Modding A1200: IDE vs SCSI-II performance?

[Silver]

Hi,

The time has come to mod my A1200 (I've been working through most other systems I own).

I've got a A1200 with a Blizzard 030@50, 32MB RAM, scsi-ii kit.

I'm planning to ditch the old scsi and ide drives, hook up a internal compact flash (or 2) and an internal slimline cdrom (because you can!) and mod in a atx psu (pico-psu or similar).


Question is - should I ditch the scsi kit, and hook up the CF and cd via IDE, or I have a couple of IDE>SCSI adapters (Acard adapters) that I see work to attach IDE devices to the scsi chain. So I could go CF-IDE adapter>SCSI adapter>Blizzard, and the cdrom could do the same or just go ide only as it won't get much use.

I've read that the blizzard scsi allows for dma access to the drives - but is this going to be at all noticable? Anything I need to consider?

I'm aiming for a nice compact A1200 choc full of WHDload goodness...

[TheCorfiot]

@silver,

I think you've answered your own questions really,

Although the Blizzards SCSI will outperform the IDE by far, You also want a compact solution & the use of a low power quiet CF HD.

So i guess it will be onboard IDE then, you can check out the IDEFix express at amigakit, it's a bit faster than the std 4-way interface but again won't be anywhere near SCSI performance.

If you are after a WHDLoad "Games" machine then IDE I think will be sufficient & cost effective.

[adolescent]

The Blizzard SCSI is not only faster, but uses less CPU (DMA). I'd see if you can find one of the OEM Acard adapters that does SCSI to IDE on a 3.5" frame (I've been looking off and on for a while now).

[Damion]

So I could go CF-IDE adapter>SCSI adapter>Blizzard,

That's what I would do.

I'm using an IDE-Fix Express on mine, it's OK (still boots in seconds) but the Blizzard SCSI is faster and eats a lot less CPU. If you're running something CPU intensive and need to access your drives, copying large files around, etc, the SCSI will come in handy.

[Silver]

Thanks for the quick responses.....

I should have said - even if I stick with scsi, I'm planning on making it all internal anyway.

I have the small acard scsi-ide adapters - just a pcb, no frame - but I reckon it could all be packed in somehow. Why do you want them on a 3.5 frame?

I have some concerns of the IDE>scsi overhead, but reading it the specs it can far exceed the amigas transfer rate anway.

Should I stick the cdrom on scsi too? How do you make a a1200 boot cd32 cd's?

[laser]

btw,

is there available on any place any kind of scsi > CF adapter ?

of course to use a CF card on the SCSI instead IDE

[Damion]

I have some concerns of the IDE>scsi overhead, but reading it the specs it can far exceed the amigas transfer rate anway.

Just to ease your mind, I've run Acard adapters on a few different Amigas, and they perform flawlessly. There is _NO_ detectable difference in feel, or in the benchmarks I've run (which show rates near the theoretical maximums of the controllers I've tested, much better than old SCSI drives). As far as CF -> IDE -> SCSI, that also works great. Just make sure your adapter and CF card are DMA capable, and you are set.

[Silver]

Originally Posted by laser

btw,

is there available on any place any kind of scsi > CF adapter ?

of course to use a CF card on the SCSI instead IDE

Actually there is no difference between a CF>SCSI and IDE>SCSI adapter.

All compact flash cards can operate in 2 modes - a "memory card" mode or a "True IDE" mode. It's set by setting one or 2 of the pins high I believe.

All compact flash to IDE adapters do is set these pins (to turn on TrueIDE mode) and route the pins to a standard 40pin (or 44pin) IDE connector. They are completely passive - all the electronics is inside the compact flash card.

So a CF->SCSI adapter is simply a IDE->SCSI adapter, like the acard.

(Technically you could get "memory card mode" cf to scsi adapter, but you would have to make it appear as a drive of some type, so you may as well use CF's inbuilt ide feature...)

This TrueIDE feature (it's part of the CF spec) is what makes CF cards so used & useful - they work great with anicent Pc's etc or anything with a IDE interface. (There is an exception to this, to do with with how most cf cards identify themselves when in ide mode, which prevented me getting one working for ages when I was modding a N64/Z64 setup, but usually it's not relevant)

[Silver]

Originally Posted by Damion

Just to ease your mind, I've run Acard adapters on a few different Amigas, and they perform flawlessly. There is _NO_ detectable difference in feel, or in the benchmarks I've run (which show rates near the theoretical maximums of the controllers I've tested, much better than old SCSI drives). As far as CF -> IDE -> SCSI, that also works great. Just make sure your adapter and CF card are DMA capable, and you are set.

That's good to hear. How do you identify whether a CF card is DMA capable in IDE mode?

As far as I understand (see above post) CF-IDE adapters are simply passive wiring devices - surely any CF-IDE adapter will work, or am I missing something?

[Damion]

Originally Posted by Silver

That's good to hear. How do you identify whether a CF card is DMA capable in IDE mode?

Good question! I can't say for certain, but I know SanDisk 1 GB, 2 GB, and 2 GB "Ultra" cards do.

ACS claims their adapters can utilize DMA with certain SanDisk cards.

As far as I understand (see above post) CF-IDE adapters are simply passive wiring devices - surely any CF-IDE adapter will work, or am I missing something?

Nope, unfortunately some of the cheaper adapters are PIO only. (Just fine for A1200/A4000 internal IDE, though). Those from Addonics or Mesa will definitely handle it (the Mesa cards even have DMA enable/disable jumpers), but basically, just make sure the product literature specifically states that it's supported. On my A2K/GVP HC+8, there is about 80% free CPU with a Mesa adapter and SanDisk 1 GB card... on a bone-stock 68000.

[Toni Wilen]

IDE transfers are completely "hidden" behind SCSI-IDE adapter. (at least if using "intelligent" adapter like ACard)

CF PIO or DMA IDE mode has no difference in Amiga CPU usage. (and PIO4 is usually faster than most Amiga SCSI adapter's bandwidth)

[Silver]

Originally Posted by Damion

Nope, unfortunately some of the cheaper adapters are PIO only. (Just fine for A1200/A4000 internal IDE, though). Those from Addonics or Mesa will definitely handle it (the Mesa cards even have DMA enable/disable jumpers), but basically, just make sure the product literature specifically states that it's supported. On my A2K/GVP HC+8, there is about 80% free CPU with a Mesa adapter and SanDisk 1 GB card... on a bone-stock 68000.

Hmmmm. I'm not convinced - looking at the CF-IDE adapters on the Mesa page you linked to, I can't see any active electronics on the boards. some surface mount caps/resistors maybe - but essentially it's just wiring the CF to the IDE socket.

It could be there are pins that need to be held at certain voltages etc which the cheap adapters don't do, but I can't see an adapter allowing DMA or not...?

[Silver]

Originally Posted by Toni Wilen

IDE transfers are completely "hidden" behind SCSI-IDE adapter. (at least if using "intelligent" adapter like ACard)

Yes I realise - DMA only an advantage if you are connecting to the Amiga's IDE; otherwise it's all down the adapter and it's compataibility (or not) with the CF card.

CF PIO or DMA IDE mode has no difference in Amiga CPU usage. (and PIO4 is usually faster than most Amiga SCSI adapter's bandwidth)

That's interesting - PIO4 over IDE beats SCSI-2 throughput with DMA? I guess both are fast enough to be bottlenecked elsewhere in the amiga...

[Damion]

Originally Posted by Toni Wilen

IDE transfers are completely "hidden" behind SCSI-IDE adapter. (at least if using "intelligent" adapter like ACard)

CF PIO or DMA IDE mode has no difference in Amiga CPU usage. (and PIO4 is usually faster than most Amiga SCSI adapter's bandwidth)

Hmmm, that would make sense, the SCSI->IDE adapter handles DMA irregardless of what is set on the IDE end (in which case pretty much everything I said can be ignored for Amiga use, LOL).

Just for kicks, I tried benchmarking both with and without the DMA jumper enabled on my CF->IDE adapter, but I can't get the machine to boot with the jumper disabled... it simply hangs forever with the HD light on. :/

[Damion]

Originally Posted by Silver

Hmmmm. I'm not convinced - looking at the CF-IDE adapters on the Mesa page you linked to, I can't see any active electronics on the boards. some surface mount caps/resistors maybe - but essentially it's just wiring the CF to the IDE socket.

It could be there are pins that need to be held at certain voltages etc which the cheap adapters don't do, but I can't see an adapter allowing DMA or not...?

My understanding is the CF spec doesn't specifically call for DMA, only PIO. Regardless, on some cheap adapters, the required pins on the IDE header for DMA simply don't go anywhere. The card has to support it as well... though by now most probably do.

However, if what Toni is saying is correct (and I'm sure it is) it makes no difference for Amiga use, anyway.

[Silver]

Originally Posted by Damion

My understanding is the CF spec doesn't specifically call for DMA, only PIO. Regardless, on some cheap adapters, the required pins on the IDE header for DMA simply don't go anywhere. The card has to support it as well... though by now most probably do.

However, if what Toni is saying is correct (and I'm sure it is) it makes no difference for Amiga use, anyway.

Yes you are quite right - a quick trip to the CFA website - http://www.compactflash.org/ - shows the latest spec (4.1) means cards can support Ultra DMA 133.

I know that rev2.0 of the spec did not mention DMA - so adapters designed round older spec will not support DMA at all. Makes sense.

[Calgor]

@Silver

Seems like you have a similar idea as myself on a whdload A1200.

I currently have a Blizzard IV 030/50 + SCSI Kit + FastATA MK-III, with a fast hard drive hooked up to the fastata and a scsi cdrw hooked up to the blizzard.

What I can tell you is that when transferring huge files, the computer slows to a crawl due to the fastata not using DMA (though this is not really important when using whdload - so depends on your preferences). Maybe it would be a lot better with an 060, or if I try to force a slower PIO mode.

I wanted to hook up an Acard SCSI-IDE adapter internally to the 2.5inch HD, but am not sure if it will fit inside the case. I think it would be the 50 pin acard adapter - I only have the 68 pin ones. Have you found it will fit? (I suppose it would if you use a CF adapter that fits parallel).

[Silver]

Originally Posted by Calgor

I wanted to hook up an Acard SCSI-IDE adapter internally to the 2.5inch HD, but am not sure if it will fit inside the case. I think it would be the 50 pin acard adapter - I only have the 68 pin ones. Have you found it will fit? (I suppose it would if you use a CF adapter that fits parallel).

I have the 50pin version, it's still fairly chunky. To be honest I have not opened up my a1200 so I'm not familiar with space issues... I was thinking worst case I could attach it flat somewhere and run cables to and from the adapter....

[rkauer]

Originally Posted by Silver

I have the 50pin version, it's still fairly chunky. To be honest I have not opened up my a1200 so I'm not familiar with space issues... I was thinking worst case I could attach it flat somewhere and run cables to and from the adapter....

Tips: install a gender changer in the SCSI kit, then the acard over it and route a cable to the IDE HD. If your HD is 44pin, buy a small and cheap 40>44pin adapter.

Prefer to use a cable with built-in active terminators.

[Silver]

Originally Posted by rkauer

Tips: install a gender changer in the SCSI kit, then the acard over it and route a cable to the IDE HD. If your HD is 44pin, buy a small and cheap 40>44pin adapter.

Prefer to use a cable with built-in active terminators.

Ok thanks for the tip. I was hoping to make a 50pin cable going from the acard to the scsi-kit (and it's non-scsi standard 25pin connector). If not looks like I need a scsi adapter that goes from female-25pin to male-50pin to plug in to the acard.

Get's more complicated if I had the cdrom to the scsi chain...