Search found 342 matches

by Nasta
Sat Apr 27, 2019 11:23 am
Forum: Hardware
Topic: ULTRA GOLD CARD
Replies: 24
Views: 2818

Re: ULTRA GOLD CARD

Seems like fitting the QL case is so important that even vaporware appears more gigantic than a machine that actually shipped. ;) I already noticed that in the old days... everything of importance needed to fit the QL case... And people were then tinkering to move their stuff outside the QL case, b...
by Nasta
Sat Apr 27, 2019 11:19 am
Forum: Software & Programming
Topic: How to reliably detect USER or SUPERVISOR mode across CPUs
Replies: 12
Views: 1190

Re: How to reliably detect USER or SUPERVISOR mode across CPUs

Dave wrote:How might detecting this tie in with detecting and enabling caches on the 68000, 68020, 68030 and 68060?


Enabling cache on a 68000 is REALLY hard.
by Nasta
Fri Apr 26, 2019 2:31 pm
Forum: Hardware
Topic: ULTRA GOLD CARD
Replies: 24
Views: 2818

Re: ULTRA GOLD CARD

That was actually the specification for a card which I was designing called GoldFire which was never finished for a variety of reasons I won't go into here. It also had a an option for an ethernet and audio controller chip, all derived from PC tech of the day. The reason for the name was that the de...
by Nasta
Tue Apr 16, 2019 7:24 pm
Forum: Hardware
Topic: Optimal Flatscreen monitors for QL and Q68
Replies: 24
Views: 2556

Re: Optimal Flatscreen monitors for QL and Q68

That's a rather complex discussion. The QL uses a 'fake progressive' timing close to the PAL spec with some liberties which never the less work fine on PAL compatible TVs and monitors. This format has 640 pixels per line, and 312 lines, which includes all invisible portions of the scan. Each line ta...
by Nasta
Tue Apr 16, 2019 6:18 pm
Forum: Hardware
Topic: WD1772 vs DP8473V
Replies: 8
Views: 1070

Re: WD1772 vs DP8473V

So far we can assume the old ULAs at $18000..$180FF and Qimi (original, not the one on the SQB) at $1BF00..$1BFFF. The rest is more or less up for grabs. One entry which I would add to this, is the entire first 4k of that area. There is a hidden agenda behind that one :P Curiosity raised :-) Someth...
by Nasta
Sat Apr 13, 2019 12:18 pm
Forum: Hardware
Topic: Issue 8 discussions...
Replies: 143
Views: 18561

Re: Issue 8 discussions...

It never has to contend for memory with the CPU as they are on separate and isolated buses, on either side of dual port RAM that allows both sides to access the same address simultaneously without conflict. This is the problem I meant. When the CPU is writing, while by chance the asynchronously clo...
by Nasta
Sat Apr 13, 2019 11:13 am
Forum: Hardware
Topic: Floating a thought to understand the issues...
Replies: 29
Views: 2668

Re: Floating a thought to understand the issues...

Some improvement in Interrupt handling can be done with the 'status affects vector' mechanism that z80 I/O and some of the 68K peripherals use. ...Little or no need to interrogate an ISR to find out what caused the interrupt. The down side is that almost all of the user vector space is clobbered by...
by Nasta
Thu Apr 11, 2019 3:12 pm
Forum: Hardware
Topic: Floating a thought to understand the issues...
Replies: 29
Views: 2668

Re: Floating a thought to understand the issues...

Let me backtrack here a bit, re 'blocking' and 'non-blocking' tasks. Once a second CPU is in the picture to handle IO, almost all tasks become 'non-blocking' in 'Dave-speak' :) The reason some things take over the entire machine are mostly historic. The underlying principle, though, is always presen...
by Nasta
Tue Apr 09, 2019 11:53 am
Forum: Hardware
Topic: Floating a thought to understand the issues...
Replies: 29
Views: 2668

Re: Floating a thought to understand the issues...

Well, that's a rather involved question :) Under QDOS the CPU is virtualized to each job (each sees it as completely available to itself to a very large extent), but memory is not in the strictest sense (that part is in a sense co-operative, as it relies on the CPU being able to address everything r...
by Nasta
Wed Apr 03, 2019 3:31 pm
Forum: Hardware
Topic: WD1772 vs DP8473V
Replies: 8
Views: 1070

Re: WD1772 vs DP8473V

In that 32K block, only 9 bytes seem to be actually used by memory mapped IO. A couple of mouse systems use three or four bytes near the top of that 32K. Part of the problem is that the area is only partially decoded so it contains aliases of those IO registers with the frequency dependent on wheth...