Re: OctoRAM, High Speed SCSI and Zip GS

[lunatic@netcom.com (Lunatic Johnathan Bruce E'Sex)]

In article <1993Jan12.021932.25578@nuscc.nus.sg> ltchean@iss.nus.sg (Lim Thye Chean) writes:
>I am buying a High Speed SCSI card from my friend, to replace my Rev. C card,
>but encountered some problem. This is my configuration:
>
>ROM 1 GS, OctoRAM 2MB (256K simms), Zip GS (9MHz/32K), Rev.C SCSI, two
>harddisks (40MB Western Digital, 120MB Quantum), and a AI sound card.
[...]
>Thus I tried to switch off the DMA of High Speed SCSI, now it works. 
>So, I think it must be the DMA conflicts, but why? The friend I bought the
>card from also used OctoRAM, but he does not used a Zip GS. So...
>
>1. Is it because of Zip that cause the problem? 
>2. Is it because not all OctoRAM are the same (that is, some OctoRAM is
>   DMA-compatible and some are not)?
>3. Is it because of some other thing I am not aware of?
>4. Can I use RAMFast instead? 
 
 
 1: No, 2: No, 3: Yes, 4: Yes.
 
    ___
     |he OctoRAM is a standard eight bank RAM card.  That is, it
 doesn't do any weird tricks or have funny addressing.  DMA on the
 GS is normally possible in only the first four _BANKS_.  Most
 people say "first four megs," because by the time you get up to
 the fifth bank with any other RAM card you're already using 1 Meg
 chips in each bank.  The OctoRAM is the only card that I know of
 that will allow you to put 256K chips in the later four banks.
 And that's exactly what YOU have: Eight banks filled with 256K
 SIMMs.  With that configuration, you have one of four choices:
 1) Turn off DMA, 2) Turn off the second meg on your OctoRAM,
 3) Buy a couple of 1 Meg SIMMs to replace your eight 256K ones,
 4) Buy a RamFAST.  The RamFAST would work because it does some
 tricks to do DMA into all eight banks.

 FYI, I've got an OctoRAM w/ four 1 Meg SIMMs, Apple DMA SCSI card,
 and ZipGS 8/16 and they all work great together.

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