CURRENT PROTOTYPE STATUS (SEC 64MHz 68000)

Information and news about the 68SEC000 64MHz booster.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by exxos »

So this turned out far more annoying than I had originally anticipated :roll:

I have now redesigned the whole VPA,VMA,E based system and greatly simplified it. So now there is actually no "E-clock" as such, and the whole code generating the 40/60 clock is now gone.

Code: Select all

Z3.CK = CLK16;
Z3.D = E & !VMA5 & !VPA & !CPU_AS; 

VMA1.CK = CLK8; 
VMA2.CK = CLK8;  
VMA3.CK = CLK8; 
VMA4.CK = CLK8; 
VMA5.CK = CLK8; 

VMA1.D =  VPA # CPU_AS;
VMA2.D = VMA1 # VPA # CPU_AS;
VMA3.D = VMA2 # VPA # CPU_AS; 
VMA4.D = VMA3 # VPA # CPU_AS;
VMA5.D = VMA4 # VPA # CPU_AS;

!E = CPU_AS # VPA # VMA2;

VMA = VPA; 
Basically what happens is when VPA goes low for a ACIA cycle, VMA is also set low without any delay. What I can tell is VMA basically equates to the 6850CS which is output from GLUE which drives the 6850 CS line. There isn't really any need what I can see to add any delays on this. So when VPA goes low the ACIA CS line also goes low and enables the ACIA.

Now because of the setup time of the ACIA we need to wait around 500ns in total. So what I do is I wait 2 x clk8 cycles and then issue "E", is basically easier to understand as a output enable of the ACIA (but a bit more complicated than that).

So we select the ACIA by setting the CS low, two clocks later set Enable high which then outputs data onto the bus. But there is a setup time here also for the data to actually be valid. So I wait another 3 clock cycles and then issue DTACK via Z3.

So far this seems to be running very well for the past hour. Initially I did not have any delays on the "E" signal, and I had some intermittent crashes. The likely the ACIA may have a slight bus conflict with data on the bus from something else. So I just avoid this by delaying "E" couple of clock cycles. "E" and DTACK (Z3) are deselected when either CPU_AS or VPA goes high which terminates the cycle.

So from this there is no actual 40/60 E-clock anymore, simply used as "E" as a enable line only for the ACIA. Which is what actually the E-clock is for, but we do not need to constantly run this signal at 500KHz, its only asserted when we need it. So this greatly simplifies the code and how it all works.

Technically now the ACIA are running at a higher speed even if the CPU is running at a stock 8 MHz. I do not think this will be a problem compatible wise. The only side effect I know of this is where a sampled sound is playing and when you move the mouse the sound slows down. The effect will actually be less as the ACIA are running at a higher speed. So I do not see this as a problem.

So now I have the ACIA running from the system clock, I can now get back to overclocking the CPU over 50Mhz 8-)
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by exxos »

55MHz!!! :twisted: :twisted: :twisted: :twisted:

55mhz.jpg
55mhz.jpg (120.15 KiB) Viewed 4624 times
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
Atarian Computing
Posts: 444
Joined: Tue Aug 22, 2017 4:27 am

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by Atarian Computing »

exxos wrote: Fri Jun 01, 2018 6:59 pm 55MHz!!! :twisted: :twisted: :twisted: :twisted:


55mhz.jpg
Dude, awesome. Remember this day.
troed
Moderator
Moderator
Posts: 908
Joined: Mon Aug 21, 2017 10:27 pm

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by troed »

Amazing. How hot does the CPU get?

(Thinking about how I had to put a heatsink on the Shifter when I run it at 64MHz)
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by exxos »

troed wrote: Fri Jun 01, 2018 7:06 pm Amazing. How hot does the CPU get?
Ambient is about 27c, CPU 36c.
Atarian Computing wrote: Fri Jun 01, 2018 7:05 pm Dude, awesome. Remember this day.
:thumbup:
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by exxos »

58MHz!!! :twisted: :twisted: :twisted:

int-div from 566%(55mhz) to just shy of 600%!

.. and that's ya lot!

CPU doesn't seem to try to boot after 58MHz.. So think its safe to say that 68000 is maxed out now.. 8-) ... only took 5 years! :lol: :roll:

58mhz.jpg
58mhz.jpg (115.71 KiB) Viewed 4611 times
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
rpineau
Posts: 534
Joined: Thu Aug 17, 2017 6:08 pm
Location: USA
Contact:

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by rpineau »

:bravo:
Working ones : MegaSTE (68020) / TT030 / Falcon with AB040 & Eclipse / 1040STF
Need testing : Falcon with CT2
Atarian Computing
Posts: 444
Joined: Tue Aug 22, 2017 4:27 am

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by Atarian Computing »

:dizzy: I feel weak. This is great.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by exxos »

Just for comparisons with 16MHz CPU... This is 50MHz CPU only...


16MHz CPU

16CPU_result.png
16CPU_result.png (4.4 KiB) Viewed 4899 times

50MHz CPU
50MHZCPU_result.png
50MHZCPU_result.png (4.38 KiB) Viewed 4899 times

So we can see running the CPU faster clearly has a point of diminishing returns somewhere..

For example at 16MHz the first test is 123%, but at 50MHz is only 137%.. So a measly increase of 14% despite huge MHz increase. Though this really is to be expected anyway.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: V2.5 BOOSTER CURRENT PROTOTYPE STATUS

Post by exxos »

Been thinking about the next step.. ROM.. Though I think its time to investigate flash-rom and get that working along with fast-ram.

The flash I am looking at using is SST39LF802C-55 , still 55ns, but as I suggested before, copying to fast-ram is only way to go faster..

If anyone can find something like 10ns sram 16 bit 5V or 3.3V (higher Mb the better as limited on space) then let me know..
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
Post Reply

Return to “SEC 64MHZ BOOSTER”