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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: mikeymike on August 27, 2009, 04:08:45 PM

Title: A1200, ide dma
Post by: mikeymike on August 27, 2009, 04:08:45 PM

I noticed the other day that the SCSI kit for the Blizzard 12xx enables one to have a SCSI hard disk that can do DMA.  Why wasn't anything done to allow IDE DMA, does anyone know?

Title: Re: A1200, ide dma
Post by: amiga1260 on August 27, 2009, 04:25:01 PM

When Commodore built the A1200, A600 and A4000 there wasn't any DMA IDE only PIO DMA.

SCSI were in those days the most popular for storage media.

I think it's possible to bulit a DMA IDE controller for the A1200, but it must be connected to an accelerator card.

Title: Re: A1200, ide dma
Post by: tone007 on August 27, 2009, 04:25:48 PM

My guess is back then, external SCSI devices were far more popular than external IDE devices.

Title: Re: A1200, ide dma
Post by: platon42 on August 27, 2009, 04:48:55 PM

Quote from: mikeymike;521087

I noticed the other day that the SCSI kit for the Blizzard 12xx enables one to have a SCSI hard disk that can do DMA.  Why wasn't anything done to allow IDE DMA, does anyone know?

Despite it was not available at the time, it would have needed additional logic for bus arbitration (something like the Buster chip) and that would not have been as cheap as the implementation in the A1200 Gayle (?) chip.

Anyway, I suppose you know that there are rather cheap adapters for SCSI to IDE, so you can use cheap IDE harddisks on the scsi bus?

Title: Re: A1200, ide dma
Post by: mikeymike on August 27, 2009, 07:47:31 PM

I would still need a SCSI bus :)

Although this interests me considering I'm thinking of taking my A500 out of retirement (provided the clock battery hasn't melted it).  What is 'cheap'?