Search found 2477 matches

by Dave
Tue May 26, 2020 5:49 pm
Forum: Hardware
Topic: Issue 6 VM12 & resistors confusion
Replies: 46
Views: 1395

Re: Issue 6 VM12 & resistors confusion

What did you see when you checked the power to the DRAm area? Was it nice and smooth, or dipping? What about at the 8302?

The inconsistency of this is similar to a QL I repaired many years ago where the DRAM wasn't refreshing properly, and it turned out to be a power/bounce problem.
by Dave
Mon May 25, 2020 7:27 pm
Forum: Hardware
Topic: Issue 6 VM12 & resistors confusion
Replies: 46
Views: 1395

Re: Issue 6 VM12 & resistors confusion

Are you using the EPROM directly? EPROM chip select is active low.
by Dave
Thu Apr 23, 2020 8:05 pm
Forum: Compatibles Corner
Topic: Q40/Q60 Roms
Replies: 18
Views: 732

Re: Q40/Q60 Roms

Would it be reasonable to do a flash adapter and IC to go there? Would it be in system programmable?
by Dave
Fri Apr 17, 2020 3:33 pm
Forum: Hardware
Topic: 5.25" floppy drive configuration
Replies: 27
Views: 1131

Re: 5.25" floppy drive configuration

What is the situation with termination resistors on the drives? If they're terminated incorrectly, they may accept "motor on" signals but not recognize data properly. On 5/25" drives, usually only the data lines were terminated on the last drive, with a resistor pack.
by Dave
Tue Mar 31, 2020 7:31 am
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1609

Re: QL Add-on ROM

You could have a physical witch to connect /WR. If you tie it to 5V it can’t be written. A mechanical pull-up.
by Dave
Mon Mar 30, 2020 6:44 pm
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1609

Re: QL Add-on ROM

May I propose thinking about this in a slightly different way? What if instead of a flash IC (20 year retention guarantee) you used a 128K low power SRAM and CR2032 battery as back-up power? In standby, the SRAM would retain contents using microAmps. The battery would last 15 or 20 years. If you spl...
by Dave
Sat Mar 28, 2020 10:13 pm
Forum: Hardware
Topic: QL-SD ROM
Replies: 15
Views: 804

Re: QL-SD ROM

Though I can't think of a use case where someone would use a QL-SD and want a Miracle hard drive.
by Dave
Sat Mar 28, 2020 7:32 pm
Forum: Hardware
Topic: QL-SD ROM
Replies: 15
Views: 804

Re: QL-SD ROM

It's not the first QL hardware to program its own flash, but it will be the first released hardware, yes.
by Dave
Sat Mar 28, 2020 4:14 pm
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1609

Re: QL Add-on ROM

I have programmed flash off the QL bus, during multi-tasking, without problems. If you recall my idea a few years ago of having multiple CPUs mapped through dual port SRAM to areas of the QL's memory map, I did a fair amount of work on it. I ended up using a small flash as a persistent system-progra...
by Dave
Fri Mar 27, 2020 4:05 am
Forum: General QL Chat
Topic: Comparing Sinclair QL to Commodore 64
Replies: 27
Views: 1087

Re: Comparing Sinclair QL to Commodore 64

If I had to pick a machine that was most line the QL, I would pick the Coleco Adam. Similarities: Both have two CPUs. The Adam 2nd CPU, used for system IO and memory management, is a 6801 - a small ROM microcontroller version of the 6800. In the QL, it's an 8049. Both communicate through an internal...