Author Topic: The Missing 84+ Extra RAM Pages (hardware change)  (Read 54608 times)

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Offline Billeekid

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Re: The Missing 84+ Extra RAM Pages (hardware change)
« Reply #120 on: September 21, 2011, 06:27:30 pm »
"beloved crystal" what would that mean? I have RC cars in mind,lol.
   So the calculators are 16 bit, I'm assuming that is necessary for more advanced calculations and memory sizes? I'm still studying the 8-bit principle  :P  but I'm failing to understand what issues arise with reprogramming the flash memory. I've always been told that my flash drive will eventually go corrupt from use, but after the flash memory is reprogrammed, won't the remaining memory function as RAM with out any future corruption?  Can you partition the flash memory!?   Well, now I'm gonna have to find this bespoke "low memory" GB emulator, I am a little bit excited to play Links's Awakening.  :)

Offline Runer112

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Re: The Missing 84+ Extra RAM Pages (hardware change)
« Reply #121 on: September 21, 2011, 06:40:19 pm »
Technically the calculators have an 8-bit processor, as they have an instruction word size of 8 bits and the general use registers are each 8 bits. But that's not really important.

Regarding reprogramming Flash memory: In normal operation, writing to Flash can only be done by the operating system. However, even if this protection is disabled, you can't really use Flash memory as RAM. This is because you can't set bits in Flash by writing data normally, you can only reset bits. The only way to set bits is to order a sector erase, which destroys all data in a 64-kilobyte sector by setting all the bits in that sector. So if you wrote 0 to a byte in Flash memory, that byte could no longer hold anything except a 0 until you order a full sector erase.
« Last Edit: September 21, 2011, 06:41:13 pm by Runer112 »

Offline thepenguin77

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Re: The Missing 84+ Extra RAM Pages (hardware change)
« Reply #122 on: September 21, 2011, 06:47:37 pm »
"beloved crystal" what would that mean? I have RC cars in mind,lol.

The crystal is a 32,768 Hz timer that can be utilized by assembly programmers. Internally, there are a whole bunch of scalers that let you access a very accurate frequencies with which you can do whatever you want. One of the best things about the timers though is that they will generate an interrupt when they expire, here are some things that the crystal timers have been used for.
  • Stopwatches accurate to .01 seconds over several hours
  • The sound in TI-Boy (newer versions at least)
  • Steady FPS in games
  • Determining CPU speed (~16.3Mhz on your calculator)
  • Completely flickerless grayscale
  • Playing sound with grayscale video


And without the crystal timers, none of this would be possible, or at least as accurate.

Quote
   So the calculators are 16 bit, I'm assuming that is necessary for more advanced calculations and memory sizes? I'm still studying the 8-bit principle  :P  but I'm failing to understand what issues arise with reprogramming the flash memory. I've always been told that my flash drive will eventually go corrupt from use, but after the flash memory is reprogrammed, won't the remaining memory function as RAM with out any future corruption?  Can you partition the flash memory!?   Well, now I'm gonna have to find this bespoke "low memory" GB emulator, I am a little bit excited to play Links's Awakening.  :)

Well, the flash memory actually is partitioned already. The problem is that it is partitioned in 64KB chunks which is a hardware requirement. Your flash drive probably is partitioned into 512 byte chunks which are easy to work with. And like I said, the reason it can't be effectively used as ram is because it is essentially a one time write.

A good way to look at flash would be to compare it to an etch-a-sketch. When you first start out, the entire thing is blank, then you draw you picture and you're happy with it. But lets say you make a mistake and you want to erase it, you can't. Instead, you have to shake the etch-a-sketch and clear the whole screen. This is exactly how the flash on the calculator works.

64KB chunks are huge in calculator land, 64KB is the maximum size the processor can even address, so erasing a sector of that size is not something to take lightly, especially because it takes 2 seconds. It's because of the way that flash works that we can't use is as ram. Using flash as ram isn't practical because once you write a value, it's there for good, and the only way to write another is to find some free space, which would be after your data. Then, you would just keep this up until you run out of space, at which point you have to format the entire thing and start over.
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Offline Billeekid

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Re: The Missing 84+ Extra RAM Pages (hardware change)
« Reply #123 on: September 21, 2011, 06:54:29 pm »
Technically the calculators have an 8-bit processor, as they have an instruction word size of 8 bits and the general use registers are each 8 bits. But that's not really important.

Regarding reprogramming Flash memory: In normal operation, writing to Flash can only be done by the operating system. However, even if this protection is disabled, you can't really use Flash memory as RAM. This is because you can't set bits in Flash by writing data normally, you can only reset bits. The only way to set bits is to order a sector erase, which destroys all data in a 64-kilobyte sector by setting all the bits in that sector. So if you wrote 0 to a byte in Flash memory, that byte could no longer hold anything except a 0 until you order a full sector erase.
  Sounds like I need to do a bit more research on my own, this comment sounds very technical, but some of the other replies I've read sound much to broad.  Runner112 what can I myself conclude from your reply, I apologize but right now I have no idea how to interpret this reply.  Also why did you state "Technically the calculators are 8-bit"  I could say the same for my computer, since it's operating system is also based on the 8-bit principle, I was only confused by this part of your reply.   The etch-a-sketch analogy is easier to understand.

Is the crystal comparable in function to any major component on a PC mobo?  Also wouldn't you need to use a different battery/powersource to overclock without stability issues?  Someone said something about overclocking.
« Last Edit: September 22, 2011, 02:24:50 pm by Billeekid »