Maury Markowitz
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Posts posted by Maury Markowitz
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Oh yeah, while I'm here, what was the PROCEED pin used for?
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Just a few details off the top of my head. The cassette deck has FSK decoding built in, but not encoding. So, channels 1 and 2 are set to the FSK frequencies which are sent on SIO pin 5 instead of the data bits in 2-tone mode. These tones go straight to the head in record mode. The 410 has frequency detectors for playback to convert the audio to a normal bit stream.
Most excellent Bryan, this is very helpful!
The clock signal is present as an output on the mode that the OS uses by default.
It's not used even by the disk drives, most use bit-banging software delay between bit reads.
For cassette operations the clock is irrelevant. Tape blocks use the 2 speed measurement bytes $55,$55 (lsb is transmitted first). Software monitors the bitstream and uses the time elapsed to lookup a table containing input bitrate settings for AUDF3/4. This is mainly to compensate for tape stretch but also allows custom tape bitrates to be read without extra software.
You use a few terms I'm not familiar with. So let me explain what I understood from the manual and perhaps you can point out where I go wrong.
As I read it, the programmer would set the base clock rates using the audio channels.
Then the POKEY would read or write bits from the shift register on every assert of the clock.
When the register completed the 10-bit read/write, it did an NMI for more data.
Is this correct?
I have not heard the term "bit-banging" before.
I believe the last part you are saying the system used an async read/write, basing the rate stored in $55,$55 ($56?). Is this a "clockless mode" that was used in async modes?
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Name me a computer before 1979 that had dedicated video processors and a dedicated sound chip? Yes, video cards and sound boards became popular in the 80's, but Atari got there first. My comment about it taking almost 20 years for the industry to adopt was aimed at the SIO. USB didn't become mainstream until well in to the 90's.
There were, of course, many similar systems long before USB. I can thing of Access.Bus, AppleBus and Apple Desktop Bus off the top of my head. No, the later two are not the same thing, AppleBus was literally USB in every way except the connector, but was not released (sadly), and thus ADB was introduced to fill that niche.
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A number of ROMs include code to speed up math routines - Omni had one IIRC and I recall another as well.
Does anyone know exactly what these routines did in order to run faster? I recall Bill Wilkinson telling me the original routines were written by "the new guy" and could have been much faster, but I am not clear if this is what they did.
Likewise, these same ROMs often included graphics speedups... similar question, does anyone know what exactly these did?
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I'm reading over the hardware manual, and if I'm reading it correctly the system wrote to tape by connecting either channel 1 or channel 2 of the POKEY to the data pins if a particular bit was a 1 or 0. However...
1) normally a bit was triggered to the data pins from the shift register when the clock pins went high. But that clock was driven off a POKEY channel. So where was the clock signal for the cassette write? in channels 3 and 4?
2) normally the signal from the POKEY went to the clock pins. Was this true here as well, and the 410/1010 read those pins instead of the data pins?
3) a post here states that the *reading* was accomplished in the deck itself using narrow bandpass filters. if that is the case, what was the output? async bits on the DATA pins?
4) what were the two frequencies for mark and space.
Also speculation: given this system, would it not have been possible to make a modem that used POKEY as the A/D?
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I'm writing a Wiki article on the CX40, and using it as the basis for a wider discussion on digital joysticks in general.
I'm really lacking any sort of images of the internals, especially the CX40.
If you have any Atari-style stick that's opened up and you're wiling to donate a couple of images, I'd greatly appreciate it!
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Does anyone have a source that indicates the total production of the CX40 joystick? I assume it is well into the millions, but I'd like a solid number.
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Bump. Look at the FCC Class. It should be Class C - for consumer - not Class B [business]. All "home computers and consoles of the time had to be C certified in order to connect to a TV. Class C caused the A8 line to not have internal expansion slots like the Apple // line. Why on Earth is this Class B on a 5200?
So as far as I can tell, there is no Class C. At least none of the FCC documents I can find have such a thing. They have only two such classes, Class A and B. A is for industrial devices and is the less stringent of the two. It mostly covers devices that will be used in electrical noisy environments so as long as the leakage is low it won't have much of an effect anyway. Class B is for consumer devices and is much harder to meet. It demands that interference from the device will not effect other devices around the home.
Reading over various materials, it appears that the standard Atari built to was somewhat overdesigned. Bushnell later commented that the standard had "no teeth", but it's not clear what this means. It is clear the later machines had much less shielding and met a greatly reduced standard of some sort, but it's not clear whether that was due to matching a different standard entirely, the standard being changed, or people just ignoring it.
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Does anyone recall the name of the relatively popular early 8-bit game that had a Qix-like "snake" circling the middle of the screen while you were at the bottom shooting it with a sort of space-invaders like ship? I recall that after a while the snake would grow eyes, a tail, etc, adding to the action on the screen.
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I suspect that the problem with Amy was that it…
1) didn't do everything the POKEY did, so you still needed one of those
2) wasn't ready in time for the rushed production of the ST
Sad, in the end, as the Atari line's sound performance suffered in comparison to its competition throughout this period.
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Landon Dyer was very dismissive of the Sierra and Gaza projects in his blog,
Ohh, do you have a URL for this? Google isn't turning anything up of interest.
The dual-m68k is likely a canard. Any such device would have *serious* bus contention issues. You could do it, but the two CPUs would have to be isolated, and likely on their own RAM/bus. So maybe a CPU dedicated to the graphics or something, but that seems extremely unlikely given the costs. It wasn't until the 020 that multiprocessing became practical, and even then I know of very few machines that actually attempted it.
JerryM sent me a few things that suggest that the Sierra was definitely single-CPU, but the decision had not been made as to which one - 286 and m68k were both being considered. Curt has a block diagram showing a single CPU machine, with the NS32016 in it.
Curt has mentioned in other threads that there aren't any [known] surviving screen shots of the Snowcap GUI that was planned for those computers running atop BSD [and not UNIX].
According to JackP, the entire OS was just a paper project when it died. Unix was being "discussed" but it seems very little progress had been carried out.
The OS team are the only ones I haven't tracked down so far.
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My pleasure!
Now if someone could figure out the one I'm looking for…
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The character you controlled looked like he was a robot or a guy in a slim spacesuit, wearing a helmet with a black faceplate and the a red uniform/spacesuit. I could never figure out the point of the game, I only remember walking the character up to a door and it sliding up to open.
You are almost certainly thinking of Brataccas.
https://en.wikipedia.org/wiki/Brataccas
Great idea, absolutely terrible implementation. The game was basically completely unplayable due to control lag. I recall playing the game like mad in the hopes that it would eventually "work". It didn't.
All combat was sword play, which invariably degenerated into the characters running past each other while slowly swinging, invariably missing and often running right off the screen into another room. In spite of all the manual's warnings about playing it safe, I found that combat was so poorly implemented I could attack everyone and then walk around with the entire base swinging madly at me while nothing happened.
Worse, there was no indication of how you were supposed to win. I only learned how to win the game after the invention of the internet, when it became possible to look it up. As it turns out, I was one step away from winning, I simply had to walk through a particular door! No loss in the end, all it does when you win is show the credits.
Now normally a bad game is a bad game. But Alan Kay once said the Mac was the first computer worth complaining about, and likewise, Brataccas was the first game (of it's genre) worth complaining about. ONE SENTENCE in the manual would have cleared up the confusion about how to actually play it, and the dynamics obviously could have been fixed with some tuning.
Why bother? Because this was the first truly real-time GUI-based adventure game. You interacted with the other characters using menus, you could pick things up from the ground, and when you killed someone (which *was* possible, albeit random) they dropped everything. In *theory* this was an amazing game. But it wasn't. *sigh*
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Ok here's mine.
Atari 8-bit game, sold mail-order. You were a space-invaders-like ship at the bottom firing up. Your main opponent was a Qix-like "snake" that periodically dropped objects on you. As your score increased, the snake added a tail, which would later break off and go flying around the screen. Apparently later versions added more events, like meteors.
This one is interesting to me because I know it was written in my home town in Toronto. The address for the email is on a major through-route in the city, and I've passed the row-home many times and wondered if I should go knock on the door…
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Hi guys,
I'm the author of the Wiki article on the Amy, and if you haven't seen it lately, I've added all sorts of changes, so enjoy!
I was wondering if there is *anything* concrete about any of the 8-bit replacement projects. What I have found, mostly through email conversations with some of the engineers, is that none of the machines really existed beyond mockups. One engineer is even unsure whether Sierra had finally decided to use the 286 or m68k.
The only think I've been able to actually document is the Amy, which was helped in no small part due to a lawsuit. I'm worried but hopeful that some sort of engineering documentation from either Sierra or Gaza (assuming they weren't the same thing) still exists in someone's closet.
So here's the names I've heard, and I'd love to hear anyone's input…
Gaza - 68k based machine with Silver and Gold GPU and Amy sound
Sierra - 286 or dual m68k machine (seems unlikely!), Rainbow GPU, Amy sound, Eva OS
Eva - concept for the Sierra OS, existed only in theory. Main designer was apparently considering Unix V port
Silver and Gold - GPU for Gaza? Zero information on this
Rainbow - GPU for Sierra, and possibly other projects
Amy - the only part to be released
I have seen mentions of a new GUI and a different OS as well, here in the forums.
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Survivor by Synapse. It might have been the first one. Not the most interesting game though.
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As for Gil and Apple, wasn't the iMac started under Gil's reign yet Jobs receives all the credit for it?
True in fact, but not in spirit. What became the iMac was one of many products being cooked up at Apple, all of which were canceled because they were "too weird". Some of these would make it out in limited numbers, only to be killed off weeks later. As a result, the company appeared to be skitzo, and everyone avoided it like the plague.
So would GIl have released it? No way. Consider:
Scully was all about making the Mac go "high right" and selling to business
Spindler was all about selling the company off
Amelio was all about shedding people and getting profitable
None of these guys would have done the iMac.
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If you really wanted to "save" Atari, you'd need to take a time machine back to late 1981, and fix the 1200XL and the 5200 before they launched in '82.
Bingo. That was the point where I think things went south on them. This machine was a marketing disaster, and _right_ at the worst possible time. Had it done even a little better they would have had time to move production overseas without killing the entire line while that happened.
By the time the Tramiels arrived I don't think Atari was Atari any more. More like the bloated pig that Microsoft is today, or Apple was in the 90s - developer heavy, lurching from project to project, developing lots of things people don't actually want because they said they did in a poll.
The sad thing is the ST. Having owned and used one for a long time, I can say without hesitation that it was least favorite computer. There was no "design" behind it, just a bunch of off-the-shelf bits shoveled together into a box as cheap as possible. Not that that's a bad thing, but it was no Atari.
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Did anyone here actually play this game? It came out right as the market was imploding, and as I didn't have a floppy, I never had a chance to run it.
Later I was looking over some old ANALOGs and saw a review for a game that I _think_ was called "Space Cowboy" that appeared to be one of the levels of Jupiter Mission. Was Jupiter Mission just a bunch of other games shoveled together?
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I'm looking for a reasonable quality picture of a few different flatbed plotters for my article on wikipedia.org. I figured this was as good a place as any to ask. Does anyone has a scan of a "classic" flatbed like one of the early Roland machines, or know of one on the web somewhere?
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Maury,Excellent article! I did not know about the wikipedia at all. It still amazes me that a CPU could have such staying power. Granted that its in a different niche but still around after 25 years
Yeah, the wiki kicks ass. It's definitely the best thing to come along since google.
Maury
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Just in case you thought the 6502 was old and no longer used:http://www.westerndesigncenter.com/about.html
Apparently they still sell a few hundred thousand a year for toys, cars, appliances etc.
Funny, because I was just talking to him on the phone yesterday for my wikipedia article. He said the main use now is medical equipment controllers, followed by car dashboards, and then modems.
http://www.wikipedia.org/wiki/MOS_Technologies
Maury
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Not supplied The next random number in the sequence.Ah-ha! Thanks.
Maury
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Math speedup ROMs
in Atari 8-Bit Computers
Posted
Great info phaeron! I do recall people using the timing of the various draw routines as a way to time things, which was kind of dumb when you consider you had a fairly good clock in the video system that you could use.
And you too thorfdbg, that is precisely the sort of explanation I was looking for.
Rybags, that thing you read is perhaps something I wrote. About a decade ago I had a nice conversation with Bill and wrote up a little web page - text only - about what I learned. The info from that has been diffusing out ever since. Basically, the book they were using didn't have multiply and divide, so instead of writing routines for this, the guy they had doing it just looped adds. Bill seemed a bit embarrassed about that one (as much as one can gleam from an email anyway).