Search found 62 matches

by keli
Thu Jan 04, 2018 9:04 pm
Forum: ST 16MHz V2.X SERIES BOOSTERS
Topic: V2.5 BOOSTER CURRENT PROTOTYPE STATUS
Replies: 175
Views: 16084

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

How are you handling the two vs three pin bus arbitration protocol translation? Is it handled by the pld or do you simply ignore the /BGACK pin?
by keli
Tue Jan 02, 2018 6:32 am
Forum: EVERYTHING ELSE
Topic: VHDL CACHE ?
Replies: 21
Views: 2264

Re: VHDL CACHE ?

I don't think you'll need a valid bit for every byte of cached memory. You could for instance have larger cache lines. That would impose a bigger delay on initial cache misses but then more would have been fetched on subsequent reads.
by keli
Fri Dec 29, 2017 8:55 am
Forum: EVERYTHING ELSE
Topic: VHDL CACHE ?
Replies: 21
Views: 2264

Re: VHDL CACHE ?

I was reading up on some cache stuff and read similar. Something about instructions been treated as data and it screwing up the self-mod-code. You're describing the situation with internal caches where the instruction and data caches are separate. With an external cache the CPU only sees a faster R...
by keli
Thu Dec 28, 2017 11:20 pm
Forum: EVERYTHING ELSE
Topic: VHDL CACHE ?
Replies: 21
Views: 2264

Re: VHDL CACHE ?

Wouldn't adding cache mean auto modifying code wouldn't work anymore ? probably yes. But every hardware mod done is going to break something, its the price of speed unfortunately. As in this case when the cache is external to the CPU it should be fully transparent and self modifying code should wor...
by keli
Fri Dec 22, 2017 10:51 am
Forum: SOFTWARE PROGRAMMING & DISCUSSION
Topic: HDD drivers. How does it work?
Replies: 14
Views: 1044

Re: HDD drivers. How does it work?

Cache must be not set off in all cases. It is just simple measure to be sure. Problem appears when DMA writes in RAM area what is cached - and cache size is 16 KB on MSTE. Cache is not aware about it, because that write came not from CPU - while cache control is tied only to CPU. So, there will be ...
by keli
Thu Dec 21, 2017 5:00 pm
Forum: HARDWARE DISCUSSIONS
Topic: MNT VA2000 graphics card in a Mega ST
Replies: 11
Views: 1519

Re: MNT VA2000 graphics card in a Mega ST

Hi Kell. Very interesting stuff. As you might know (or not), me and Juliusz have a 68020 board for STE/MSTE with an expansion bus. I was planing on making a video card for it but looking at what you're doing may be we wont and instead support you :) Of course our bus is 32 bits but totally supports...
by keli
Thu Dec 21, 2017 4:01 pm
Forum: HARDWARE DISCUSSIONS
Topic: MNT VA2000 graphics card in a Mega ST
Replies: 11
Views: 1519

Re: MNT VA2000 graphics card in a Mega ST

/DTACK with the clock domain crossing can be more complicated than it seems.. The problem with /DTACK with a lot of the Atari chips is that it can arrive at any time, but, it generally arrives a fraction too early before the data is actually ready to read. Yes all that /DTACK is imo a design flaw w...
by keli
Thu Dec 21, 2017 2:51 pm
Forum: HARDWARE DISCUSSIONS
Topic: MNT VA2000 graphics card in a Mega ST
Replies: 11
Views: 1519

Re: MNT VA2000 graphics card in a Mega ST

Update as of 12/21/2017: I started a new HDL project from scratch instead of trying to understand all of the original VA2000 sources, as almost all of the logic was in the top file... most of it in a huge state machine. Instead I've divided everything into small modules talking to each other using t...
by keli
Thu Dec 07, 2017 3:53 pm
Forum: HARDWARE DISCUSSIONS
Topic: MNT VA2000 graphics card in a Mega ST
Replies: 11
Views: 1519

Re: MNT VA2000 graphics card in a Mega ST

A small status update. I managed to solder the sockets on to the adapter board and have done some testing. First the bad news: The bidirectional voltage converters/buffers on the VA2000 all have their /OE pins hardwired to ground. This means that while the FPGA is powering up, its outputs have an un...
by keli
Wed Nov 29, 2017 6:25 pm
Forum: HARDWARE DISCUSSIONS
Topic: MNT VA2000 graphics card in a Mega ST
Replies: 11
Views: 1519

Re: MNT VA2000 graphics card in a Mega ST

I just received the PCB for my adapter. I used ALLPCB and ordered 5 copies for USD 16.00. (Actually received 7) I have all the components, so as soon as I have a few spare clock cycles, I will have to start soldering. pcb 1.jpg I used the footprint for a straight DIN connector for the MegaBus, but a...