Video for KIM?

[kakemoms]

My KIM-1 has just arrived and I am already thinking of how it could have been "improved". I am aware of the S100 bus converter/externders out there, and there is probably something you can plug into that... but it would be more interesting to have some contemporary video chip hooked up through a small board.

Anyone knows of such design/schematics somewere?

[fachat]

I have a book, called "the cheap video cookbook" that seems to use the CPU operations to trigger reads from memory and output them, and it says it supports the KIM-1 (first edition, second printing from 1979).

I've read only (edit: 1/10h, not 1/4th) of it yet, so no details to share, but maybe there is an online copy available somewhere?

[Sean]

fachat wrote:

I have a book, called "the cheap video cookbook" that seems to use the CPU operations to trigger reads from memory and output them, and it says it supports the KIM-1 (first edition, second printing from 1979).

I've read only (edit: 1/10h, not 1/4th) of it yet, so no details to share, but maybe there is an online copy available somewhere?

The author of that book, Don Lancaster, has electronic copies of that, and much more, on his website.

https://www.tinaja.com/ebksamp1.shtml

[Dr Jefyll]

Quote:

The author of that book, Don Lancaster, has electronic copies of that, and much more, on his website.

Yes -- he's quite a guy, and it's quite a site!

I wrote about Cheap Video on this page of my own site, but here's a summary based on my own experience.

I've implemented Cheap Video three times (including on my Franken-KIM). No two of those implementations were alike, and none of them was quite like Lancaster's. But they all used Lancaster's idea of tricking the CPU's PC register into behaving as a counter for generating memory addresses.

The KIM-1 is a good candidate because it already has tristate buffers which separate the memory data bus and the CPU data bus. Ordinarily these two buses would carry the same data, but during a Cheap Video horizontal scan line the tristate buffer is inhibited, and the CPU doesn't see what's really in memory. Instead, the CPU gets repeatedly fed a dummy instruction such as CMP #$C9 -- a 2-byte instruction which also consumes 2 cycles. This causes the PC register to behave like a counter. (The final dummy instruction is an RTS, and that's what breaks the spell and takes us back into reality.)

Meanwhile during the scan line, memory simply fetches bytes from the addresses supplied by the "counter" and these bytes appear on the memory data bus (but not the CPU data bus).

On a small system (KIM-1) you'll probably feed the memory bytes to a Character Generator ROM whose output in turn feeds the video shift register. But for a bit-mapped display the bytes from memory go straight into the video shift register (ie, there is no CG ROM).

During the Hor-retrace interval the CPU executes some "real" code (albeit very timing sensitive) which sets up the next scan line. Then a JSR occurs, and (in Lancaster's version) it is the new address (ie, that of the video buffer) which causes an address decoder to turn off the tristate buffer and feed the CPU CMP #$C9 instead of what's really in the buffer. Hope that helps!

-- Jeff

ps - Back in the day, Lancaster relied fairly heavily on 32-byte TTL PROM's. Nowadays it's reasonable to use a much, much large EPROM (wasting most of its capacity), or use a PLD to create a 32-byte ROM equivalent.

[Sean]

kakemoms wrote:

My KIM-1 has just arrived and I am already thinking of how it could have been "improved". I am aware of the S100 bus converter/externders out there, and there is probably something you can plug into that... but it would be more interesting to have some contemporary video chip hooked up through a small board.

Anyone knows of such design/schematics somewere?

Aside from the cheap video techniques, a common approach for more modern video is interfacing with one of the TFT LCD controller chips like the RA8875, SSD1963, BT815, etc. and tacking a resistor network or DAC onto the end to produce VGA output, or feed it to a DVI encoder to produce VGA output. These chips typically support SPI and/or can act as a memory-mapped I/O device.

Adafruit has an Arduino shield for $34.95 using the RA8875; you'd have to do your own conversion to VGA or DVI from there. https://www.adafruit.com/product/1590
The Gameduino 3X Dazzler uses a BT815 feeding a FPGA that upscales and outputs HDMI. https://www.crowdsupply.com/excamera/ga ... 3x-dazzler

Or buy the chips from Mouser or eBay or wherever and build your own.

There's a bunch of projects and products out there utilizing microcontrollers, or (perhaps cheapest) the Raspberry Pi Zero.

And FPGA and CPLD solutions, of course. The VGATonic is an SPI-driven CPLD-based approach, for example. https://github.com/dqydj/VGAtonic

[BigEd]

This search turns up a few threads on displays, including Displays for retro-computing - what you do use?

[kakemoms]

I like the concept of Cheap Video with the CPU and only a few extra ICs. Its a simple addition and hopefully not too much that can fail...

Hmm.. maybe I should get a modern KIM-1 reproduction to test it on first, just in case..

I also got a few books with my KIM-1. There are three original MOS manuals from 1976 and a book "The First Book of KIM" by ORB. Its similar to the same book in the "Books" section, but a simpler "typewriter" layout.

[Dr Jefyll]

kakemoms wrote:

Hmm.. maybe I should get a modern KIM-1 reproduction to test it on first, just in case..

Not sure I understand. Are you worried about making an incorrect mod -- one you're unable to reverse?

Also, be aware that a modern KIM-1 reproduction might be harder to work with. For starters, it'll likely be a lot smaller, compared to KIM-1's generous proportions. Also, as noted earlier, the actual KIM-1 features tri-state buffers (74xx125) between the CPU data bus and the DataOut pins of the 2102 RAM array. Cheap Video requires the tri-state buffers, but they're probably absent on a modern KIM-1 reproduction -- you'd have to add a buffer yourself. (A 74xx245 would do the trick.)

Quote:

There are three original MOS manuals from 1976

Pure treasure! I talk about those manuals in this post. And there's an entertaining story about the author, Chuck Peddle -- his goals for the manuals, and his procrastination!

-- Jeff

[kakemoms]

Dr Jefyll wrote:

kakemoms wrote:

Hmm.. maybe I should get a modern KIM-1 reproduction to test it on first, just in case..

Not sure I understand. Are you worried about making an incorrect mod -- one you're unable to reverse?

Also, be aware that a modern KIM-1 reproduction might be harder to work with. For starters, it'll likely be a lot smaller, compared to KIM-1's generous proportions. Also, as noted earlier, the actual KIM-1 features tri-state buffers (74xx125) between the CPU data bus and the DataOut pins of the 2102 RAM array. Cheap Video requires the tri-state buffers, but they're probably absent on a modern KIM-1 reproduction -- you'd have to add a buffer yourself. (A 74xx245 would do the trick.)

Quote:

There are three original MOS manuals from 1976

Pure treasure! I talk about those manuals in this post. And there's an entertaining story about the author, Chuck Peddle -- his goals for the manuals, and his procrastination!

-- Jeff

I certainly won't do anything to the KIM-1. Modifying an original 45-year old computer is not even up to consideration. The video solution will have to be a plugin, but its a risk to do so as well. That is why a reproduction board was considered. There are a few on ebay, but as you point out, they seems to be CMOS.

Well, maybe I will make one myself once I finish my Apple-1 reproduction. Its expensive to source components, and the 6530's are hard to find. A 6532-based solution is probably ok...

[ThePhysicist]

If you have not seen it, there is a guy offering complete Apple 1 kits on ebay for 300$.

[plasmo]

kakemoms wrote:

I certainly won't do anything to the KIM-1. Modifying an original 45-year old computer is not even up to consideration. The video solution will have to be a plugin, but its a risk to do so as well.

Is the 6502 socket on KIM-1 screw machine socket? I'm wondering whether a VGA daughter board can be plugged into the 6502 socket to provide text-based (64 columns x 48 lines) VGA display.
Bill

[BillO]

plasmo wrote:

Is the 6502 socket on KIM-1 screw machine socket? I'm wondering whether a VGA daughter board can be plugged into the 6502 socket to provide text-based (64 columns x 48 lines) VGA display.
Bill

On my KIM-1 the 6502 was soldered in.

[kakemoms]

All components on my KIM-1 are soldered to the board. Its a pre-Commodore version. An option could be a DIP test clip. If I can find a large one...

As for the comments concerning Apple-1, I have a Newton NTI board that was made according to the same process used in 1976. All the sockets are Texas Instruments sockets of the correct type, and all passives are age-correct. IC’s are also with 1976 date codes and I even bought a Data I/O series 22 to burn MMI proms of the correct type (but unfortunately with 1980 date codes as I have only found one 1977 and no 1976). Total cost has been around $6000 at this point.

If I get fortunate in the future, I would consider buying a real Apple 1, but at the moment I have to focus on my wife and kids.

[BillO]

kakemoms wrote:

If I get fortunate in the future, I would consider buying a real Apple 1, but at the moment I have to focus on my wife and kids.

In the mid-80's a friend of mine showed me 2 kiosks the company he worked for had made as prototypes back in the late 70's. They were supposed to be information kiosks for trade shows, but they had decided not to go ahead with them because the technology was charging so rapidly that by the time they had got them going, they were considered out of date. They were powered by Apple-1 boards. He told me they were going to scrap them and asked me if I wanted them. I said something to the effect of "They're just junk, go ahead and trash them."

I think of that from time to time...