Just got a crazy idea 'bulb'

General discussions or ideas about hardware.
atari030
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Re: Just got a crazy idea 'bulb'

Post by atari030 » Sat Jul 21, 2018 9:10 am

If you are only using TOS ROM's then you won't need survive a reboot. Just remember the last ROM loaded, rinse and repeat? If I understand what you are trying to do correctly?

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exxos
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Re: Just got a crazy idea 'bulb'

Post by exxos » Sat Jul 21, 2018 9:49 am

This actually gave me a idea with new booster (is some relevance to topic I think :lol: ) .. Problem with serial flash is max speed (quick look on mouser) is 104MHz. Now my dualtos board uses 32MHz and pushes a 55ns ROM (20MHz).. So a serial ROM would be around 8 times slower than a parallel ROM , so I never considered it a good idea..

BUT...

I am considering having the booster copy ROM into 10ns SRAM.. So really slower serial ROM wouldn't be much of a problem, just initial boot up of machine may take longer.. depends on how much data needs to be sent via SPI.. assume address has to be sent, then data 16bit has to be recovered.. so copy to SRAM on boot could take some seconds..

As I have space issues on the PCB to fit all, a serial ROM sounds like a better idea now. Also no need for parallel flash at all.. TOS select would be done via settings in NVRAM like in falcon (or some small boot rom to store settings which I already worked out a while ago).

All would need is some app to program the serial flash in GEM ;) ;)
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Petari
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Re: Just got a crazy idea 'bulb'

Post by Petari » Sat Jul 21, 2018 11:44 am

Of course serial EEPROM is not usable at all instead parallel ROM or RAM in some computer. It is good only for non-volatile data storage - of not much data. Main reason is not clock rate, how fast can read some value, but that it is not random access but serial.
If you use clock of only 8 MHz, and have serial-parallel conversion in HW, then can achieve nearly 1 MByte/sec transfer from serial to parallel RAM (assuming that it works with 1 bit/clock cycle, otherwise can use higher clock) . That means no delay practically. If CPU need to to all - so serial parallel conversion, then it could be something like: reading 1 bit - 1 , SW shift - some 2 > about 3 microsecs for only 1 bit (calculating with 8 MHz clock) , what means about 45 KBytes/sec - so about 5-6 secs for 256 KB .
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SolderGirl
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Re: Just got a crazy idea 'bulb'

Post by SolderGirl » Tue Aug 07, 2018 5:19 pm

I had a similar idea a while ago, but my idea was a bit diffrent.
My plan was to use flash eprom to store the OS, and a MCU for programming them.
Using flash gets around the issue of writing new os on each boot.
The only thing needed to change the OS would be a special piece of software to write to the MCU.
I think there are some free GPIO pins, like the one on the display connector, maybe more.
If there is only one GPIO, it could be used as a trigger, and then send data to MCU via 2 pins
of the parallel port via bit-banged I2C.

Of course this would need a piece of software that takes over the system completely,
so there is no access to the ROM while writing to the MCU.

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Re: Just got a crazy idea 'bulb'

Post by Petari » Tue Aug 07, 2018 6:33 pm

SolderGirl wrote:
Tue Aug 07, 2018 5:19 pm
I had a similar idea a while ago, but my idea was a bit diffrent.
My plan was to use flash eprom to store the OS, and a MCU for programming them.
Using flash gets around the issue of writing new os on each boot.
The only thing needed to change the OS would be a special piece of software to write to the MCU.
I think there are some free GPIO pins, like the one on the display connector, maybe more.
If there is only one GPIO, it could be used as a trigger, and then send data to MCU via 2 pins
of the parallel port via bit-banged I2C.

Of course this would need a piece of software that takes over the system completely,
so there is no access to the ROM while writing to the MCU.
Not exactly clear what type of Flash you meant. MCU, CPLD, or some GALs - not really relevant. It can be solved in many ways. Surely need to stop 68000 before TOS is written to RAM. Or to use separated. small capacity ROM for initial copy from serial Flash to RAM. Then switch to it as OS ROM.
Whole idea came just because parallel Flash EPROMs becoming expensive and harder to find.

I solved in circuit programming for parallel Flash years ago: http://atari.8bitchip.info/flashest.php
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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Re: Just got a crazy idea 'bulb'

Post by SolderGirl » Tue Aug 07, 2018 7:20 pm

Well, if the main idea was to get rid of parallel flash chips, then my idea is totally useless in this case.

How about using a battery or super-cap to keep the SRAM contents, so there is no need to re-program the TOS on every boot?

Petari
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Re: Just got a crazy idea 'bulb'

Post by Petari » Tue Aug 07, 2018 7:50 pm

That's good idea in fact. And actually, you need to reprogram not at every boot, but every power on only. OK, you probably meant that.
Only that first time it needs somehow to get proper content :D And in case of some data corruption.
Indeed, transfer from serial to SRAM is what is hardest part here.
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.

SolderGirl
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Re: Just got a crazy idea 'bulb'

Post by SolderGirl » Tue Aug 07, 2018 9:00 pm

I think the transfer from serial eprom to sram can be done relatively easy with a PIC MCU and a binary counter for the adress.
Those PIC's have SPI/I2C in hardware, and lots of IO pins. And they are dirt cheap and easy to program in C.
Maybe there are others that are also easy to use, but i personally have most expirience with PIC.
It can read from serial eprom, just count the adress (no random access needed) and write 16 bit at a time to the ram chip.
Just very little code is needed for the PIC, and it has some more functions that might be useful.
For example, most PIC's also have 256 or 1024 Bytes of internal eprom, that can store config values.

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Re: Just got a crazy idea 'bulb'

Post by Petari » Wed Aug 08, 2018 9:14 am

Yeah, PIC should do it well. I have no experience with programming it, and I hate C :D In last time did not see much mentioning of PIC, so almost forgot about it.
I think that transfer from serial to SRAM should happen during reset pulse active. If it is not enough long then can make longer. But 256KB should transfer in less than half sec. What depends from how fast can PIC read serial data. Even 2 secs is not bad - so much can every user survive :D
Selecting active TOS v. is what could be solved with same PIC, I guess. For instance with 4 small buttons and 4 LEDs - which indicate active one. I did it on my Spectrum long time ago, and is much nicer than some switches.
Well, looking your posts and WEBsite, I'm sure you can do it. I'm now focused mostly on content of serial EEPROM - and that needs really lot of time and testings.
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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