ' Defines the amount of contiguous RAM needed for blit stripes, (in this case 15*6 + 1), min address and search direction _blitStripeChunks_ 15, &h1FA0, &hFFFF, ascending Marcel's original sprite routine, (that I call a blit), is only capable...
by at67
23 Apr 2023, 12:29
Forum: Hardware and software hacking
Topic: Draw lines [tests]
Replies: 4
Views: 991

Re: Draw lines [tests]

Yeah, that's better, no more timing issues and definitely noticeably faster as well, also runs fine on my new version of ROMvX0.
by at67
23 Apr 2023, 12:26
Forum: Escape Meta Alt Control Shift
Topic: 1-byte NOP for vCPU
Replies: 3
Views: 1563

Re: 1-byte NOP for vCPU

Makes sense, unfortunately there is no vCPU NOP single byte instruction, you could do funky stuff with RET, PUSH or POP if you kept track of the stack/return address state, but that would probably be extremely inefficient in the long run. https://github.com/kervinck/gigatron-rom/blob/master/Docs/vCP...
by at67
23 Apr 2023, 09:17
Forum: Escape Meta Alt Control Shift
Topic: 1-byte NOP for vCPU
Replies: 3
Views: 1563

Re: 1-byte NOP for vCPU

All the one byte instructions modify vAC or the stack, I assume this is not good enough? What do you need a NOP for? 1) Alignment of data? 2) Padding of data? 3) Alignment of code so that you can stitch two unrelated code segments together? 1) and 2) are not an issue on the Gigatron, 3) there is a b...
by at67
23 Apr 2023, 00:00
Forum: Hardware and software hacking
Topic: Draw lines [tests]
Replies: 4
Views: 991

Re: Draw lines [tests]

In my emulator, timing errors are reported at the end of each sweep for both versions. Also version 2 try's to write to address 0.
by at67
18 Apr 2023, 08:22
Forum: Hardware and software hacking
Topic: gtBASIC
Replies: 435
Views: 101610

Re: gtBASIC

I have a set of unfinished blit and tiling routines for ROMvX0, that will allow for 2, 4 and 8 colour compression per tile/blit; I've also toyed with a Gigatron specific version of DXT1, (but it's too slow even in native code and doesn't offer any significant advantages for the Gigatron's RGB:2 form...
by at67
18 Apr 2023, 07:55
Forum: Escape Meta Alt Control Shift
Topic: Langton's Ant
Replies: 2
Views: 1745

Re: Langton's Ant

Very, very cool!