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Why the Apple II Didn’t Support Lowercase Letters

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Re: Why the Apple II Didn’t Support Lowercase Letters

#91

Post by ddingus »

thought_alarm wrote: post #89
joezydeco wrote: post #75

Earlier quoted context omitted.

Or, perhaps, he didn't want to pay for a video generator IC like a 9918 or 6845. If you look at the video generation circuit on an Apple ][ it's all done in real-time in TTL, alongside the DRAM refresh activity . And it's all crammed into the normally unused tock of the 6502, making this work with virtually zero overhead on the CPU. That's the reason why the memory mapping of the screen isn't linear to the physical d…

Right, but the Apple II video generator is already reading 40 bytes per scan line, and is using all 8 bits of each byte to generate the video signal. I would think that drawing 8 pixels per byte instead of 7 would have been the simpler thing to implement.

Actually, it's not.

In the Apple 1, only 7 bits were output. Expanding that circuit to do graphics would take a byte and still output just 7 bits, simple.

People are pretty sure the Apple 1 video circuit was just expanded to do graphics, which is why it's 7, and that left the high bit for a color shift.

Re: Why the Apple II Didn’t Support Lowercase Letters

#92

Post by ddingus »

exsf0859 wrote: post #88
thought_alarm wrote: post #64

Earlier quoted context omitted.

The Atari 400/800 and the TMS9918 (TI 99/4A, Colecovision, etc.) are 320 pixels wide and were designed to run on those same 1970s home television sets, and they didn't have an overscan problem (maybe some sets did, but most didn't). I don't think the Apple II had to cut the screen width down to 280 pixels. That's the heart of the question. Did Woz think that 320 pixels would not fit, or did he cut the width down for…

Err, as an Atari 400/800 owner, I can assure you that they did in fact have an overscan problem. Atari BASIC even defaulted to not printing to the first 2 characters and last 2 characters of each line. Here's an example Atari BASIC program that uses POKE statements to change and then restore the default margins. https://www.atariarchives.org/c2bag/page003.php

Those margins make almost exactly the Apple display region active text.

Interesting! I never noted that before.

Re: Why the Apple II Didn’t Support Lowercase Letters

#93

Post by mzs »

thought_alarm wrote: post #78
mzs wrote: post #56

Earlier quoted context omitted.

The 8th bit was never ignored, it was for phase, and for example determined if you saw green or orange. Probably the best ref for this is from '83, Gayler's "The Apple II Circuit Description." edit: corrected below, rev 0 non RFI (without the aux vid pin) ignored DL7

Actually, the very first Apple IIs only supported 4 colors in hi-res mode. The 8th bit was ignored. A later revision added support for 6 colors, using the 8th bit to shift the pixels and change the pallet.

Thank, I just consulted appendix B of my copy, you are correct. DL7 is unconnected in nonRFI rev0 though every later Apple II RFI or not could do 6 color HIRES.

Re: Why the Apple II Didn’t Support Lowercase Letters

#94

Post by ddingus »

dhosek wrote: post #85

Reading Woz's talking about hand-assembling his 6502 code reminded me of my own practice which was the same. I would write out programs on graph paper with columns for the physical address, any labels and space for what the code would assemble to to the left of my actual assembler code. I would drop down to the monitor to hand-enter the hex code I would hand-generate. When you're working under constraints like this,…

Same here.

Early on, I didn't have a machine of my own and would hand assemble programs to be typed in next time I could get some machine time.

Re: Why the Apple II Didn’t Support Lowercase Letters

#95

Post by thought_alarm »

ddingus wrote: post #81
joezydeco wrote: post #75

Earlier quoted context omitted.

Or, perhaps, he didn't want to pay for a video generator IC like a 9918 or 6845. If you look at the video generation circuit on an Apple ][ it's all done in real-time in TTL, alongside the DRAM refresh activity . And it's all crammed into the normally unused tock of the 6502, making this work with virtually zero overhead on the CPU. That's the reason why the memory mapping of the screen isn't linear to the physical d…

And it made add on cards simpler, as well as cycle counting. In addition, the overall throughput of the CPU is better than most other machines, giving the Apple an effectively higher speed at that clock rate. Overall, given memory expansion, the goofy screen didn't end up being too big of a deal. Most programmers made Y axis lookup tables and called it a day. The fact that the artifact color mapping repeated every wo…

Speaking of add on cards, I own a TMS9918 video card for my Apple II. It's remarkably simple. The 9918 manages its own 16 kB of VRAM and it doesn't place any timing restriction on the host system.

You'd think that the 9918 would be a bottle neck between the CPU and the VRAM, but the Apple II can write to the 9918 VRAM as fast as its own internal RAM. Faster, actually, since the destination address auto-increments. That was a surprise.

Re: Why the Apple II Didn’t Support Lowercase Letters

#96

Post by Stierlitz »

spiritplumber wrote: post #69
spzb wrote: post #17

Site down at the moment. Mirror : https://web.archive.org/web/20200910152535/http://www.vintag...

back then we used to call it slashdotting, what do we call it now?

> back then we used to call it slashdotting, what do we call it now?

That was back when slashdot was a real tech site.

Re: Why the Apple II Didn’t Support Lowercase Letters

#97

Post by ddingus »

thought_alarm wrote: post #95
ddingus wrote: post #81

Earlier quoted context omitted.

And it made add on cards simpler, as well as cycle counting. In addition, the overall throughput of the CPU is better than most other machines, giving the Apple an effectively higher speed at that clock rate. Overall, given memory expansion, the goofy screen didn't end up being too big of a deal. Most programmers made Y axis lookup tables and called it a day. The fact that the artifact color mapping repeated every wo…

Speaking of add on cards, I own a TMS9918 video card for my Apple II. It's remarkably simple. The 9918 manages its own 16 kB of VRAM and it doesn't place any timing restriction on the host system. You'd think that the 9918 would be a bottle neck between the CPU and the VRAM, but the Apple II can write to the 9918 VRAM as fast as its own internal RAM. Faster, actually, since the destination address auto-increments. Th…

Interesting!

Hmmm, is the bitmap linear by line, or C64 style?

Auto increment + C64 style would rock pretty hard. It's still good per line.

Both have their merits.

Re: Why the Apple II Didn’t Support Lowercase Letters

#98

Post by jecel »

thought_alarm wrote: post #34
tlb wrote: post #21

Earlier quoted context omitted.

For text, a 5x7 dot matrix font fits nicely in 7 (wide) x 8 (high). 8-pixel wide characters look funny: characters have to be an odd number of pixels to get symmetrical letters like A, so you either have 1 or 3 pixels spacing between. While NTSC allows 320 pixels, typical analog TVs overscanned a lot and you'd miss the right and left column or 2 of text.

That seems like a big price to pay for slightly better text spacing. Virtually every other home computer used 6 or 8 pixels per char/byte. I don't think overscan would be an issue. The TMS9918 is also (the equivalent of) 320 pixels wide, and it was used in many different home computers and game consoles intended to connect to the family TV. There's no overscan issue, unless it's connected to an Apple II monitor. When…

Actually, the TMS9918 has a 240x192 text mode with 40x24 characters of 6x8 each and several 256x192 graphics modes with 32x24 characters of 8x8 each. This is always fewer than Apple II's 280 pixels per line.

Re: Why the Apple II Didn’t Support Lowercase Letters

#99

Post by supernova87a »

spiritplumber wrote: post #69
spzb wrote: post #17

Site down at the moment. Mirror : https://web.archive.org/web/20200910152535/http://www.vintag...

back then we used to call it slashdotting, what do we call it now?

Whatever happened to Slashdot? Did the slowness of new stories appearing + their comments system turn people off eventually, compared to interfaces like here?

I used to read them daily.

Re: Why the Apple II Didn’t Support Lowercase Letters

#100

Post by kevin_thibedeau »

supernova87a wrote: post #99
spiritplumber wrote: post #69

Earlier quoted context omitted.

back then we used to call it slashdotting, what do we call it now?

Whatever happened to Slashdot? Did the slowness of new stories appearing + their comments system turn people off eventually, compared to interfaces like here? I used to read them daily.

10 years ago I scraped a representative slice of all /. postings from the fall of every year. It was apparent that the rate of new UIDs was falling and that the bulk of the posting was done by a limited and shrinking cohort in the range of 100K to 400K. Mobile boosted the prevalence of AC posts but that didn't compensate for the drop off. I ran a regression out and predicted they'd be dead by 2023. Looks like they're on track.
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