Search found 444 matches
- Mon Feb 14, 2022 4:11 pm
- Forum: Hardware
- Topic: Replacement for 68008
- Replies: 38
- Views: 7299
Re: Replacement for 68008
If the original ULA chipset is used, and the CPU is operated at higher speed, there has to be extra circuitry that will fairly faithfully emulate the original 68008 running at 7.5MHz. This is because the 8301 ULA makes certain assumptions about the signal timing on the 68008 in relation to the clock...
- Thu Jan 27, 2022 1:43 pm
- Forum: Hardware
- Topic: Dead SuperHermes - any hints/tips for investigation?
- Replies: 26
- Views: 4333
Re: Dead SuperHermes - any hints/tips for investigation?
If the EPROM code is available, it might be possible to 'refresh' the part but it will require skipping over the 'check blank' part as the part will not be blank. Usually some zero bits will revert to ones which is the un-programmed state. I think there was a flash version of the same PIC chip but h...
- Fri Dec 24, 2021 12:01 pm
- Forum: Hardware
- Topic: USB Keyboard IF
- Replies: 38
- Views: 8391
Re: USB Keyboard IF
It is an 8x8 matrix, thus 64 keys (mind the double shift keys!). However, shift, ctrl and alt are treated with extra diodes because there are some limitations to what keys can be pressed without 'phantom' keypresses being generated. Won't go into why here, suffice to say shift-ctrl-alt can be presse...
- Sun Nov 14, 2021 10:37 pm
- Forum: Hardware
- Topic: External QL microdrive?
- Replies: 17
- Views: 4502
Re: External QL microdrive?
An internal microdrive cannot be directly connected to the MDV connector because, unlike the external microdrive, most of the motor control components components are on the QL motherboard. Of course, it would be possible to re-create these circuits on an extra PCB which could then be connected to th...
- Wed Oct 27, 2021 9:21 pm
- Forum: Hardware
- Topic: Hermes status
- Replies: 87
- Views: 18086
Re: Hermes status
Here is a very interesting vendor from Poland that has several available batches of 8749 IPC chips. Ignore the first 4 which are one time programmable used, hence already programmed and not erasable. https://www.ebay.de/str/tvsatelectronic/IC-Microcontroller/_i.html?_storecat=18701871014&_sop=2&...
- Wed Sep 29, 2021 6:45 pm
- Forum: Hardware
- Topic: PIC for 8049
- Replies: 13
- Views: 3418
Re: PIC for 8049
you could combine the functions of both chips into something larger - but then it starts to become a question of how much compatibility to the original QL you want to maintain. Certain things are expected at certain addresses, such as the RTC, Interrupt registers and mask - and the serial write reg...
- Wed Sep 29, 2021 5:32 pm
- Forum: Hardware
- Topic: Hermes status
- Replies: 87
- Views: 18086
Re: Hermes status
Damn! I could potentially have picked up thousands of these back in the 1990's. BT used 8749 as controller on their 30-channel PCM cards. Just before I left I scavenged a dozen of the cards thrown in a skip. They also used Ferranti ULAs - never found any info on them though. May be worth having a p...
Re: CAPSLED
I think this could be reduced to a single high efficiency LED and resistor...
- Tue Sep 21, 2021 2:39 pm
- Forum: Hardware
- Topic: Expanding the QL's address space beyond 1M (+primer on building QL compatible machines)
- Replies: 30
- Views: 8425
Re: Expanding the QL's address space beyond 1M (+primer on building QL compatible machines)
Added RAM Once the idea of extra RAM included on the motherboard is on the table, two obvious questions arise, which are what kind of RAM and how much. These are actually connected because of the available packaging and price the RAM comes in. In general, we are dealing with two types of RAM chips: ...
- Mon Sep 20, 2021 12:40 am
- Forum: Hardware
- Topic: New Sockets For Old
- Replies: 4
- Views: 1505
Re: New Sockets For Old
Exactly what should have been done from the start!mk79 wrote:Pretty all my QLs are Samsung builds and they used two cheap 24-pins sockets to host the CPU.