Oldskooler Ramblings

the unlikely child born of the home computer wars

Comedy gold in the Handy specification

Posted by Trixter on August 12, 2015

The Atari Lynx is my favorite handheld console.  Planning and design started in 1986, long before the Nintendo Game Boy, but development took long enough that it was actually released half a year after the Game Boy.  Whether or not that makes it the first or second handheld console is up for discussion, but it was definitely one of the first two.

History shows that the Lynx had an unsuccessful run compared to other handheld consoles of the time, which includes the Game Boy, Game Gear, and TurboExpress.  Lynx’s failure in the market was split fairly evenly between three culprits:

  1. Price: $179 vs. Game Boy’s $100
  2. Battery life: It took 6 AAs to power the unit for only 4 hours
  3. A lack of compelling licensed or original titles

The first hardware revision was also somewhat large, but as a guy with large hands, that never bothered me.

There were some killer arcade ports to the Lynx that really showcased what the system was capable of, such as Road Blasters, Stun Runner, and Klax.  But these were ports of Atari games; Lynx never got the “big” licensees such as Mortal Kombat or Street Fighter (a double shame considering the Lynx supported true hardware multiplayer linkups).

I recently sought out the Lynx hardware specification so that I could reminisce, sadly, about all of the untapped power Lynx had that was never realized.  The Lynx was so powerful that it shamed other handhelds for nearly a decade after it was discontinued:

  • 4096-color palette
  • Unlimited sprites with scaling, clipping, and collision (multiple modes!) all performed in hardware
  • 4-channel stereo sound supporting both algorithmic and sampled waveforms (in other words, it could play both pure-hardware chiptunes and Amiga mods)
  • Multiplayer cable connections up to 8 simultaneous players/units
  • Supported left-handed play via the ability to flip the screen

There were other cool bits for the time it came out too, like a limited 32-bit math-coprocessor (used for some true 3-D polygon games like Hard Drivin’ and Steel Talons).  It wasn’t perfect; the system would slow down if you pushed it too hard (too many sprites, too many sampled sounds playing simultaneously), but it was creative and ambitious.

The Lynx started life as a hardware project by Epyx, initially called “Handy” (because it was to be the first handheld console).  Ex-Amigans RJ Mical and Dave Needle were involved in the design, which is why Handy feels like a tiny Amiga.  The initial specification was written in June of 1987 by Dave Needle.  Reading through it, two things are immediately evident:

  1. The designers of Handy had a passion for creating a fun device with as many progammer assists as possible
  2. Dave had a wry sense of humor

I will now reproduce for you some of the comedy gold hiding in the Handy specification.  I’ve truncated some sequences for brevity, but the words are all Dave’s:

The human input controls consist of a 4 switch (8 position) joy stick, two sets of 2 independent fire buttons, game pause button, 2 flablode buttons. power on, and power off….Flablode is a Jovian word meaning a device or function that we know is required or desired but for which we don’t have an actual definition (noun: flabloden, verb: to flablode).

3. Software Related Hardware Perniciousness
(or why some software people hate some hardware people)

There are certain things that the software ought not to do to the hardware. While these things are not physically destructive on their own, they will cause the hardware to act unpredictably strange, which may cause the user to be physically destructive. While we certainly could have protected the system from many of the following problems, I doubt that we would have found them all. In addition, the act of software doing one of these things means that there is a problem in the software anyway and the intended function would probably not happen. Additionally, this is only a toy. If this unit were a bio-medical device I would have found a safer solution.

3.1 Don’t Do These Things.

If you do any of the things that I tell you not to do, the hardware will act unpredictably and will not be expected to recover without a complete system initialization. So don’t do them.

3.1.5 Palettes and Page Breaks

This one is an actual hardware bug of mine…(much technical info removed)…Pen index numbers C,D,E, and F will be incorrectly unchanged. Sometimes I am such a jerk.

3.2 Please Don’t Do These Things.

There are also things that software people do that merely annoy the hardware people rather than annoy the end user. This includes seemingly harmless activities like sub-decoding bit values from byte descriptions (sprite types, for instance), or assuming address continuity between areas of hardware…Please don’t do them. It would be difficult to list all of the possibilities, so I will list the general considerations and ask you to be sensible about them. In addition, please feel free to submit a request for an exemption-on a specific case. If it is granted, we will change the specification so as to make the special case forever legal. The price will be small.

3.3 Do It This Way

Some of the hardware functions, as designed by us mindless brutes, require special handling. As we discover these requirements, I will list them here.

4.3 CPU Sleep

BIG NOTE: Sleep is broken in Mikey. The CPU will NOT remain asleep unless Suzy is using the bus. There is no point in putting the CPU to sleep unless you expect Suzy to take the bus. We will figure out how to save power some other way.

All hardware collision detection is done with the data in the collision buffer, not the data in the video buffer. This has obvious advantages and will be explained at seminars and in newsletters forever….In addition, the software can either do its own collision detection, or use the contents of the collision buffer for some weird collision detection algorithm. In either event, I will be mortally offended.

In addition, this means that when some of the bytes are not reloaded, the length of the SCB will be smaller by the number of bytes not used. If I have said this in a confusing manner, then I have.

Well, I finally found the bug that required a pad byte of 0 at the end of each scan line of data. But, It is actually 2 bugs. I have fixed one of them, but the other requires an extensive change. Too bad, I am out of time. Therefore: There is a bug in the hardware that requires that the last meaningful bit of the data packet at the end of a scan line does not occur in the last bit of a byte (bit 0). This means that the data packet creation process must check for this case, and if found, must pad this data packet with a byte of all Os. Don’t forget to adjust the offset to include this pad byte. Since this will only happen in 1/8 of the scan lines, it is not enough overhead to force me to try to fix the bug. Sorry.

This bit can be used to pause the sprite engine. The ‘unsafe’ condition of the internal registers is not directly affected by this bit.

I need to think about how to use it.

Receive parity error can not be disabled. If you don’t want it, don’t read it….We have just discovered that the calculation for parity includes the parity bit itself. Most of us don’t like that, but it is too late to change it.

11.7 Unusual Interrupt Condition

Well, we did screw something up after all. Both the transmit and receive interrupts are ‘level’ sensitive, rather than ‘edge’ sensitive. This means that an interrupt will be continuously generated as long as it is enabled and its UART buffer is ready. As a result, the software must disable the interrupt prior to clearing it. Sorry.

11.8 left out

I left something out. I know what it is but by the next time I revise this spec, I may have forgotten.

I have forgotten.

12.1.4 Bugs in Mathland

BIG NOTE: There are several bugs in the multiply and divide hardware. Lets hope that we do not get a chance to fix them.
1. In signed multiply, the hardware thinks that 8000 is a positive number.
2. In divide, the remainder will have 2 possible errors, depending on its actual value. No point in explaining the errors here, just don’t use it. Thank You VTI.

12.4 Qbert Root

As a compromise between the square root and qube root desires of the software people, and the schedule desires of the management, we have decided to incorporate the function of QbertRoot. The required steps are:
1. Start a 16 by 16 multiply.
2. Immediately write to ‘E’ which will try to start a divide.
3. Read the result from “D,C,B,A’.

(editor’s note:  I can’t tell if QbertRoot is an actual function, or trolling.)

16. Known Variances From Anticipated Optimums
This is a list of the known bugs in the hardware.

…It will be OK to write to the twentyfour 16 bit registers of the Suzy SCB PROVIDING that you only do it via the MACRO PROVIDED TO YOU BY RJ MICAL. In addition, you must understand that the contents of this macro may change if future revisions of the hardware so require. In addition, you must understand that future hardware may make the process not work and therefore the macro will be changed to be a warning that you can’t use it anymore.

Don’t cheat.

My personal favorite, saved for last:

7.3 Stereo

The 4 audio channels can be individually enabled into either of the two output drivers. This is not now in the hardware. It may never get into the hardware. After all, I hate music. However, since I acknowledge that I am wrong about some kinds of music (in the right circumstances, with me not present) I have graciously allocated one entire byte for the possible implementation of another useless and annoying sound feature.

(For the record, that feature did go into the hardware, in the second hardware revision of the Lynx.  If you have the later hardware, some audio is in true stereo.)

If all hardware/technical documentation was written this way, I’d be an embedded systems programmer by now.

I’ve scanned and OCR’d the full Handy specification for anyone wanting to learn more about the Lynx.  There’s a compo-winning demo hidden in the hardware, just waiting to be found.


One Response to “Comedy gold in the Handy specification”

  1. […] Comedy gold in the Handy specification – Posted by Trixter on August 12, 2015 The Atari Lynx is my favorite handheld console. Planning and design started in 1986, long before the Nintendo Game Boy, but… […]

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