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Cromemco dazzler replica project

Gary C

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Just found something !

The North star 16K & 32K Dynamic RAM board instructions includes specific modifications to allow the Dazzler to work with it and the Z80. So I should be able to get it to work in a N*

Which is nice.

This is from the 16K board manual, the 32K instructions has something similar

Modifications

SPECIAL DMA APPLICATIONS
This section describes modifications for the RAM-16-A which may be necessary for use with such DMA devices as the Cromemco DAZZLERTM. These modifications are only needed if the RAM-16-A is being used with a Z80 or Z80A processor board. (To use the RAM-16-A with a special DMA device in an 8080-based system, it is necessary only to install a resistor as described in step D1 below.)

D1. If the DMA device is simulating an 8080 memory cycle, D07 must be true during PSYNC. If the device does not drive D07, a pull-up resistor (say, 1K) to Vcc will suffice. A logical place to add this resistor would be at the DMA controller.
D2. Install resistor R12 (220 ohm, red-red-brn) at location 5E and capacitor C10 (33pF dipped mica) at location 5E. This RC circuit acts as a delay for the CC-DBSL/ signal.
D3. Add an unused inverter to the circuit by connecting a jumper wire between the location labeled PHLDA (location 7E) to 2C pin 11 and another jumper wire from 2C pin 10 to 2D pin 12. Now cut the trace from 2C pin 12 to 2C pin 10.
D4. Add a second inverter to the circuit by connecting a jumper wire from the location labeled CC-DSBL/ (location 4E) to 7C Pins 4 and 5 and another jumper wire from 7C pin 6 to 7D pin
1. Also, cut the trace on the solder side of the PC board between 7D pin 1 and 7C pin 7. This allows memory cycles to start on the condition: PSYNC AND PHI 1 AND CC-DSBL/
D5. On the header at location 7D, be sure the jumper from pin 1 to pin 2 is installed, as it should be for Z80 operation.
 
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Hugo Holden

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Additional to what Hugo said...

A basic no-frills static RAM board (which includes most of the early static RAM boards including the ones specifically mentioned by Hugo) will work in most cases. The board does not need to be exceptionally fast - if it is able to run with no wait states in an Altair 8080, it will be fast enough.

The problem with using dynamic RAM and a board that uses DMA like the Dazzler is:
- if a dynamic RAM board is busy doing a refresh cycle, the requesting bus master will need to wait before it can complete a memory read or write. The Dazzler board has no ability to wait for a RAM board that is not immediately ready for a data read cycle.
- many dynamic RAM boards are dependent on the ability to "steal" machine states when the bus is not being accessed - these occur frequently when a CPU board is the only device accessing RAM. The Dazzler board is accessing RAM on a constant regular basis, which may not allow the RAM board to "steal" a sufficient number of machine states to allow the RAM board time to perform its required frequency of refresh cycles.
+1

and the other thing I could say about S-100 memory cards, I have repaired a lot of them now. The Seattle static ram cards are super reliable. They have very good quality dual wipe IC sockets. With these cards (I have a few) the only thing I could find wrong was the very occasionally defective Ram IC.

On the other hand, most of the early Processor Technology 16kRa DRAM cards have multiple faults. These include multiple poor IC socket claws (they used the horrible TI sockets). Failures in the Delay line modules (the coils in those go O/C secondary to residual flux related corrosion, but I created a modern substitute module). So to get a 16kRA card working reliably requires every IC socket claw cleaned and checked one by one for tension. All the IC pin sides on their narrow edges immaculately clean and finished with 1000 grade paper to remove the oxides & lubricated.That is at least 4 hrs work. Possibly a new delay line module and replacing the occasional defective DRAM IC and of course the CTS switches. Then you will have a card that won't conk out on you every other day.

So if I was asked the question, Which is the better 16k memory card for any S-100 computer, I would say the 16k standard static ram card from Seattle computers, regardless if you intend to use a Dazzler, or not..
 

Hugo Holden

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This looks like a good 32k static ram board.


and another one from the same seller :



and a 64k static RAM :


 
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Gary C

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Received the boards and while they are the cheapest they look OK.

Still need verifying and probably aren't perfect.

Does anyone want a pair to help check them over and maybe build them ?

Remember, not verified yet and may contain errors.
 

wperko

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Out of curiosity, do you have any software that runs in the 4x resolution B&W mode? I'm wondering what the 128x128 pixel mode looks like. (Did anything actually use it?) Mainly I'm wondering about both modes... is the active video field 256 lines out of the possible 262 in height? I imagine a fair bit of it must get cut off in the overscan on a typical CRT, which leaves me wondering what the "effective" on-screen pixel resolution is. In color 64x64 mode are the color pixels three pixels tall (192 lines) or four (256)? I assume it must double-scan the 128x128 in the 4x mode... or is that rendered as just a "letterboxed" strip?

Since you mentioned the Matrox ALT-256... is there much software out there for that? I was kind of wondering if I might be able to emulate it without too much trouble with the video processor idea I've been working on. According to the manual it works by setting individual pixels by receiving X/Y/on-off coordinates via I/O ports, there's no "direct memory access"? Is there any delay in this process with the card, or can the CPU ram pixels in at full speed with no wait states?

Hi,

I have a ton ... almost all the software written for the DAZZLER and I even have .PDFs of most (if not all) of the documentation that still exists. It took a long time to track it all down and get it into one place ... my PC and when I get a working DAZZLER on my website: http://www.brainless.org/Altair/Repository.html Search "DAZZLER" ...

.
 

wperko

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Are you going to try some of Gary's pcb's that he offered on post #164 ? You could build them and help Gary verify them by testing with your extensive software collection.

Hi,

What is the link to Post #164? I'd be happy to build a board and test the software I have (3FDDs worth) ...
 
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Searching for Dazzler replica projects, I found this thread which is now more than one year old.

I recently was happy to acquire a High Resolution Graphics board from Vector Graphic, which probably has been Vector Graphic's response on Cromemco's Dazzler. It has similar features (bi-level and nibble greyscale modes with double the Dazzler resolution and dedicated frame buffer memory, but lacks the color mode). Now I am curious whether in the meantime there are any updates on this thread's topic, since I am seriously planning a Dazzler replica build based on the work done by Hugo and Gary.

-Ansgar
 

daver2

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Welcome to VCFED (as this is your first post).

I suppose the question is "why recreate the wheel when Hugo has already done it"?

Dave
 

Gary C

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Searching for Dazzler replica projects, I found this thread which is now more than one year old.

I recently was happy to acquire a High Resolution Graphics board from Vector Graphic, which probably has been Vector Graphic's response on Cromemco's Dazzler. It has similar features (bi-level and nibble greyscale modes with double the Dazzler resolution and dedicated frame buffer memory, but lacks the color mode). Now I am curious whether in the meantime there are any updates on this thread's topic, since I am seriously planning a Dazzler replica build based on the work done by Hugo and Gary.

-Ansgar
Hi

The problem I think with Hugo's board is that the company now own the Gerbers.

I did get some boards made from the Gerbers I produced, but I have never got around to populating them. If anyone wants them I can email them.

I can send you a pair if you PM me an address (and if its not daft money to post)
 

VERAULT

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Hi

The problem I think with Hugo's board is that the company now own the Gerbers.

I did get some boards made from the Gerbers I produced, but I have never got around to populating them. If anyone wants them I can email them.

I can send you a pair if you PM me an address (and if its not daft money to post)
Thats why I didnt buy one of hugos boards as the price the company is quoting. I applaud his efforts of course but the fact they retain the gerbers is prohibitive. Anyway Gary, I am interested in a board.
 

Gary C

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I can Email Gerbers if thats easier. As they are JCL ones, it might even be cheaper.

MUST ADD

They have not been tested or verified and I can't and wont guarantee that they can't cause damage.
 

Hugo Holden

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Thats why I didnt buy one of hugos boards as the price the company is quoting. I applaud his efforts of course but the fact they retain the gerbers is prohibitive. Anyway Gary, I am interested in a board.
They are expensive alright, but they were all Gold plated everywhere, that increased the costs and it adds up because it is a board pair. Remind me how much they quoted, I think I have some left over that I could sell for a reduced cost.
 

VERAULT

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They are expensive alright, but they were all Gold plated everywhere, that increased the costs and it adds up because it is a board pair. Remind me how much they quoted, I think I have some left over that I could sell for a reduced cost.
Oh you put me on the spot. I dont recall the exact figure but it was enough to make me say, "I cant throw that down for my hobby."
 

Hugo Holden

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Oh you put me on the spot. I dont recall the exact figure but it was enough to make me say, "I cant throw that down for my hobby."
But also, you have to take the exchange rate into account when you see the $ quote, if something is say $300 AU, that is only about $196 US.
 

VERAULT

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Yes I am aware. I buy plenty of item from overseas. But it was prohibitive... for my budget maybe not to others with more disposable income.
 
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