intvnut Posted February 27, 2012 Share Posted February 27, 2012 Another idea... but do as you like, it's just an idea: the F18A could offer a fast RND function, one write address to set the max value and one read address to get a random number between 0 and max. If your max doesn't change, just use the read value. Yup, I thought about that, and I actually have that feature half implemented. Not sure if it will get finished though. What about just some free-running LFSRs? The TMS9900 has a MPY instruction, so you can take the LFSR output and multiply it by the size of the range and take the upper bits of the result. That part doesn't need to be in F18A hardware. For additional entropy, you could XOR in whatever's currently on the data bus each cycle. The update rule for the random number generator could then be as simple as: rng = (rng >> 1) ^ data_bus ^ (rng & 1 ? 0x8048 : 0); (0x8048 is one polynomial I happen to have memorized. There's dozens out there, and all work pretty well.) With that running at the F18A's 100MHz clock rate, it'll be way more random than anything you'd hope to generate on the TMS9900. Quote Link to comment Share on other sites More sharing options...
matthew180 Posted February 27, 2012 Author Share Posted February 27, 2012 What about just some free-running LFSRs? That's exactly what I was working on! Well, almost. I was not going to have it free running so you could set the seed and a have a reproducible list of pseudo random numbers if you need (good for debugging). Initially I was going to implement a Mersenne Twister (there is a free core available), but I didn't initially realize it requires 5 block RAMs, and I'm down to only 1 spare (the 16K chews up most of them, and the line buffers consume the rest). So, I started looking for a less resource intensive alternative and found the LFSR. I'll see what I can do about getting it worked in. Quote Link to comment Share on other sites More sharing options...
intvnut Posted February 27, 2012 Share Posted February 27, 2012 That's exactly what I was working on! Well, almost. I was not going to have it free running so you could set the seed and a have a reproducible list of pseudo random numbers if you need (good for debugging). Initially I was going to implement a Mersenne Twister (there is a free core available), but I didn't initially realize it requires 5 block RAMs, and I'm down to only 1 spare (the 16K chews up most of them, and the line buffers consume the rest). So, I started looking for a less resource intensive alternative and found the LFSR. I'll see what I can do about getting it worked in. Ah yes, reproducibility. That makes the random number generator WAAAY more complicated, since you need to know exactly how many times it's been read, and have well controlled ways of getting entropy into it. In contrast, an actual random number generator wants to get entropy anywhere it can. It's practically the enemy of reproducibility. If you want to enable a debug mode, why not just have an LSFR that only advances when read and can be reset to a known starting state with a write, and then the free-running thing with data-bus mixing for production purposes? Then it's just two different clocking modes. The MT is just an LFSR on steroids with a huge delay line, anyway, if you look at what it actually does. :-) Quote Link to comment Share on other sites More sharing options...
intvnut Posted February 27, 2012 Share Posted February 27, 2012 Ah yes, reproducibility. That makes the random number generator WAAAY more complicated, since you need to know exactly how many times it's been read, and have well controlled ways of getting entropy into it. In contrast, an actual random number generator wants to get entropy anywhere it can. It's practically the enemy of reproducibility. Or, a different thought: Just have two LSFRs. One that "free-runs" and one that advances when read. To debug your program just switch which one it uses. Switch it back once you're done debugging. On a related note, CRCs are just LSFRs + an XOR on incoming data. If the one that advances purposefully let you write a byte (which would get XORed with the LSFR value) and then advanced 8 clocks, it would also double as a CRC accelerator. Quote Link to comment Share on other sites More sharing options...
matthew180 Posted February 27, 2012 Author Share Posted February 27, 2012 If I manage to get the feature added in time, it will definitely be LSFR based, probably 32-bit with xnor taps at 32, 22, 2, and 1 based on this paper: http://www.xilinx.com/support/documentation/application_notes/xapp052.pdf See pg. 5. I will probably have a way to set the initial value, single increment, or free run. I will try to incorporate a divider so you can set a 0..n range for the result. I imagine being able to read 1 to 4 bytes of the result, and when you read the last byte it will single step to the next value, or start free running again (reading the 1st byte would stop the free running). We'll see, but I still have a few other "base" features to get done, order boards, and put the suckers together. Quote Link to comment Share on other sites More sharing options...
Tursi Posted February 27, 2012 Share Posted February 27, 2012 I think if you are going for a hardware random number generator, that reproducability need not be a design goal. A reproducable random number stream is not expensive to generate in software, but true randomness is very hard. Do existing hardware random number generators have reproducability? I thought they were free-running too. Quote Link to comment Share on other sites More sharing options...
matthew180 Posted February 27, 2012 Author Share Posted February 27, 2012 I'm really not sure, I never looked in to a hardware RNG, or at least I have never worked on a system that had one. Being able to set the seed, or set the RNG as free-running vs. stepped in the easy part. Implementing a range, which requires a hardware divide circuit, is the harder part. I have example HDL for both parts, I just have to get the time to bring them together. So I'm getting the feeling that this would be a desirable feature? Quote Link to comment Share on other sites More sharing options...
intvnut Posted February 28, 2012 Share Posted February 28, 2012 I'm really not sure, I never looked in to a hardware RNG, or at least I have never worked on a system that had one. Being able to set the seed, or set the RNG as free-running vs. stepped in the easy part. Implementing a range, which requires a hardware divide circuit, is the harder part. I have example HDL for both parts, I just have to get the time to bring them together. So I'm getting the feeling that this would be a desirable feature? Would a divide or a multiply be a better choice here? Multiplies tend to distribute any quantization bias a little more evenly. (PM me if you want more details.) Since the TMS9900 at least has both instructions, do you need either? I guess the Z80 folks will feel left out if you didn't do the scaling for them. Quote Link to comment Share on other sites More sharing options...
+Lee Stewart Posted February 28, 2012 Share Posted February 28, 2012 We have beaten on RNGs here: http://www.atariage....mber-generator/ and http://www.atariage....ly-rnd-routine/. You pretty much want an RNG to produce exactly the same sequence from the same seed that runs through the given number range in as chaotic a way as possible and with as few duplications (preferably, none) as possible. This does, indeed, aid in testing because you can pick the seed. After testing, you usually add a step that starts with an unknown seed (usually by means of a function named RANDOMIZE), periodically, or for every call to the RNG to get closest to truly random numbers. That said, there is a very good discussion on random number generation in Numerical Recipes, 3rd Edition by Press et al. ...lee Quote Link to comment Share on other sites More sharing options...
+retroclouds Posted February 29, 2012 Share Posted February 29, 2012 Hehe, seems the F18a also made some publicity on MSX.org Did generate quite some comments http://www.msx.org/news/hardware/en/msx1-video-board-f18a-13 Quote Link to comment Share on other sites More sharing options...
matthew180 Posted February 29, 2012 Author Share Posted February 29, 2012 Interesting. Thanks for pointing that out. I knew it made their news, but I didn't see the comments before. Quote Link to comment Share on other sites More sharing options...
matthew180 Posted February 29, 2012 Author Share Posted February 29, 2012 (edited) Since I'm still undecided how I'm going to format my website with documentation, here is the v1.3 feature list. Some things might change slightly, but this is the bulk of it I think. Main F18A V1.3 Features Outputs standard 640x480@60Hz analogue VGA Direct hardware pin-compatible replacement for the 9918A, 9928, and 9929 VDPs Software compatible with the 9918A VDP All four original 9918A graphics modes 80-column text mode Per-tile color in text modes Sixty-four programmable color registers with a selection from a palette of 4096 colors Enhanced color modes for 2, 4, or 8 colors for tiles and sprites Tile priority over sprites on a per-tile basis Extra attribute information per tile: flip x, flip y, transparent, and palette select Support for 30 rows in Graphics Mode I for an NES compatible display size (32x30 tiles) Enhanced name table configurations to support scrolling Horizontal and vertical scroll registers Horizontal scan line interrupt No per-line sprite limit, so all 32 sprites can be displayed on the same horizontal line Sprite linking (move multiple sprites by updating a single sprite's coordinates) Enhanced sprite collision detection information Sprite size, 8x8 or 16x16, selectable per sprite Extra attribute information per sprite: flip x, flip y Address auto-increment selectable between +1 or +32 after a read or write No CPU to VDP read or write speed limitations (up to 25MHz CPU clock speed) Original 9918A Features Not Reproduced External sync External video input Composite output 50Hz operation 4K VRAM addressing Edited February 29, 2012 by matthew180 Quote Link to comment Share on other sites More sharing options...
moulinaie Posted February 29, 2012 Share Posted February 29, 2012 This is Christmas !!!!!! Great job! Guillaume. Quote Link to comment Share on other sites More sharing options...
Willsy Posted February 29, 2012 Share Posted February 29, 2012 Wow! Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted March 2, 2012 Share Posted March 2, 2012 (edited) Hi Matthew ! i done a little article on your F18A on my website you like ? http://www.ti99iuc.i...ooooo-&Itemid=2 there is an automatic translation when you click on the flags ! Edited March 2, 2012 by ti99userclub Quote Link to comment Share on other sites More sharing options...
matthew180 Posted March 2, 2012 Author Share Posted March 2, 2012 Very nice, thanks for the extra press! The auto-translate is a nice feature, especially since I don't speak Italian. I like some of the language too, it is fun to see how some things are described in other languages and how they translate. 1 Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted March 2, 2012 Share Posted March 2, 2012 I am Happy you like .... you know, when i will got the F18A i will write a complete and detailed review as i done for the Sid Master99 Quote Link to comment Share on other sites More sharing options...
matthew180 Posted March 5, 2012 Author Share Posted March 5, 2012 UPDATE: A week late, I know, I apologize. Since the minimum order to have the F18A manufactured was not met, I have decided I can handle the quantity myself and I will be doing all the assembly. This will slow down the delivery a little, but not too much I hope. Boards and parts have been ordered, and once they come in I will begin fulfilling the F18A orders in the order they were received. Since the orders are not overwhelming, I'm going to leave the pre-orders active for now. I plan to make a few extra boards which will be on sale after the pre-ordres have been fulfilled, and beyond that I will consider making boards on an as-needed basis. My plan is to make the F18A available to everyone who wants one. Thank you everyone for your support and patience, but the waiting is almost over! :-) 2 Quote Link to comment Share on other sites More sharing options...
Cory Posted March 6, 2012 Share Posted March 6, 2012 (edited) UPDATE: A week late, I know, I apologize. Since the minimum order to have the F18A manufactured was not met, I have decided I can handle the quantity myself and I will be doing all the assembly. This will slow down the delivery a little, but not too much I hope. Boards and parts have been ordered, and once they come in I will begin fulfilling the F18A orders in the order they were received. Since the orders are not overwhelming, I'm going to leave the pre-orders active for now. I plan to make a few extra boards which will be on sale after the pre-ordres have been fulfilled, and beyond that I will consider making boards on an as-needed basis. My plan is to make the F18A available to everyone who wants one. Thank you everyone for your support and patience, but the waiting is almost over! :-) If you're looking for help, I'm happy to offer my board assembly and soldering skills to the effort. Edited March 6, 2012 by Cory 1 Quote Link to comment Share on other sites More sharing options...
matthew180 Posted March 7, 2012 Author Share Posted March 7, 2012 If you're looking for help, I'm happy to offer my board assembly and soldering skills to the effort. I'll see how it goes first, but I might just take you up on that. Thanks for the offer. By the way, did you ever get your disk controller working? Quote Link to comment Share on other sites More sharing options...
Cory Posted March 10, 2012 Share Posted March 10, 2012 I'll see how it goes first, but I might just take you up on that. Thanks for the offer. By the way, did you ever get your disk controller working? No, but I did isolate the problem down to a blown buffer. I just never got around to replacing it. The excitement was in the hunt for the problem. I still intend to replace it, but more exciting projects have taken its place. Quote Link to comment Share on other sites More sharing options...
matthew180 Posted March 16, 2012 Author Share Posted March 16, 2012 Update: The boards came in yesterday. Now I'm just waiting on a few parts and I can begin some assembly! 5 Quote Link to comment Share on other sites More sharing options...
Cory Posted March 17, 2012 Share Posted March 17, 2012 I think I see mine. Isn't it the one 2nd from the left? Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted March 17, 2012 Share Posted March 17, 2012 Pretty. Quote Link to comment Share on other sites More sharing options...
opcode Posted March 17, 2012 Share Posted March 17, 2012 I cannot wait to get mine.... Quote Link to comment Share on other sites More sharing options...
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