Re: VIC-II DRAM refresh

From: Francesco Messineo <>
Date: Sat, 15 Oct 2016 19:09:59 +0200
Message-ID: <>
On Sat, Oct 15, 2016 at 6:56 PM, Gerrit Heitsch
<> wrote:
> On 10/14/2016 07:16 PM, Francesco Messineo wrote:

>> yes, it was 8521 then. I'm sure at one point there was the 85xx
>> version of the 6526.
> Not 'there was', all 6526 after the end of '86 are internally 8521. They
> just labeled them 6526 again, probably to avoid confusion. You can check
> that by software, a timer IRQ behaves slightly different. Also, a good hint
> is the '206A' and '216A' after the datecode. The '2' indicates HMOS-II
> process. NMOS would have a '1' there.

good to know, I've never looked deep enough on these chip processes,
date codes and so on.

>> Even with TTL-compatible logic, they could invent any consistent
>> numbering, like XXYY257
>> instead of 7708 and XXYY258 instead of 7709...
>> For example, their 74LS245 equivalent was following that golden rule,
>> so at one point they decided to "go insane" on numbering.
> No really 'go insane', more along the lines of just counting up. The leading
> '7' means HMOS-I, the next '7' means 'support logic' and then just start
> from 00. 7700 was the 82S100-clone.

as I said, at one point, they were making the 65245 (I have a few
inside the VIC-20CR) and that is a replacement for the 74LS245. I'm
not sure what process they used on these.
Why not keeping the good practice and make a 77S100 for example? 77257
7706 and 77258 (just a few examples) would have been good too :)
I'm sure most of us have to keep a list of equivalents to avoid
putting the wrong replacement
(I do need it).


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Received on 2016-10-15 18:00:21

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