Recent content by hmb

You mean like this "virtual sector generator" for 5.25" floppy drives ? https://deramp.com/vsg.html

For proper operation, the old school QumeTrak 842 does require a "TG43" input signal. In the Qume manual the "TG43" signal is actually referred to as the "Low Current" input signal. Older drives like the QumeTrak 842 lacked the "smarts" built into later model 8" drives that kept count internally...

While the joystick mechanism used by the Cromemco controller is mechanically similar to that found in Kraft's RC transmitters, I wonder whether the resistance range of the potentiometers used for these two applications was identical. I have not been able to find any specs for the resistance...

86-DOS would work with a very basic serial terminal. When used with a VT-52, its function keys could be used to perform several very basic line-editing commands as described in the 86-DOS user manual.

The system console was a serial terminal connected to the serial port on the SCP-300 "CPU Support Card".

The only way to find out for sure is to test it so that you can verify this claim by the manufacturer was correct. Your Delta Products DRAM board, and a couple of other DRAM boards also advertised as "Dazzler compatible" were manufactured in the same era as the Dazzler and likely (as a selling...

Each of these two external drive systems required a specific H89 interface board. Needless to say these interface boards (like the Z-47 and Z-67 themselves) are scarce and would be hard to find. If you are looking for a mass storage device for your H89, consider a "modern" design using a CF...

Few H8 (or H89) systems were equipped with 8" floppy drives. The "official" Heathkit 8" drive product for the H8 was the H-47, a very expensive combination of a rather simple interface card (installed in the H8) and a peripheral unit containing the 8" drive itself along with all the logic...

No question - the CompuPro RAM17. It's design (like the SCP 16K board) uses the least number of parts, and S100 signals, required for an S100RAM board to work. Both the RAM17 and SCP 16K board currently sell for a similar price on the used market. However the advantage clearly goes to the RAM17...

In Holden's discussion of the Dazzler, he mentioned having successfully tested it with the "Seattle Computer" 16K RAM board, and the CompuPro RAM17 board (which is what I use). Incidentally Mike Douglas had a batch of RAM17 boards he was selling a month ago and may still have some available if...

The only board in your list that stands a chance of working with the Dazzler is the Vector Graphic 8K RAM - but I'd have to see the schematic to be sure, and I cannot find one for this board. None of the dynamic RAM boards you listed will work. The "mystery board" you pictured is also a dynamic...

As you pointed out for the Memory Merchant 65K16S board, the S100 address signals A0-A15 are latched by 74LS375s. The 74LS375 is a "transparent latch" as long as its control inputs are held high. However, if the control input goes from a high-to-low transition and then stays low, the output...

Correct. R1 is 270 ohms on both RevC and RevD boards. There is a typo in post 340 - the reference to "R1 should be 30K" should have said "R11 should be 30K".

I found an older (1980) version of the Cromix manual which only describes use of the 64KZ and no other RAM boards - which matches your experience.

I just quoted what the Z80 Cromix Admin Manual said. Perhaps it was a later version published after the original 64KZ had been discontinued, and Cromemco was just targeting "new owners" with their manual.