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Post by kaos116 on Mar 9, 2006 21:03:58 GMT -5
I have been putting together some design goals for new 8 bit retro. I have listed the top 5 here and why those choices. If anyone has any input I'd love to hear it. Sometimes I get tunnel vision and lose sight of the over all goal, which is having fun :-D
1. Must be buildable from easily obtainable ICs Most of what will make it work will be done in software.
2. Will use 30 or 72 pin SIMMS. Who doesn't have this hanging around?
3. VGA monitor output. Possibly NTSC/PAL in the future, but the video timing is easier with VGA and I beleive it's universal world wide
4. 3-5 Addon ports for upgrading. This way it can be built in stages. Build the basic unit then create addon cards for the extras.
5. Here is the one I like. Compact flash cards that will hold the OS/Emulator/Programs. Let me explain this idea. The computer will be universal. You will have the ability to insert a CF card that will emulate your machine of choice. If you want a C64, pop that card in. Want a TRS-80 COCO2? Pop that card in. The other requirement with the CF cards is that they will be Fat16 compatible. So, you will be able to connect them to your PC, load as many platform executables as the card will hold and you pop it in the retro. It will be accessed just as you would a floppy drive for what ever platform you are emulating.
Some other goals. Small footprint, self contained except for the monitor, single voltage power supply, no moving parts (fans/drive motors), and of course having fun with it!!!!
I have a question for the group. I have never had a tape drive and a floppy drive for the same computer. Is it possible to load programs off cassette tape and then save them to a floppy?
Ok... I am off to step one. Keyboard interface.
Todd
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Post by Golan Klinger on Mar 9, 2006 21:18:36 GMT -5
I have never had a tape drive and a floppy drive for the same computer. Is it possible to load programs off cassette tape and then save them to a floppy? Sure. Once something is in memory it shouldn't be very difficult to save it out to disk provided one has the right tools. What did you have in mind?
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Post by kaos116 on Mar 9, 2006 22:27:49 GMT -5
I have seen CD's on the big auction site that have 100's of software titles on them, mainly for the TRS-80, if you read the fine print you find out that these are MP3/wav files of the screaching audio from the cassette versions. I am just wondering how difficult it would be to get them on to a disk. It might be easier to convert them on a modern day PC to some sort of disk image.
I have a few Timex/Sinclair 1000 titles on cassette too, that I would like to get into a 'hard' version. I have read about trying to archive the older software and I guess some people have been recording their cassettes to MP3 or WAV files. They don't degrade in that format.
BUT...... With the above project in mind. It would be nice to be able to get to use some software titles that are ONLY on cassette.
I am not sure I am making sense. It's getting late :-D
Todd
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Post by Golan Klinger on Mar 9, 2006 23:22:10 GMT -5
This is the first time I've heard of CDs that contain mp3s/wavs of software. It's an interesting idea. It would be simple enough to get the data to tape and from there to disk. What we be even cooler is if there was software to convert the sounds directly to program form. Not a simple program to write though. At any rate, I'm not sure I know what this has to do with designing an 8 bit computer...
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Post by kaos116 on Mar 10, 2006 2:20:44 GMT -5
Well, it has to do with the 8 bit design in the fact that I have a good working knowledge of the Z80 processor. This is probably going to be the first emulator package I am going to write for the new 8bit. But the only software I have is on cassette. This part of the project is a ways off, but I figured I'd start asking questions now. I am going to have to write a simple OS for the new 8 bit for testing of the hardware. The final production will probably use some sort of boot loader to load the other platforms. Maybe I'll just pick up a floppy for my COCO and do some testing with cassette to floppy transfering. Then again I could always add a cassette interface to the new one
I need to come up with a name for this new 8 bit. It's just refered to around here as the 'computer thing'
Todd
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Post by thurstan on Mar 10, 2006 5:18:07 GMT -5
Hey Kaos116, this sounds like an exciting project! Its great that people have moved from bedroom homebrew software to bedroom homebrew hardware!
Any idea of what you will use for a keyboard? Possible to design a new one to give it a different feel? I've seen lots of projects that utilise PC keyboards, but I end up thinking "this feels like an emulator on a PC" and not a different retro machine. But then again nigh on everyone has a PS/2 keyboard at home.
As for a name, thats a tricky one. Do you want to have a professional sounding name or have a name that reflects its homebrew/home hacker origins?
I reckon you should definitely include the amount of memory in the name like C64,Amstrad 6128 or RetroMac 32 to give it a retro flavour
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Post by miner2049er on Mar 10, 2006 6:56:43 GMT -5
Using Flash media for the interchangeable OSs is a great idea.
I have found that they tend to need more defragging than standard drives though.
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Post by thurstan on Mar 10, 2006 7:17:54 GMT -5
Also is there any issue over the number of writes they can handle in their lifetime? Or is it not worth worrying about?
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Post by Golan Klinger on Mar 10, 2006 11:57:10 GMT -5
Also is there any issue over the number of writes they can handle in their lifetime? Or is it not worth worrying about? I brought that issue up in the DTVHacking board once and the conclusion that others had drawn was that there are enough read/write cycles to last years and years for most people and that with the price of flash cards being what they are (and getting cheaper all the time) that the issue was, well, a non-issue. I had to agree. I also have to agree that flash cards are today's equivalent of floppies. They're small and portable, cheap, universal and fairly reliable. Definitely the way to go.
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Post by kaos116 on Mar 10, 2006 17:42:14 GMT -5
Hi everyone, The keyboard that I am using is from a TI99/4a. I am using this one because I like the feel of the keys and it's smaller than some others in the fact it doesn't have many extra keys. The keyboard interface will be easy to write for any keyboard. As I have it on paper now as long as the header for the keyboard is not more than 16 pins it should be easy to interface. I could always use a chip with a bigger pin count to allow for bigger headers. I'll have to pull some of the other retros apart and see how many pins they have. Adapting it to a PS2 keyboard is simple too, but I agree.... it wouldn't feel retro. The CF read write issue has been looked into in the past for another project. From the manufactures I have an unofficial word of 1/2 mil +. It's also writing that is the issue. Reading it is not such a strain on it. So some quick math. Lets say 50 cycles a day divided by the advertised 100K cycles = 2000 days or 5 1/2 years. I can live with that. As far as the name goes. I liked the idea of having the memory size in the name, but it's going to be dependant on what the builder has in his junk box. I want to try to use 30 pin simms, but I am not sure they are fast enough and IIRC they max out at 16M. 72 pin simms are going to be easier to find than 30p in a few years and would definately be fast enough. I have some 128M around here somewhere, but they are harder to interface with an 8 bit system. Not impossible, just harder. There is only going to be 1 memory (ram)slot for simplicity and size of the board. Not sure on the video ram yet. If it's going to be shared. The Microcontroller I am using for the brains is the 18F4620 by Microchip. www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1335&dDocName=en010304A name will come in time as the project takes shape. Todd
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detnyre
Junior Member
detnyre
Posts: 99
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Post by detnyre on Mar 10, 2006 22:26:02 GMT -5
It would be cool if it would have basic ethernet connectivity.
Are you thinking about having BASIC in ROM or have it run some type of operating system?
Do you have a website that shows your plans so far?
Derek
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Post by kaos116 on Mar 11, 2006 12:11:56 GMT -5
Ethernet could certainly be done with an add on card.
Basic in ROM.... Hmmm. That would be great if there is enough room left in ROM. The only required firmware that is needed is the bootloader. Which is a tiny bit of code. I also wanted to have a simple OS. That would allow you to change CF cards and not have to reboot the machine. When you would unplug a card it would default back to this simple OS allowing you to start up another card. I am not sure that is going to happen because of some of the restrictions on the bootloader. But that is a bridge who's time to cross will come. What does this have to do with BASIC in rom? The size of the ROM and if I can fit a useful one in. I could add additional rom space for a default OS with BASIC. It could check for a CF card and one isn't present it could default to that one.... Hmmm something to think about.
No website of yet, but along with you, my girlfriend has suggested that I start one, or atleast a blog somewhere. Maybe I can get her involved and get her to do that part ;-)
I did get the keyboard interface working. What I need is to find a way to secure it to something. It's just sliding all of the work top. I guess the next step is to build a cabinet of sorts.
Todd
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