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From: castorca@EA.USL.EDU (Christian Castor)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: NEC V20 chip
Message-ID: <00939185.F1C71360@EA.USL.EDU>
Date: 3 Jul 90 04:43:24 GMT
References: <00938EEE.F9719E80@EA.USL.EDU>,<11428@netcom.UUCP>
Sender: anon@rouge.usl.edu
Reply-To: castorca@EA.USL.EDU (Christian Castor)
Organization: Univ. of Southwestern Louisiana
Lines: 66

In article <11428@netcom.UUCP>, mcmahan@netcom.UUCP (Dave Mc Mahan) writes:
>
> In a previous article, castorca@EA.USL.EDU (Christian Castor) writes:
>>
>>I have an A2088 bridgeboard. Someone told me that if I took
>>out the Intel 8088 chip from the BB, and replace it with
>>a NEC V20 chip (5 MHz), the board would increase its 
>>speed a little bit. 
>>   I got two V20 chips mail order, and neither worked. When
>>I plug in the V20, the BB boots, but it reports that there
>>is an error in a 64K RAM address. After that, the entire
>>system freezes.  When I replaced the Intel 8088, everything
>>ran OK.
>>Anyone knows the cause of this problem?
>>(My bridgeboard has the old (1988) Janus chips and software).
>>Also, I noted that the chip number of my V20s is D70108D-5, 
>>while the chip number on a catalog is D70108C-5. 
>>Thanx in advance.
>
>I have been told that this is because the V20 wants to see 50% duty-cycle
>clock cycles.  The bridgeboard produces about 30% duty cycles.  I have no
>idea if this is the true problem or not.  My experiences with V20 chips have
>been that it does speed up the computer, but nothing noticable unless you
>use a program like Norton Utilities to actually measure it.
>
>
>>-Chris
>
>   -dave

The following is EMail I received from eddy@duteca.tudelft.nl (Eddy Olk):
(Thank you, Eddy).

] I tried this too (seeking for more speed) and it didn't work for me
] either. My bridgeboard behaved different though, it found the first
] 256K of RAM (so it forgot about the second 256K) and the screen was filled
] with random characters at random places. I think my bridgeboard behaved
] differently because I used an 8 MHz V20. Anyway it (sadly) didn't work.
] The problem is caused by a timing bug (at least I think it is) in the
] Ferranti FE-2010 chip. The chip will function OK with 8088's but will
] fail for V20's due to the slightly different timing of the V20.
] However, the Ferranti FE-2010-A (watch the A!) used in newer bridgeboards
] has no problems with the V20. So replacing the FE-2010 by a FE-2010-A will
] make the V20 work in a bridgeboard.
] BTW there are ways to speed up the bridgeboard even more. A german
] company sells upgrade sets which allow the bridgeboard to run at 8 MHz (or
] since recently even 12 MHz) with a V20. Personally I'm not seeking more
] bridgeboard performance anymore since I'm increasingly using the Amiga side
] (which has multitasking and other goodies :-).

   Well, it seems I'll have to go for the Ferranti chip. I've
heard that the V20 will increase the Norton index from 1.0
to 1.8.  What advantage does that represents in reality? I
got a 30 day money back guarantee, so if this stuff is not
worth, I better return it ASAP (and stick with ol' Ami 8^).

Thank you all for sharing your wisdom.

-Chris

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