I've been hunting around in my old component stock and found a tube of unused 4864 DRAM 16 pin DIP devices.
However, these are 4864P-3 which I understand are about 25% slower than 4864P-2.
My assumption is that Sinclair used the faster devices for good reason and the -3 devices won't cut it in a QL. Would I be right?
150ns access time / 270 ns cycle time, vs 200 ns and 335 ns. Using the -3 is effectively overclocking them? I'm sure QL bus isn't that quick.
4864 DRAM
-
Barbarpapa1
- ROM Dongle
- Posts: 9
- Joined: Tue Feb 06, 2024 6:24 am
- Contact:
Re: 4864 DRAM
Hello
I’m not computer hardware expert of any kind, but on Slovene computer forum I presented my QL restoration. One of forum members has deep knowledge of QL hardware and he mentioned that QL is full of unexpected and innovative solutions. He specially emphasized how important is RAM timing for QL-s picture generation. QL is apparently only home computer of its generation that uses burst page access to RAM for picture generation. The RAM timing is responsible for slightly inappropriate video timing in 512 X 256 mode (the picture is normally cut away on the right side). And with use of mentioned burst page access QL manages to squeeze slightly more data for video generation as Atari ST, despite Atari’s double data bus width, compared to the QL.
So the narrative is, RAM timing is very important for the QL…
Have a nice evening…
Jože
I’m not computer hardware expert of any kind, but on Slovene computer forum I presented my QL restoration. One of forum members has deep knowledge of QL hardware and he mentioned that QL is full of unexpected and innovative solutions. He specially emphasized how important is RAM timing for QL-s picture generation. QL is apparently only home computer of its generation that uses burst page access to RAM for picture generation. The RAM timing is responsible for slightly inappropriate video timing in 512 X 256 mode (the picture is normally cut away on the right side). And with use of mentioned burst page access QL manages to squeeze slightly more data for video generation as Atari ST, despite Atari’s double data bus width, compared to the QL.
So the narrative is, RAM timing is very important for the QL…
Have a nice evening…
Jože
-
AndrewLambert
- ROM Dongle
- Posts: 14
- Joined: Wed Jan 17, 2024 2:01 pm
Re: 4864 DRAM
The RAM in the QL was the absolute least they could get away with. Everything is marginal. With the incredibly poor power and debounce practices used, the QL seems to spend almost all its life only just working.
Some early FB QLs had -200 DRAM, but they quickly switched to -150 and some of the very late QLs had -120 on occasion. That was exclusively Samsung production from what I have seen so far.
Some early FB QLs had -200 DRAM, but they quickly switched to -150 and some of the very late QLs had -120 on occasion. That was exclusively Samsung production from what I have seen so far.
Re: 4864 DRAM
I dug through my notes and found the following:
D06- had NEC UPD4164C-3 (seen once)
D06- had Hitachi HM4864P2
D09- had Siemens HYB4164P2
D09- had TI TMS4164-15NL (most common)
D09- had Mostek MK4564-15
S18- had TI TMS4164-12NL
Others I haven't seen but listed in the service manual include MCM6665AP15 by Motorola and MSM3764-15RS by OKI.
Generally, any of the standard 4164 clones in the 120 - 150nS speed grades are preferable.
D06- had NEC UPD4164C-3 (seen once)
D06- had Hitachi HM4864P2
D09- had Siemens HYB4164P2
D09- had TI TMS4164-15NL (most common)
D09- had Mostek MK4564-15
S18- had TI TMS4164-12NL
Others I haven't seen but listed in the service manual include MCM6665AP15 by Motorola and MSM3764-15RS by OKI.
Generally, any of the standard 4164 clones in the 120 - 150nS speed grades are preferable.