• If you ever wondered about weather predictions

    Eric Hertz12/22/2022 at 07:24 0 comments

  • Hard Disk vs VHS reality-check

    Eric Hertz12/12/2022 at 06:05 0 comments

    There used to be special ISA cards that allowed for connecting a VCR to a PC in order to use the VCR as a tape-backup.

    I always thought that was "cool" from a technological standpoint, but a bit gimmicky. I mean, sure, you could do the same with a bunch of audio cassettes if you're patient.


    But, actually, I've done some quick research/math and think it may not have been so ridiculous, after-all.

    In fact, it was probably *much* faster than most tape-backup drives at the time, due to its helical heads. And certainly a single VHS tape could store far more data. (nevermind their being cheap, back then).

    In fact, the numbers suggest videocassettes were pretty-much on-par with spinning platters from half a decade later in many ways.



    I somehow was under the impression the head on a VHS scans one *line* of the picture each time it passes the tape. But, apparently it actually scans an entire frame. At 60Hz!

    In Spinning-platter-terms, it'd be the equivalent of a hard disk spinning at 3600RPM. Sure, not blisteringly fast, but not the order-of-magnitude difference I was expecting.

    The video bandwidth is 3MHz, which may again seem slow, but again, consider that hard drives from half a decade later were limited to 5MHz, and probably didn't reach that before IDE replaced them...

    "The limited bandwidth of the data cable was not an issue at the time and is not the factor that limited the performance of the system."


    I'm losing steam.


    But this came up as a result of thinking about how to archive old hard drives' data without having a functioning computer/OS/interface-card to do-so.

    "The ST506 interface between the controller and drive was derived from the Shugart Associates SA1000 interface,[5] which was in turn based upon the floppy disk drive interface,[6] thereby making disk controller design relatively easy."

    First-off, it wouldn't be too difficult to nearly directly interface two drives of these sorts to each other, with a simple microcontroller (or, frankly, a handful of TTL logic) inbetween to watch index pulses and control stepping, head-selects, and write-gates. After that, the original drive's "read data" output could be wired directly to the destination's "write data" input. Thus copying from an older/smaller drive to a newer/larger one with no host inbetween.

    It's got its caveats... E.G. The new drive would only be usable in place of the original, on the original's controller, *as though* it was the original drive.

    The new drive has to have equal or more cylinders and heads. It has to spin at exactly the same rate, or slower. Its magnetic coating has to handle the recording density (especially, again, if it spins slower).

    BUT: it could be done. Which might be good reason to keep a later-model drive like these around if you're into retro stuff. I'm betting some of the drives from that era can even adjust their spin-rate with a potentiometer.


    Anyhow, again, I've a lot to cover, but I'm really losing steam.


    Enter the thoughts on using VHS as an only slightly more difficult-to-interface direct-track-copying method... as long as the drive (maybe Shugart or early MFM? is within the VHS's abilities, which it seems there may very well be such drives in retro-gurus' hands.

    So, herein, say you've got a 5MB mini-fridge-sized drive with an AC spindle-motor (which just happens to spin at 3600RPM, hmm). Heh...

    Anyhow, I guess it's ridiculous these days, each track could be recorded directly to a PC via a USB logic analyzer, right? (certainly with #sdramThingZero - 133MS/s 32-bit Logic Analyzer

    Or isn't there something like that already for floppies ("something-flux").

    Anyhow, I guess the main point is that storing/transferring the flux-transitions in "analog" [wherein I mean *temporally*] has the benefit of not needing to know details...

    Read more »

  • "The Next Bill Gates"

    Eric Hertz12/06/2022 at 20:44 0 comments

    When I was a kid, I heard this often...

    Lacking in mutually-understood history and details of technicalities, it took me years to try to explain "Well, more like Steve Wozniac." And literally decades to realize how *that* was probably misinterpretted.

    So, bare with me as I try to reexplain to several different audiences simultaneously.

    First, OK, everyone knows Billy-G. I shouldn't have to explain that one, but I will.

    As I Understand (I'm no history-buff):

    Billy-G didn't design computers nor electronic circuits; he did software *for* computers. And his real claim to fame was actually software he *bought* (not wrote) from someone else.

    Most folk who made the statement about me being "The Next" weren't aware of Stevie-W...

    Stevie-W, unlike Billy-G, did electronics design, the actual computers themselves. That's a fundamental difference I was trying to get across, but couldn't convey in terms that really struck a chord. 

    In their minds, I gathered over many following years, the two were basically one-and-the-same, just from different companies. And the latter, then, was the "runner-up" that few outside the nerddom even know by name.

    Not quite.

    Billy-G: Software

    Stevie-W: Mostly Hardware

    Fundamentally different sorts of people. Fundamentally different skills. Fundamentally different aspects of computing. Maybe like comparing a finish-carpenter to a brick-layer. 

    Both, mind you, can be quite skilled, and the good ones highly revered. But therein lies the next problem in trying to explain to folk not already in-the-know: It seems many, again, associate a statement like that the wrong-way compared to my intent; thinking something like "oh, finish carpenters are concerned with minute *details*, whereas brick-layers are concerned with 'getting er done'" ish... I dunno what-all other people think, but I know I was yet-again misunderstood when I made such comparisons, so let me try to re-explain:

    Well, no. My point wasn't some judgement of the skill-level or quality of craftsmanship or even about the utilitarian importance/necessity of what they do. My point was that what they do are both related to construction, but that we generally hire both when we build a house; because one is good at one thing, and the other is good at the other. 

    Maybe I should've chosen electricians and plumbers as the example, instead. But I'll never finish this if I open that can of worms.

    Billy-G: Software that the end-user sees

    Stevie-W: Hardware, and software in the background that most folk these days don't even know exists.

    Which, probably, goes a ways in explaining why so many folk know the former, since his stuff is in your face, while the latter's stuff is encased in beige boxes.


    Now, during *years* of trying to figure out how to explain this fundamental difference, without *ever* getting far-enough in the conversation to make my *main* point, the end-takeaway often seemed to be "The Next Steve Wozniac." At which point I was so friggin' exhausted... ugh.


    So, for years I tried [and obviously failed] to rewire my brain to at least get that fundamental concept across to such folk concisely, *so that* I could maybe finally get across the next point:


    There were MANY folk, probably *thousands,* doing what Stevie-W was doing before he and his work got "picked."


    Now, when I say *that*, folk tend to, it seems, think I'm looking to "get picked." And, I suppose I can understand why they might come to such a conclusion (despite the fact we're nowhere near far-enough along in this discussion for conclusions to be jumped to) because I had to try to work on their level, and explain fundamental concepts from a perspective I thought they understood... which... apparently to me, requires names of celebrities to even be bothered to try to understand. Hey, I'm not claiming that *is* the way they are, I'm saying that as someone who has dedicated a huge portion of my life's brainpower to something...

    Read more »

  • Reusing mask/OTP-ROM uCs

    Eric Hertz12/02/2022 at 23:45 10 comments

    The 8x51 series *has* internal ROM, even the 8051. The 8031/8032 are allegedly "ROMless" versions of the 8x51/52.

    What that means to designers/hobbiests is, e.g.: 

    You can design for an 8031, with an external ROM, then drop-in any old 8x51, even if its (OTP, mask, etc.) ROM was programmed with code from an entirely different product, or buggy, or whatever.
    Find some old 8x51 in some old piece of trash, think it's worthless because it's already been programmed...? Tie one pin to a voltage rail and use it as an 8031 in your own project.

    What that probably meant from Intel's perspective:

    "Hey, a customer ordered a bunch of preprogrammed 8051's, but discovered a bug before we shipped" and/or "We got a batch of 8051's with flaky ROMs" and "we're sitting on 1000's of otherwise useless 8051's. What should we do with them?" "Remarket them as ROMless 8031's, and let the new customer supply their own ROM chip!"

    Forward-thinking, reusability, reduction of eWaste...

    And, in this new era of old paper datasheets now scanned and uploaded as pdfs (as opposed to my earlier experience where pdfs only existed for products designed in the pdf-era (THANK YOU to those who take the time and provide that effort!)), I've discovered that many previously zero-search-result ICs on old PCBs scavenged from VCRs, CD players, TVs, Stereo Components, and whatnot, now have full-on datasheets detailed down to instruction-sets and hex operands... 

    And many of those, similar to the 8051, have a pin which can be tied to a voltage rail to disable the internal mask-ROM, enabling them, like the 8031, to run off an external ROM.

    Wow! SO MANY uC designers, of so many various architectures, even 4-bit, considered this worthwhile! And even if it was purely because they wanted to sell otherwise defective/wrongly-programmed uCs, it *still* benefits the likes of the customer and even the alleged us, that are hardware hackers.

    I dunno, I thought it was darn-relevant in the "chip shortage era."

    [Inspired by the lack of response to my comment at https://hackaday.com/2022/12/01/ask-hackaday-when-it-comes-to-processors-how-far-back-can-you-go/ and the fact it seems to be blocking my adding the above as a clarification-reply.

    Fact is, I've been meaning to document my box full of scavenged PCBs with such uCs, and maybe even turn each into a "NOPulator"]


    Oh, it finally appeared there, twice, numerous hours later. Heh.

    I even got a response suggesting looking into Collapse OS: http://collapseos.org/

    (Very Intriguing).


    Lots more thoughts and My Collection, now over at:

    #Repurposing OTP/mask-ROM microcontrollers 

  • Just because you may doesn't mean you should

    Eric Hertz12/01/2022 at 09:28 4 comments

    I wonder how many folk training AI have never even trained a dog to shake.

  • Superconductor Levitation: Quantum Locking Explained

    Eric Hertz05/03/2022 at 01:10 0 comments

  • e=mc^2 ?

    Eric Hertz05/02/2022 at 18:54 0 comments

    What IS The Speed of Light Squared?

    What IS Distance Squared Over Time Squared... ?

    What is Time Squared?!

    Dunno, BUT:

    Well, Acceleration is Distance Over Time Squared...

    And Distance Squared is Area

    So might Speed Squared be The Acceleration Of Area?


    "The Acceleration of Area Is Constant" ?

    If you were to release a ball down a ramp, its acceleration would be constant, (assuming constant gravity and constant slope).

    If you drop a rock in a pond, the ripples propagate outward at a constant speed along the radius... But, interestingly, the Circumference of the ripple has a constant "acceleration" (distance over time squared)

    If you were to create a "ripple" in three-D space, say by exploding some TNT in midair, the sound of the explosion would propagate at a constant speed radially in all directions, at the speed of sound... The surface-area of that 3D "ripple" would have a constant acceleration.

    So, if all the energy in some mass were released instantaneously, it would create a spherical wavefront whose surface-area would "accelerate" at a constant rate.

    E= MC^2

    So, then... Energy is usually electromagnetic, right? And ripples in  electromagnetic fields travel at the speed of light...

    So E=MC^2 basically says that if you were to instantaneously release all the energy that a mass *can* contain into a burst of electromagnetic energy, then that energy would propagate as an electromagnetic wave-front which has a constant "acceleration of surface area". I.E. a /sphere/ (?)


    Now, if we think of it this way, and we change our units of time and speed from meters and seconds to something instead related to the propagation of this wavefront, we'll find that the "constant acceleration of surface-area" (i.e. C^2) Is Directly Related to Pi^2, and thus the speed of light (radially) is in fact an integer constant times Pi. (?!)


    Musings not yet verified.

    Note that I later found an article about a  relationship between Pi and C, which derives it through the half-period of a pendulum. Unfortunately, I'm not sure the math works-out, due to the fact that a pendulum's period is not /exactly/ as stated, but only /very close/, under some conditions. However, the fact is those /specific/ conditions seem to come /very close/ to equating C to Pi, in a very similar way as my wavefront-propagation theory does.


    So, what are the implications?

    Dunno, haven't had time to really look into it, yet.

    However, one path seems to suggest that gravity, too, is directly related to C^2 (and thus Pi^2), which makes sense if considering, again, the idea of the surface-area of a wavefront's propagation. 

    Imagine a brief "pulse" of gravity as the opposite of an electromagnetic explosion... An implosion(?). Its wavefront (pulled into its center, rather than extending away from it) would have a constant acceleration (of surface-area). 

    So, now, imagine a constant flow of such energy, much like a constantly-lit lightbulb...


    I dunno where it goes!

    Here's a weird thought just popped-up...

    Gravity doesn't /do/ anything, unless there's another object involved. So, until another object comes into the path of its (impulse) "wavefront," that wavefront exists everywhere on the sperical surface. But, when an object comes into its path, does that spherical surface "collapse" onto that object? Much like they suggest a photon may propagate outward in every direction spherically /until/ it hits something? At which point that sphere collapses onto that object, much like an expanding bubble in bubblegum "rubberbands" (spherically!) back to one's face?



  • Parallel Resistors

    Eric Hertz05/02/2022 at 17:59 0 comments

    Think of Conductivity, instead.

    Two parallel conductors will conduct better than one...

         = Conductivity(R1)
            + Conductivity(R2)
            + Conductivity(R3)
            + ....

    Conductivity of a resistor = 1 / Resistance

    WAY easier to remember, intuit, (and calculate?) than 1/Rt = 1/R1 + 1/R2 + 1/R3 ...