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by stephen_usher
Wed Sep 23, 2020 3:37 pm
Forum: HARDWARE DISCUSSIONS
Topic: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?
Replies: 26
Views: 358

Re: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?

OK, as I understand it, for the decode: Reset: The MMU asserts ROM for the first 4 read cycles. So, if ROM is asserted, along with RD, /AS, /UDS and /LDS I could stuff 0x0e into the top of the address bus and let the rest of the decode deal with itself. Address decode: If RD, /AS, /UDS and /LDS and ...
by stephen_usher
Wed Sep 23, 2020 3:26 pm
Forum: MEMBER BLOGS
Topic: Projects and Stuff
Replies: 133
Views: 22200

Re: Projects and Stuff

It's INCREADIBLY finicky.
by stephen_usher
Wed Sep 23, 2020 9:30 am
Forum: HARDWARE DISCUSSIONS
Topic: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?
Replies: 26
Views: 358

Re: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?

I just decode the whole address bus and address zero for ROM access. Think other decoders still use the GLUE to decode address zero, and not sure if they decode more than just the ROM area or not. Thanks. Have you considered @cmorley USB ROM board, or @DoG decoder.. would just seem easier than rein...
by stephen_usher
Tue Sep 22, 2020 11:23 pm
Forum: HARDWARE DISCUSSIONS
Topic: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?
Replies: 26
Views: 358

Re: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?

Out of interest, how does your decoder work, exxos ? Does it initially just trap addresses with A4 to A23 all zeros and change the address to 0x0e000000 and then set the correct signal (BGACK?) to the CPU when the ROM address range is accessed and enabling the ROM CE? I’m trying to think of the simp...
by stephen_usher
Tue Sep 22, 2020 6:07 pm
Forum: HARDWARE DISCUSSIONS
Topic: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?
Replies: 26
Views: 358

Re: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?

Well, having removed the Marpet RAM upgrade I can see better. There would be space in front of the power supply for the TF536 and to have a relocator board based upon derkom 's with the 68000 and also maybe the extra decode etc. circuitry too. It would require the socket for the TF536 to overlap the...
by stephen_usher
Mon Sep 21, 2020 11:15 pm
Forum: HARDWARE DISCUSSIONS
Topic: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?
Replies: 26
Views: 358

Re: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?

Without the top shield, I wonder if the TF536 could sit over the top of the shifter can. It might need a socket tower to get it up there though.. but then again the relocator/decode/ROM board could probably provide the height required.
by stephen_usher
Mon Sep 21, 2020 10:46 pm
Forum: HARDWARE DISCUSSIONS
Topic: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?
Replies: 26
Views: 358

Re: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?

Cyprian wrote:
Mon Sep 21, 2020 10:40 pm
If ram works fine on the ribbon cable, would be possible to use it also to relocate TF536?
You'd need to have two 32-way cables at least. The biggest problem would be with the clock I imagine.

There's a lot more going on with the CPU relative to the RAM.
by stephen_usher
Mon Sep 21, 2020 10:30 pm
Forum: HARDWARE DISCUSSIONS
Topic: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?
Replies: 26
Views: 358

Re: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?

I think that there's no way to have the top shield on with the TF536 anyway, looking at the clearances. And the RAM expansion (which I'll probably swap with an Exxos one and disable the on-board RAM) has some height to it too. IMG_2019.jpg How did you get the CPU connection over to that side of the ...
by stephen_usher
Mon Sep 21, 2020 9:19 pm
Forum: HARDWARE DISCUSSIONS
Topic: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?
Replies: 26
Views: 358

Re: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?

I'll have to get the experimental machine down from the loft and take a look at the layout. There will be an old RAM expansion to deal with too.
by stephen_usher
Mon Sep 21, 2020 7:42 pm
Forum: HARDWARE DISCUSSIONS
Topic: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?
Replies: 26
Views: 358

Re: Just wondering: TF536 CPU relocator+2.06 decode+ROM all on the one board?

Hmm.. some sort of shielded ribbon cable from the CPU location to the interface board? I guess timing and signal degradation may be the problem then. Probably not feasible actually.

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