Search found 37 matches

by lb3361
03 May 2021, 20:56
Forum: Hardware and software hacking
Topic: New vCPU instructions 2.0
Replies: 73
Views: 3870

Re: New vCPU instructions 2.0

I didn't just mean it for prefix instructions. I just observe that half of the page3 instructions waste three cycles adjusting vPC. For these instructions, vPC is adjusted twice: once in the instruction body (+/-1) and once in the dispatch code (+2). Three cycles, that's 10% of maxTick, an obvious t...
by lb3361
02 May 2021, 20:34
Forum: Hardware and software hacking
Topic: New vCPU instructions 2.0
Replies: 73
Views: 3870

Re: New vCPU instructions 2.0

Another idea you might want to entertain. Because nearly all old vcpu instructions were two bytes long, it made sense to lose 3 cycles adjusting vPC on the occasional one- or three-bytes long ones. But this is no longer the case with all your new instructions. So what about having three versions of ...
by lb3361
02 May 2021, 14:10
Forum: Hardware and software hacking
Topic: New vCPU instructions 2.0
Replies: 73
Views: 3870

Re: New vCPU instructions 2.0

Agreed.
by lb3361
02 May 2021, 11:41
Forum: Hardware and software hacking
Topic: New vCPU instructions 2.0
Replies: 73
Views: 3870

Re: New vCPU instructions 2.0

This may not be important, but an easy way to implement the two bytes Bcc is to make the current Bcc opcode a NOP. That won't work unfortunately, as you need to return a different cycle count in AC depending on which path you took.. Sorry. We misunderstood each other. The nop idea was precisely a w...
by lb3361
01 May 2021, 19:24
Forum: Hardware and software hacking
Topic: New vCPU instructions 2.0
Replies: 73
Views: 3870

Re: New vCPU instructions 2.0

Congrats. This may not be important, but an easy way to implement the two bytes Bcc is to make the current Bcc opcode a NOP. Then the next instruction is a short Bcc. The only problem is that this makes the three bytes sequence a bit slower than the old Bcc. On the other hand, it would be easy to ch...
by lb3361
01 May 2021, 13:18
Forum: Hardware and software hacking
Topic: New vCPU instructions 2.0
Replies: 73
Views: 3870

Re: New vCPU instructions 2.0

This is very cool. st(vCpuSelect,[vCpuSelect]) :-O. I suppose this one is worthy of Marcel. In fact your Jcc instructions are no longer than the "short" Bcc ones, and they might even run as fast. This leaves very few reasons to use Bcc anymore. Did you have a chance using a different maxtick for the...
by lb3361
30 Apr 2021, 11:09
Forum: Hardware and software hacking
Topic: New vCPU instructions 2.0
Replies: 73
Views: 3870

Re: New vCPU instructions 2.0

Also I just realized that the vSPH change does not only changes PUSH and POP but also sys_Exec! There may be other places like that. I just added support in my lcc for some of your instructions. Some of them are *very* useful. POKEI/DOKEI/POKEA/DOKEA save a lot of bytes. I wasn't able to implement m...
by lb3361
24 Apr 2021, 19:51
Forum: Hardware and software hacking
Topic: Possible ways of speeding up the Gigatron
Replies: 13
Views: 564

Re: Possible ways of speeding up the Gigatron

To what extent can you use this fifo approach to decouple the VGA timing from the Gigatron clock? Maybe you need two fifos for this. The gigatron fills one at its leisure, while the VGA monitor gets pixels from the other one using its own clock. Then one could speed up the gigatron clock without mes...
by lb3361
24 Apr 2021, 19:36
Forum: Hardware and software hacking
Topic: New vCPU instructions 2.0
Replies: 73
Views: 3870

Re: New vCPU instructions 2.0

About CMPHI/CMPHS not being much tested. It turns out that the complicated code to do this without cmphi/cmphs is even less reliable. See https://github.com/kervinck/gigatron-rom/issues/192 ? This deserves fixing... I was working on the c runtime and I wanted to see how this was done in tiny basic. ...
by lb3361
23 Apr 2021, 17:42
Forum: Hardware and software hacking
Topic: New vCPU instructions 2.0
Replies: 73
Views: 3870

Re: New vCPU instructions 2.0

You're the best person to make that call.