When is a ST not a ST anymore ?

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Stimpy
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Re: When is a ST not a ST anymore ?

Post by Stimpy » Sat Apr 07, 2018 9:33 pm

exxos wrote:
Fri Apr 06, 2018 11:04 pm
dhedberg wrote:
Fri Apr 06, 2018 11:02 pm
Does anyone know how compatible the Suska is? Does anyone here own one, or know anyone who owns one?
I never heard of anyone owning one.. The chips are supposed to be 100% compatible.. but only way to know, is to build them one by one and throw everything under the sun at it...
I provided quite a bit of feedback to the suska project as (I think) I implemented the separate cores into one FPGA before they did, probably worlds first. I didn't implement the CPU as I don't think it was complete and the memory was SRAM rather than DRAM. TOS was in an bit ROM double clocked to get 16bits out. The video output actually used a Video DAC from a falcon! This was all about 10 years ago.

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Re: When is a ST not a ST anymore ?

Post by exxos » Sun Apr 08, 2018 1:54 am

Maybe you can help us with adapting the code for the projects we have in mind ?
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Darklord
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Re: When is a ST not a ST anymore ?

Post by Darklord » Sun Apr 08, 2018 11:12 pm

Very interesting thread....

Way back when I first re-cased my Falcon into a Wizztronics case, I had several people
declare that it was no longer a Falcon. /shrugs.

I also had some people say that as long as it was originally manufactured by Atari, then
it was still an Atari. Accept no substitutes apparently. :)

I don't care for emulators, a well known fact. I'm not also a big fan of the MiST and
hardware like that.

I like Chris's idea about redoing a 1040. I'd happily call it an ST, just not an *original* ST.

Hope that makes sense.
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Re: When is a ST not a ST anymore ?

Post by exxos » Mon Apr 09, 2018 1:27 pm

Darklord wrote:
Sun Apr 08, 2018 11:12 pm
I don't care for emulators, a well known fact. I'm not also a big fan of the MiST and
hardware like that.

I like Chris's idea about redoing a 1040. I'd happily call it an ST, just not an *original* ST.

Hope that makes sense.
For me the main thing is compatibility. Basically the Falcon is a upgraded ST, obviously it is not a ST. My overall aim is to keep the ST design is close to original as possible but update the chips so we can use faster memory and CPU etc. while the chips are emulated, it is emulating the original ST architecture, so my view it is still a ST.

It can be debatable about using different silicon technology do the job some people could argue its not original anymore, which it basically isn't. But if the chips are 100% compatible then there should not really be any reason not to call it a real ST.

It is basically the same as a power supplies in the STF/E. There are several different brands of power supply or basically doing the same job. Which one is a original ST ? Of course they all are, but they all use different power supplies and slightly different technology in them.

What I see is exactly the same in replacing the MMU for example, is still hopefully does exactly the same job, slightly different technology just like the power supplies. Of course we could go deeper into brands of chips.. We can just look at the CPU, MOT or ST brands etc.

Some people prefer not to buy my power supplies as they are not original. I can perfectly understand that. The thing is, my power supplies are just another brand like the other several brands already use. The only thing is my power supplies did not come out when the machine was produced it is a replacement part and obviously not original as the ST never had my power supplies fitted from factory.

I think everyone has their own take on which is original and not. Of course however they came out of the factory is its original form. But this does not mean the parts inside the identical across the whole production runs of the machines. So if we took a factory SR98 and replaced it with a DVE power supply, is that machine still original or not.. It is different as is not how it came out of the factory, of course the different power supply also came out of the factory which is a original part, but not original to that machine.
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Stimpy
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Re: When is a ST not a ST anymore ?

Post by Stimpy » Tue Apr 10, 2018 1:11 pm

exxos wrote:
Sun Apr 08, 2018 1:54 am
Maybe you can help us with adapting the code for the projects we have in mind ?
It would come down to spare time of which I have virtually none, but perhaps enough to help advise or point any potential pitfalls out?

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Re: When is a ST not a ST anymore ?

Post by Darklord » Fri Apr 27, 2018 12:40 am

I fully agree about compatibility. Keep up the great work Chris! :)
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tzok
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Re: When is a ST not a ST anymore ?

Post by tzok » Fri Jul 13, 2018 1:07 pm

What is the difference between emulating a whole computer in one FPGA chip and emulating most of the crucial chips in a separate FPGAs... for me it is still only an emulation. So cycle accurate copies of original chips in form of ASICs is ok, FPGA emulation is only emulation.

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Re: When is a ST not a ST anymore ?

Post by Petari » Fri Jul 13, 2018 2:23 pm

Calling some FPGA solution emulator is not exactly correct. Indeed, some parts are emulation - mostly screen, because it has output to modern displays, so not PAL/NTSC freq. But CPU is not emulated. That's even bad to hear. If you'd emulate 68000 like it is emulated by SW on PC, you would need min 10x more CPU power than for what is the case: cloning, reverse engineering of it. Cycle accuracy problems are normal with reverse engineering. Motorola self did not keep it with slightly changed 68010. Why 68000-s manufactured by others, like ST (SGS Thompson) were cycle accurate ? Because they got complete CPU design, masks for chemical process of chip making.

I would not compare PSUs with some complex chip cloning. Later is much-much-much harder. Will anyone ever make fully 100% compatible ST is very questionable by me. Especially as there are many chip revisions.

When is it so different that is not correct to call it ST ? When something important is changed: like video output system. Or when it works with PC keyboard. Changing CPU to 68010 for instance would not mean that it is not ST anymore, despite that it will make it much less compatible than using PC keyboard with MIST. Or via Eiffel. Not simple black or white dilemma.
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Re: When is a ST not a ST anymore ?

Post by tzok » Fri Jul 13, 2018 2:51 pm

In most cases reverse engineering gives more or less incomplete emulation. FPGAs run a VHDL code, potentially it could be very close to the original design, but we'd have to have original chip production documentation to fully implement it in VHDL. For example - STf and STe had a joystick port controlled by a MCU in the keyboard, connected through a serial line with a motherboard. This lead to a specific delays, which are hard to emulate in FPGA if we don't have the full documentation of the original MCU and code it originally run, but has a great impact on the gaming experience. Some games become very hard to play just by using SCART to HDMI converter, which adds some slight delay (2-3 frames). On the other hand most emulator programmers tend to take some shortcuts and/or optimizations.

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Re: When is a ST not a ST anymore ?

Post by Petari » Sat Jul 14, 2018 8:07 am

You will never see original documentation for Atari chips, and same stays for used Motorola and other chips.
And you talk about incomplete emulation. What about incomplete and/or inaccurate reverse engineering of chips ? Because that's what we see and will see. The real problem here is that you need to invest 99% of time for only 1% of SW - and that's simply bad trade. By solving regular work - video is here most problematic part - you will make 99% of SW working properly. That 1% of SW what uses undocumented and in most cases some special side effects of concrete chips will need much more time to solve. And what is worst, it often changes from Atari model to other model, used chip versions.

Delay of IKBD chip is caused mostly by low serial transfer rate between IKBD and ACIA chip. It's about 8 KHz, so 1 byte needs about 1mS . Joystick action may need 4 bytes to transfer, so it may take little more than 4mS, what is - oh what a shock - 1/200 Sec . That's really nothing, even for fastest players.
And it can be emulated pretty well. You talk about IKBD MCU code, but that makes even less delay.
Of course, there is plenty of games with laggy controls, but that's because their code. For instance very good game Rainbow Islands is very hard in later levels right because lag on joystick, when there is lot of it on screen.

Considering SCART to HDMI - that's simply not the right way if you want max picture quality and min delay. Only right way is to put HDMI (or VGA) converter inside ST, to digital RGB line outputs from shifter (3x3 lines) and convert it to 30-31 KHz signal. And I don't think that all SCART(RGB) to HDMI have so big delay.
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