Author Topic: Looking for people with an Amstrad and an UMC UM8272A as FDC  (Read 694 times)

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Offline roudoudou

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Hi
I'm looking for people owning a CPC/Plus with an UMC UM8272A as Floppy Disk Controler (neither a Nec nor a Zilog)
Cheers
use RASM, the best assembler ever made :p

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Offline Bryce

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All CPC were built with a µPD765. So you will only find an UM8272A in a CPC that has been repaired / converted.

Bryce.

Offline roudoudou

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All CPC were built with a µPD765. So you will only find an UM8272A in a CPC that has been repaired / converted.
Bryce.
So why cpcwiki page mention this chip?

i observe this on non-repaired machines
CPC 664 with Nec D765AC
CPC 6128 with Nec D765AC-2 or Zilog
6128 Plus were provided with Zilog version


use RASM, the best assembler ever made :p

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Offline Bryce

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No idea.

Bryce.

Offline gerald

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According to my list, I have two CPC (not Plus) with UM8272A (both manufactured in August 88)
According to my notes, these are not replacement part, but to check I'll have to reach them  :picard:   

[edit] I confirm, the motherboard I've just checked is pristine. Everything is wave soldered.
« Last Edit: 18:32, 06 May 21 by gerald »

Offline Bryce

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Ok, wasn't aware that they ever used 765 equivalents. Interesting.

Bryce.

Offline gerald

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According to my stat (from serviced motherboard) UM8272A ones are grouped between June 88 and March 89. Zilog ones are used during that time as well.
NEC seem to be used from the beginning up to June 86, replaced by Zilog.
« Last Edit: 22:04, 06 May 21 by gerald »

Online GUNHED

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Are there any known differences (regarding programming the FDC)?
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Offline roudoudou

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According to my stat (from serviced motherboard) UM8272A ones are grouped between June 88 and March 89. Zilog ones are used during that time as well.
NEC seem to be used from the beginning up to June 86, replaced by Zilog.
I opened all my stock and i found one with UM8272A, it's a CRTC-4
I hope it's working...
EDIT: do not turn ON with power  :-X
« Last Edit: 12:28, 07 May 21 by roudoudou »
use RASM, the best assembler ever made :p

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Offline roudoudou

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Are there any known differences (regarding programming the FDC)?
Zilog and Nec seems to have the same behaviour (in regular use)
UMC seems to have some differences

YEEESS i finally find one CPC with the chip (and working!)
use RASM, the best assembler ever made :p

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Offline Bryce

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UMC produced them under license, which means that they were given the schematic from the 765. So it should be 100% compatible. How does it react differently?

Bryce.

Offline TotO

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UMC produced them under license, which means that they were given the schematic from the 765.
So it should be 100% compatible. How does it react differently?
We can hear this rather logical argument, but which did not work for the CRTC.
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Offline Bryce

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We can hear this rather logical argument, but which did not work for the CRTC.

I don't think the 6845 was licensed to others. The others (all variants other than Motorola) made their own version which is why there are incompatibilities. These others were all companies capable of designing their own chips.

With UMC it's slightly different. Up to 1983 they were "only" a foundry - ie: they didn't have any design capability. In 1983 they opened Unicorn Microelectronics in San Jose, but even if they got everything up and running extremely fast, they would most likely only have got their own in-house designs on to the market by mid to late 1986. In 1987 they opened their first production facility in the US which is probably where their first own designed chips were being produced.


Bryce.

Offline TotO

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I don't think the 6845 was licensed to others. The others (all variants other than Motorola) made their own version which is why there are incompatibilities. These others were all companies capable of designing their own chips.
UMC, Zilog, Motorola, Nec... All was able to produce their own chip and/or customise them if required.
The MC6845 was not licence free. They are enough close (registers and pinout) to understand that was improved into the time.
About the CRTC, probably into the order: 2, 0, 1, 4, 3
About the FDC, probably minor fix was done.

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Offline Bryce

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UMC, Zilog, Motorola, Nec... All was able to produce their own chip and/or customise them if required.
The MC6845 was not licence free. They are enough close (registers and pinout) to understand that was improved into the time.
About the CRTC, probably into the order: 2, 0, 1, 4, 3
About the FDC, probably minor fix was done.

Eh, no. UMC weren't able to design their own chips until about 1986, but they were selling the 8272 before that, which means that it must have been a "die-copy" of the Motorola (or someone elses) design.

Bryce.

Offline TotO

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Eh, no. UMC weren't able to design their own chips until about 1986, but they were selling the 8272 before that, which means that it must have been a "die-copy" of the Motorola (or someone elses) design.
Hum... No, the CRTC 1 was produced by UMC in 1985. So, they were able to do the same with the 765.
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Offline Bryce

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Hum... No, the CRTC 1 was produced by UMC in 1985. So, they were able to do the same with the 765.

Ok. And is it identical to one of the other CRTC's? Or is it unique?

Bryce.

Offline TotO

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Ok. And is it identical to one of the other CRTC's? Or is it unique?
As I know, only UMC is "CRTC 1" and it consumes half the current compared to others.
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Offline Bryce

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Interesting. Is CRTC 1 (other than the current consumption) somehow different? The current consumption could be due to using a more modern process.

Bryce.
 

Offline TotO

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UMC has produced "CRTC0" clone (UM6845) and a revised version "CRTC1" (UM6845R).
The UM6845R features are described here: https://www.cpcwiki.eu/index.php/CRTC
Some modern CPC demo effects only works because they use the CRTC1.
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Offline roudoudou

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UMC has produced "CRTC0" clone (UM6845) and a revised version "CRTC1" (UM6845R).
The UM6845R features are described here: https://www.cpcwiki.eu/index.php/CRTC
Some modern CPC demo effects only works because they use the CRTC1.
Back in time, games like krafton&xunk or bob winner had trouble with CRTC versions. Hopefully they were fixed before release!!!
use RASM, the best assembler ever made :p

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Offline TotO

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Nice to know that.
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