Author Topic: Questions about CRTCs, getting a better one if necessary, and 464 keyboard types  (Read 2881 times)

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Offline db6128

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I was just about to succumb to temptation and buy a SCART set and an HxC for my 6128 and perhaps occasionally my 464.
 
However, now I’m a little bit reluctant to order because I realised that I have no idea which CRTC either has (if the 464 had a better one, I’d move it into the 6128) and can’t check for a few days. Why reluctant, I don’t really know – I imagine that, even if they were both type 2s, I would buy the stuff and just try to find a 0 or 1 to transplant, rather than feeling like I had to get an entirely new CPC or something silly.
 
Which brings me to the questions: How easy is it to find a type 0 or 1; does anyone have pne, or a recommended source? I only saw a few Motorola 2s on eBay, for instance. And which, if either, of those two is considered ‘best’ overall, even if it’s just due to some tiny advantage or (hypothetical) capability? Of course, I’ve seen the articles here and on Grimware that go into some depth about the hardware and say that type 2 is the worst, but they don’t favour either of 0 or 1 that I’ve read.
 
Also, since I’ve remembered my poor old underused 464: I used to have two, one with each type of keyboard. I’m not sure, but I think the one I kept (nowadays I doubt I would get rid of any!) is the one with the high keys… which I think was because my silly (sillier) young self thought meant that they were ‘less worn down’ – how embarrassing! So, I’m just curious: Which is the newer one? Are there any likely advantages to either? I bet the one I have as a bad CRTC in it, for example.  :-X  I remember reading about this before, probably on the forum; I couldn’t see any specific information about individual models on the wiki.
 
Thanks in advance!
[The owner of one of the few existing cartridges of Chase HQ 2] mentioned to me that unless someone could find a way to guarantee the code wouldn't be duplicated to anyone else, he wouldn't be interested.
Did he also say things like "My treasureeeeee" and is he a little grey guy?

Offline Marq

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Just my two cents: if you intend to watch demos, there are a couple of recent top productions that are CRTC1 only. Some older ones tend to be for CRTC0. Most of the stuff I've tested works on both anyway.

Offline db6128

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Thanks. Demos aren’t my sole concern, or even a main one, but if there’s a certain CRTC out of type 0 or 1 that (theoretically) can run a greater proportion of all the software out there, I’d like to have that.
 
Of course, it all depends on what my two CPCs have, and if they’re both Motorolas, whether I can find a Hitachi or UMC instead. (I doubt either of the systems are late/rare enough to have a cost-down ASIC)
[The owner of one of the few existing cartridges of Chase HQ 2] mentioned to me that unless someone could find a way to guarantee the code wouldn't be duplicated to anyone else, he wouldn't be interested.
Did he also say things like "My treasureeeeee" and is he a little grey guy?

Offline Gryzor

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The taller keys were first.

Offline db6128

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There are two UMC 6845s listed on CPCTech: UM6845 (type 0) and UM6845R (type 1). I could (edit: did) get an R on eBay, in case I end up needing it (if both CPCs are type 2) or want a spare.
 
I can also see quite a few UM6845B models on eBay; does anyone know if the UM6845B is equivalent to the UM6845, and therefore a type 0? My logic is that I might as well buy a type 0 and a type 1 if I can find both. I can’t see any Hitachi type 0s, just these UM6845Bs that may or may not be equivalent.
 
Edit: there are also Hitachis, but they're marked either HD6845 with no S, HD6845P, HD6845SP, etc. Basically, are such variations usually equivalent/compatible?
« Last Edit: 20:55, 16 December 12 by db6128 »
[The owner of one of the few existing cartridges of Chase HQ 2] mentioned to me that unless someone could find a way to guarantee the code wouldn't be duplicated to anyone else, he wouldn't be interested.
Did he also say things like "My treasureeeeee" and is he a little grey guy?

Offline steve

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I have a vague recollection of seeing a post or picture on this forum from someone who had switchable CRTCs in their machine, does anyone else remember this or am I imagineing things.

Offline TFM

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IMHO I would suggest the CRTC type 0, it can do the most things. It's true that a lot of french productions tend to use CRTC 1. However other countries seem to adore CRTC 0 more.
 
Just don't use CRTC 2, which suxx.
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Offline arnoldemu

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There are two UMC 6845s listed on CPCTech: UM6845 (type 0) and UM6845R (type 1). I could (edit: did) get an R on eBay, in case I end up needing it (if both CPCs are type 2) or want a spare.
 
I can also see quite a few UM6845B models on eBay; does anyone know if the UM6845B is equivalent to the UM6845, and therefore a type 0? My logic is that I might as well buy a type 0 and a type 1 if I can find both. I can’t see any Hitachi type 0s, just these UM6845Bs that may or may not be equivalent.
 
Edit: there are also Hitachis, but they're marked either HD6845 with no S, HD6845P, HD6845SP, etc. Basically, are such variations usually equivalent/compatible?
HD6845 and HD6845SP should be ok. HD6845R is closer to the type 1.
Type 1 and type 0 are ok.

Old 464's with tall keys probably have type 0. Mine does.
Newer ones often have type 1, cost down have type 4.

6128 have all, 0, 1 and 2.
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Offline Bryce

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The 6845 was very popular on old CGA/EGA PC ISA graphic cards. If you want to get yourself some, just browse any car boot sale / flea market, you should still find them regularly for very little money. That's where I got most of mine :)

Bryce.

Offline db6128

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HD6845 and HD6845SP should be ok. HD6845R is closer to the type 1.
Type 1 and type 0 are ok.
Great, thanks! I’m now very impatient to check what my 6128 has, using a software-based diagnostic at first, I guess. In case it has a 2, I bought a UMC UM6845R, so that’s type 1 covered, and if your expectations are right, I might well have a type 0 waiting in the 464.

Quote
Old 464's with tall keys probably have type 0. Mine does.
Newer ones often have type 1, cost down have type 4.

6128 have all, 0, 1 and 2.
Yes, I read a site that I found linked from an older thread with similar questions that claims, contrary to what I thought based upon other reading, that the CRTC 2 was used in newer machines, not older ones; I guess Grimware’s page actually uses “original” to mean that Motorola made the first 6845, whereas I thought it meant Motorolas were used in CPCs first and replaced later.
 
The 6845 was very popular on old CGA/EGA PC ISA graphic cards. If you want to get yourself some, just browse any car boot sale / flea market, you should still find them regularly for very little money. That's where I got most of mine :)
Thanks for the very useful hint! I was already thinking today how I’m really looking forward to hitting the boot-sales for retro things as much as I can; it’s been too long. :D
[The owner of one of the few existing cartridges of Chase HQ 2] mentioned to me that unless someone could find a way to guarantee the code wouldn't be duplicated to anyone else, he wouldn't be interested.
Did he also say things like "My treasureeeeee" and is he a little grey guy?

Offline SyX

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I have a vague recollection of seeing a post or picture on this forum from someone who had switchable CRTCs in their machine, does anyone else remember this or am I imagineing things.
No, you are not imagining, jejeje. I have this multi-crtc machine (it was a present of CPCManiaco and Habi was the diabolical engineer :P ). It has the CRTCs 0,1 and 2; and i use it a lot for testing my CRTC depending code :)

Offline db6128

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According to Optimus’s CRTCtest, my 6128 has a 2 :/ whereas the 464 has a 0. I have a 1 on order, so I have all options covered, at least. But I think I’ll leave it until/if I have an essential reason to change.
 
Speaking of the 464, apparently all those years of disuse were not appreciated by its tape drive. At first I got a nonsensical slow wobbly noise, then it gradually sped up on each retry, and eventually it managed to load CRTCtest, somehow despite still being slow and amusingly wobbly (wow? flutter? whatever it’s called). Testament to the resilience of Amstrad’s loading format, I suppose, but not so much for the health of my player. What’s the prognosis for something like this? Does it happen often? I can’t see myself needing/wanting to use the 464 much, really, but it’s still a shame.
 
Copying this to the clipboard just in case the forum decides to send me forward to a blank page and tell me I have to type something (again).
[The owner of one of the few existing cartridges of Chase HQ 2] mentioned to me that unless someone could find a way to guarantee the code wouldn't be duplicated to anyone else, he wouldn't be interested.
Did he also say things like "My treasureeeeee" and is he a little grey guy?

Offline Bryce

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Just like the Floppy drives, the tape drives should be get a service after years of non-use. They also have a belt that dis-integrates over the years and should be changed. You should remove any dirt / fluff inside mechanism, put some new grease (vaseline works best) on the teeth of the cogs and you should clean both heads (play and record) and the pinch wheels using spirits (alcohol) on a cotton bud. After that it should work like new.

Bryce.   

Offline db6128

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Thanks, Bryce. I should re-emphasise how impressed I was that it was eventually able to load the tape despite the, er, heavy operatic colouration. :D
[The owner of one of the few existing cartridges of Chase HQ 2] mentioned to me that unless someone could find a way to guarantee the code wouldn't be duplicated to anyone else, he wouldn't be interested.
Did he also say things like "My treasureeeeee" and is he a little grey guy?