Search found 658 matches

by Peter
Thu Aug 16, 2018 9:02 pm
Forum: Hardware
Topic: 8301
Replies: 66
Views: 2451

Re: 8301

Eh, yes - the thing is, we re limited to A16, A17 for decoding and that means 256k total which implies a cut-down version of SMSQ/E :( I didn't mean that SMSQ/E must fit into a 8301 replacement - it would require a RAM extension anyway and could be loaded from mass storage under QDOS/Minerva. But a...
by Peter
Thu Aug 16, 2018 9:16 am
Forum: Hardware
Topic: 8301
Replies: 66
Views: 2451

Re: 8301

A long time ago i read the reason for this is that /RAS cycling is used to drive an internal charge pump which generates a negative substrate voltage for the RAM chip, which is not visible on the outside. I have seen a maximum /RAS high time only for similar DRAM chips yet, not the 4164 in particul...
by Peter
Tue Aug 14, 2018 9:05 am
Forum: Hardware
Topic: Connecting a mouse to the QL
Replies: 5
Views: 266

Re: Connecting a mouse to the QL

RWAP wrote:A quick look on ebay shows some ps/2 mouse to serial port adaptors.

The adaptors I saw are passive and only work with obsolete combo mice which are also serial internally. No solution for recent PS/2 mice.
by Peter
Mon Aug 13, 2018 11:14 am
Forum: Hardware
Topic: 8301
Replies: 66
Views: 2451

Re: 8301

Have also a look at the maximum period required for /RAS. It does have a maximum (as long as it is) so it cannot be completely static. But I am sure at that rate the current consumption would be FAR lower. Not sure what you mean - /RAS pulse width seems irrelevant, /RAS would never be active. Do yo...
by Peter
Fri Aug 10, 2018 9:52 am
Forum: Hardware
Topic: 8301
Replies: 66
Views: 2451

Re: 8301

DB0..DB7 - input - RAM (and in most cases 8302) data bus, connects to the CPU data bus using a 74LS245 bus buffer. In case of a "modern" FPGA 8301 replacement with sufficient RAM, I would make DB0..DB7 bidirectional, not input. Keeping /RAS, /CAS0, /CAS1 and /WE inactive should be suffici...
by Peter
Wed Aug 08, 2018 1:00 pm
Forum: Hardware
Topic: 8301
Replies: 66
Views: 2451

Re: 8301

The one thing I would make optional are microdrives, though. While the rest sounds good, I'm a bit sceptical to remove microdrive support. The demand will mainly come from people who want the possibility of full "retro" usage. Even I keep at least one microdrive intact in my original QLs,...
by Peter
Wed Aug 08, 2018 10:11 am
Forum: Hardware
Topic: 8301
Replies: 66
Views: 2451

Re: 8301

My gripe with the motherboard would be components that are problematic to replace or remove when they fail (in this case it would be RAM), and signal integrity. After all I just re-used the 8302 and IPC on the Aurora :P Yes, a QL motherboard replacement for obsolecence, signal quality and repair re...
by Peter
Tue Aug 07, 2018 12:00 pm
Forum: Hardware
Topic: 8301
Replies: 66
Views: 2451

Re: 8301

I‘d like a minimal replacement that doesn‘t do more than the original ZX8301 except outputting the screen as VGA 1024x512 with pixel doubling and line trippling, for example. Most likely you mean 1024x768... and yes I would also just like a minimal replacement, so there is a decent video signal. As...
by Peter
Mon Aug 06, 2018 1:37 pm
Forum: Hardware
Topic: 8301
Replies: 66
Views: 2451

Re: 8301

For sure - although you then still have a big heap of inactive hardware that never the less consumes power and influences signal integrity. But that is a story for a later post. Don't you think that keeping RAS and CAS quiet would have a great impact? (No need to answer seperately if that's part of...
by Peter
Mon Aug 06, 2018 1:27 pm
Forum: Hardware
Topic: 8301
Replies: 66
Views: 2451

Re: 8301

I was looking into the idea of using on board RAM in an FPGA, but even with the basic QL display resolution, the amount of block ram you need means using quite a large FPGA in relative terms. The lowest end Lattice ECP5 family member for 4,25 € (at quantity 1) has already 64 KB block RAM. Not as co...

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