Uncreative Labs

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

I've been pondering whether or not it is time to update my XT with a solid state disk drive. I currently run a Future Domain TMC850M with SCSI HDD and CD-ROM. These days the IDE to CF (or even SD) adapters are getting very cheap. You can buy them for $5 on eBay. However, 16-bit IDE controllers for 8088 systems are rare...and honestly I like SCSI better.

SCSI to CF adapters do exist, but they are very expensive....usually in the $150 range. So, instead I am thinking of buying a SCSI to IDE bridge and using the IDE to CF adapter. The only down side to this route is that it requires two power connectors. But, I was just wondering if anyone in here has done a similar conversion that might have any good recommendations. The bridge I am looking at is made by ACARD.

Joined: 27 Jan 2007 Posts: 274 Location: USA

how big of a cf are you gona use, if its over 512, you might not get it to work with such an old ide card, might be stuck as low as 40mb with ide. but ive never tried it with compact flash though. as for using two adapters, might not be a good idea.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

I've seen people doubling up the adapters for use on their old macs. I think it should work well on a PC also. I am also pretty certain I can use more than 512mb. My host adapter supports at least 2GB drives...maybe even up to 8GB. The SCSI-->IDE adapter supports up to ATA-100, so I doubt that would be a bottleneck. The CF adapter doesn't seem to use any support chips, so it's more of a physical adapter than an electrical one.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Damn. I just found out that the SCSI-->IDE bridge I had my eyes on is only good for optical drives. The versions that can do IDE harddisks cost at least $70, which I find to be a little too expensive. Oh well, I'll just have to wait until somebody mass markets a SCSI to CF adapter.

Joined: 22 Apr 2007 Posts: 20

386er wrote:

how big of a cf are you gona use, if its over 512, you might not get it to work with such an old ide card, might be stuck as low as 40mb with ide. but ive never tried it with compact flash though. as for using two adapters, might not be a good idea.

I'm using a 340MB CF with mine, works just fine. I do get the feeling that 512 might just barely step over a limit somewhere, though.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Ah interesting. You already have flash in your XT. How is the performance compared to a traditional hard disk? The 8-bit bus on a 5160 motherboard is capable of something between 250-300k bytes/sec. My current harddisk and controller easily saturate the bus...does the flash slow things down at all?

Joined: 27 Jan 2007 Posts: 274 Location: USA

i dont think it be faster, hell, a standard xt harddrive is faster than its memory. besides, flash might wear out faster. but the good thing, when one flash drive is full, you can put in a new one.

Joined: 22 Apr 2007 Posts: 20

386er is mostly correct; the speed is faster than a typical MFM drive, but the speed of the ISA BUS eventually limits me to about 280KB/s.

Some people report speeds of up to 500KB/s using a bus-mastering SCSI controller that utilizes a memory window (ie. the disk transfers occur directly to RAM on the card that is mapped to the upper memory area in a000-e000), but I haven't gotten my hands on such a controller yet.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

A bus mastering 8-bit SCSI controller, eh? I've never heard of that before, though I'm sure one must exist. I wonder which one it could possibly be. I know the Future Domain based cards don't do DMA, but they are generally considered the best for driver support.
The ST01/02 doesn't do it, because they are based on Future domain.
I'm not sure about the Trantors, but my guess would be no. I have a T128, and played with it for quite a while. I think it benched about the same as my Future Domain. I'm not sure about the T130s though.
That would leave NCR and Rancho controllers. I haven't tried either of those. Is there something I'm missing?

Joined: 22 Apr 2007 Posts: 20

It's possible I'm missing something and not you. I was under the impression that the NCR-based chips used a memory hole in upper memory instead of DMA, which potentially makes them pretty darn fast.

I need to get my hands on more 8-bit SCSI controllers...

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

I guess you'll have to find one and test it out. I looked for information on ths NCR chips, but didn't see anything related to DMA. I would guess that if such a card exists, it could potentially be a problem for other devices that use the UMA.

Also, I haven't had much luck finding NCR SCSI controllers since every one I have seen has nad neither a boot ROM nor an internal connector.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Okay, well I'm back in the game for a SCSI flash drive. I didn't want to spend so much money, but I'm a little impatient. I found some ACARD AEC 2270U SCSI to IDE bridges on ebay for $40 (plus $10 shipping). I think they normally go for about $80 new. These bridges have hard disk support, and are pretty much guaranteed to work. Unfortunately I can't test until October though. I'll probably go with a 2GB CF card.

The alternative was getting a SCSI to PCMCIA adapter and a PCMCIA to CF adapter. This route works too, but it's not easy finding one that is guaranteed to be bootable (the ACARD solution is). I was considering buying a $10 (+ $10 shipping) SPYRUS RD300 PCMCIA adapter on ebay, but I found some documentation on the internet indicating that it might not work. I think it may require drivers, but I am not sure. I decided to spare myself the loss of $20, and just went with the ACARD. However, if somebody else wants to buy one and test it out, it would be an interesting learning experience Very Happy

ALSO.....

I was reading Vintage Computer Forum, and I found Trixter's comment about mbbrutman's memory mapped SCSI controller. As it turns out, Mike is a big fan of the TMC850 SCSI controllers. So, I did a search on the internet and sure enough, the TMC850 seems to support it. So, now the real mystery is how to enable it. I am certainly not getting 500kb/sec on my 5160. It must require a driver.

Joined: 21 Dec 2005 Posts: 66

I lurk here too ...

I'm a big fan of the Future Domain 850 series because the driver support is very good, performance is very good, and I've got versions that attach directly to both ISA machines and PCjrs.

Using a sequential read/write test that I wrote, I benchmarked reads running at around 300KB/sec and writes at around 150KB/sec. The machine is a PCjr running at 4.77 with a Nec V20 and a 544MB Fujitsu Hard disk. The hard disk really doesn't matter on a sequential read/write test - the point of the test is to test the bandwidth of the adapter, not the seek performance of the disk.

I think you'd be hard pressed to find any 8088 class machine running at 4.77Mhz that can do more than 280 or 300KB/sec to a hard disk. I did this exercise once before - take a minimally sized loop that can push data to memory and count the clock cycles it takes to execute the instructions and keep fetching the instructions. I should do it again and post the numbers ...

Tell me about this SCSI to IDE bridge - can you name your source?

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

I bought this one:

http://cgi.ebay.com/ACARD-Ultra-SCSI-to-IDE-Bridge-Card-Adapter-AEC-7720U_W0QQitemZ190143548197QQihZ009QQcategoryZ31494QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Though, this one should also work:

http://cgi.ebay.com/ACARD-ARS2000FU-Ultra-SCSI-50PINS-TO-IDE-BRIDGE_W0QQitemZ320151480484QQihZ011QQcategoryZ31494QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

There also used to be some Spyrus RD300 SCSI PCMCIA readers on ebay, that *May* work with a PCMCIA to CF adapter, but I'm not certain.

http://cgi.ebay.com/SPYRUS-RD300-External-PCMCIA-SCSI-NEW-IN-BOX_W0QQitemZ160147792631QQihZ006QQcategoryZ51082QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Joined: 21 Dec 2005 Posts: 66

Just to make sure I understand the plan:

8 bit ISA bus -> SCSI card -> Acard Adapter -> CF Flash

Something's going to break ...

Why not just stick with a SCSI drive in there? It wouldn't be solid state, but the 3.5" form factor drives consume much less energy than the monster 5.25" drive that was standard, and the performance and reliability are very good.