Just got a crazy idea 'bulb'

General discussions or ideas about hardware.
Petari
Posts: 527
Joined: Tue Nov 28, 2017 1:32 pm

Just got a crazy idea 'bulb'

Post by Petari » Tue May 29, 2018 2:03 pm

I was thinking about how I have just like in my Ataris in last time (hmm, last 25 years by some) in my PCs multiple OS version choice. It is selectable, of course in different way than with some TOS switch - via boot manager . So, I have available: Windows XP (capturing with old card works only on it), Windows 7, 8.1 and Linux Ubuntu .
And while I looked about available Flash EPROM chips I seen that there could be something common in old Ataris and modern PCs:
All newer motherboards have 8-pin serial Flash EPROM chips, with BIOS as content. And such chips are now easier to get, cheaper, than parallel EPROMs.
And they could be of use with following scheme: 2x 1 Mbit, parallel Flash EPROMs (29F001 or like) for work - where fits 1 TOS version, but it can be bigger, of course. And 1 serial Flash EPROM with larger capacity - like 8 or more Mbits. It contains diverse TOS versions. From which 1 will be copied into smaller, parallel Falsh EPROM, and then it will be active TOS.
What is really interesting part is how to perform that copy, and how to select which TOS version to copy.
I think that it can be done purely in SW, only need little extra logic for accessing serial EPROM and serial-parallel conversion.
But maybe is smarter to do it with CPLD .
At the end, it would not cost more than some larger EPROMs, and may be easier to change TOS versions in serial EPROM. But how to put there some new content ? That could be done without programmer device, on Atari self - after DL, assembling of TOS images and copying to Atari disk.
Just for info, I solved in circuit programming of Flash EPROMs long time ago. http://atari.8bitchip.info/flashest.php
Little problem now and later may be availability of parallel Flash EPROMs. especially DIL package versions.
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

Atarian Computing
Posts: 248
Joined: Tue Aug 22, 2017 4:27 am

Re: Just got a crazy idea 'bulb'

Post by Atarian Computing » Tue May 29, 2018 4:04 pm

Well that's just a crazy good idea! I like the way you think!

atari030
Posts: 50
Joined: Mon Feb 12, 2018 12:43 pm

Re: Just got a crazy idea 'bulb'

Post by atari030 » Wed May 30, 2018 10:37 am

Silly crazy, but I like it. How about a cartridge with user selectable OS' on boot?

Petari
Posts: 527
Joined: Tue Nov 28, 2017 1:32 pm

Re: Just got a crazy idea 'bulb'

Post by Petari » Wed May 30, 2018 11:35 am

That's actually good idea. And I was thinking about SRAM instead Flash EPROM for active TOS - it writes 1000x faster, and can get probably easier.
Well, there are really diverse opportunities. Much depends from availability and prices.
Cartridge could be easiest way of usage, but it is possible to update internal serial EPROM too without removing it from machine.
In any case, you can not use cartridge self for active TOS ROM - because it's only 128 KB. Yes, I know, bank switching ... But that would need very massive reworking of TOS, and will be slower.
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

Atarian Computing
Posts: 248
Joined: Tue Aug 22, 2017 4:27 am

Re: Just got a crazy idea 'bulb'

Post by Atarian Computing » Wed May 30, 2018 2:54 pm

I know of bank switching on ROM port using both ACIA chips' RTS to do part of the switching. But that sounds like meh. What's another way of doing it? Some circuitry on the cart along with a TSR from Auto folder?

Petari
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Joined: Tue Nov 28, 2017 1:32 pm

Re: Just got a crazy idea 'bulb'

Post by Petari » Wed May 30, 2018 4:21 pm

It's not so important how bank switching is done in electronic circuit of cartridge. Can be done relative simple. Problem is on SW side of TOS - like - it performs some AES function, what is placed in upper half of TOS, so bank 1 is active. Then it needs to perform some trap call - which code is in bank 0 - so it must switch to it. That needs some extra steps, and whether using RAM for switch self, or have same code in both banks at same address - both solutions are with extra code, more steps, so slower. And that should be on plenty of locations in TOS. It is possible, but I don't think that is worth of effort. And needs still parallel EPROMs, which should be replaced with serial one - at least in this thread :lol:
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

atari030
Posts: 50
Joined: Mon Feb 12, 2018 12:43 pm

Re: Just got a crazy idea 'bulb'

Post by atari030 » Thu May 31, 2018 9:54 am

Either way the ROM's would need to be parallel? What about an SRAM buffer? Yeah, I know, nuts.

Petari
Posts: 527
Joined: Tue Nov 28, 2017 1:32 pm

Re: Just got a crazy idea 'bulb'

Post by Petari » Thu May 31, 2018 10:15 am

atari030 wrote:
Thu May 31, 2018 9:54 am
Either way the ROM's would need to be parallel? What about an SRAM buffer? Yeah, I know, nuts.
That's not nut. What I wrote about using SRAM is it, actually - some kind of buffer. The real question is how to transfer content of EPROM containing TOS images, and serial EPROM (Flash) is what is cheapest and now best available. 256 KB SRAM costs really not much. And it is possible to even put packed TOS then in initial EPROM ... There must be some other, small ROM - 16-bit one, if it works on 68000 of STE, with code for that transfer. Or probably smarter - with CPLD ...
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

tzok
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Joined: Sat Dec 30, 2017 2:27 pm

Re: Just got a crazy idea 'bulb'

Post by tzok » Fri Jul 13, 2018 12:47 pm

So you'd need to have two 1Mbit SRAM chips, an MCU and the I2C Flash. The MCU would load an TOS image from Flash to SRAM during the reset phase (it should control the reset line to be able to keep it active until copying is done). You may use 2Mbit SRAM and a bank switching, but after some thinking it is not required. Accessing SRAM by MCU should only occur when the MC68000 is in a RESET state.

Petari
Posts: 527
Joined: Tue Nov 28, 2017 1:32 pm

Re: Just got a crazy idea 'bulb'

Post by Petari » Fri Jul 13, 2018 2:07 pm

tzok wrote:
Fri Jul 13, 2018 12:47 pm
So you'd need to have two 1Mbit SRAM chips, an MCU and the I2C Flash. ....
There are 16-bit SRAM chips available too. And since it will be handled as ROM - read only, no problem that can not access low and high byte separately.
MCU and I2C Flash ? Those are some concrete parts/solutions, I guess. That's not how I design things. Task of copying serial EEPROM to SRAM is basically trivial. Can solve with 1-2 GALs + counter, for sure. But I guess that is better with CPLD .
Selection of active TOS must be done when copy starts. And that must be not triggered by reset - actually that's bad Idea. Only cold reset is what would be good. But you can not detect it, because that depends on system variables. There is SW what survives warm reset, but will not survive TOS v. change.
Better is to perform copy at power on, or with special button, combined with selector.
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

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