GVP A4008 SCSI Controller

Karl Jeacle

April 1994

For the last year, `Amiga Format' had been telling me how great the world of Amiga CD was, and now the Amiga CD32 was here. After seeing the October 1993 Fresh Fish CD being demonstrated at CUGI, I decided it was finally time to give in, and get a CD-ROM for my Amiga.

First however, I'd need a SCSI controller. After quite a bit of research, I eventually choose GVP's A4008 card. I ordered it from `Amigaman' in the USA. They charged US$159 for the board and US$20 for shipping and insurance. My credit card was charged a total of IR#128.01. It took about 6 weeks to get here, but this was probably due to the overloaded postal system during the Christmas holidays.

Decisions... Decisions...

What should have been a reasonably simple case of just going out and buying a SCSI controller for my A4000 turned out to be a rather more complicated process than I had originally forseen.

The only two SCSI cards I was aware of for the Amiga 4000 were Commodore's (now DKB's) A4091 and the Fastlane Z3. I'd read good reviews of the Fastlane board, and knew it was already in the shops, however prices were in the range of US$599 or STG#399 --- slightly more than I was prepared to spend just to get a CDROM attached! The A4091 board seemed to be in very short supply, but was significantly cheaper. Both of these cards were Zorro-III (A3000/A4000 only) SCSI-II controller cards.

Things started to get tricky when I discovered that early models of the A4000 were shipped with a broken Buster chip which prevented many Zorro-III boards from working correctly. The revision which had this problem was `Rev 9', and sure enough this was in my machine. To make matters worse, my Buster was surface mounted, so despite the fact that Commodore were aware of this problem, and were distributing new Busters with the A4091 card, my A4000 was too old and didn't have a socketed chip that could be easily replaced. The Fastlane card, on the other hand, was smart. It knew about the broken Busters and had a work-around to compensate. Performance wouldn't be quite as good as with a fully functional Buster, but the card would still work well.

All of this meant that the A4091 just wasn't an option for me. The Fastlane Z3 card would work perfectly, but it was too expensive. I'd have to look for a Zorro-II SCSI-I card for the A2000 which would hopefully still work in an A4000.

The problem with old Zorro-II cards for the A2000 is that the Amiga 4000's 32-bit RAM is outside of the 24-bit DMA-able address space which these controller cards can see, so data can't be transferred directly from the SCSI device into main memory. This means the CPU ends up dealing with requests and individually copying a few bytes at a time to and from 32-bit memory. The transfer rates are abysmal.

One fix for this is a Shareware program by Barry McConnell called DMAfix which patches some DOS library calls to do the CPU copies with larger buffers. This improves performance significantly. It works fine with cards like the A2091, but this whole scenario seemed quite unappealing to me.

Finally, I saw an advert for GVP's A4008 card. It was cheaper than the other A4000 cards, and was seemingly designed with the A4000 in mind, so it was definately worth a look.

GVP Hardware

The A4008 turned out to be a reworked GVP HC8+ card. It's a full length Zorro-II card with space to mount a 3.5" hard disk onboard, and SIMM sockets to install up to 8Mb of 16-bit RAM in 2Mb increments. The external connector is a standard DB-25 Female affair. Internally is a 50-pin male header which accepts standard SCSI ribbon cables, and a power plug for onboard drives.

The card overcomes DMA problems by essentially building DMAfix functionality into the card itself. Although, this is still a bit of a hack, I preferred this hardware solution to having to run a program which would patch OS calls every time I'd boot up.

Installing the card was no trouble at all. The only possible things to configure are some of the jumpers to say how much memory is on the board or whether or not you want AutoBoot enabled. The card worked first time for me when I plugged it in.

The Documentation

Documentation is up to GVP's usual high standard. There is a 14 page booklet on installing the card itself, and a 68 page manual on the FaaastPREP 2.0 software for preparing and formatting hard drives.

Both documents contain lots of useful information for the novice user.

The Software

Software for the card comes on a single floppy with a Commodore Installer script provided to do the dirty work. There's not much to it though. It copies the binddrivers version of the gvpscsi driver into the Expansion drawer, and asks you if you want to install any of the GVP support software (such as the HD preparation software). One thing it does ask, is if you are on an A4000, you can choose what sort of RAM it uses to allocate buffers. Naturally it suggest defaulting to Chip RAM given the problems which will arise if you use 32-bit Fast RAM.

While I've heard people swear by GVP's FaaastPREP software, I didn't have too much patience for it myself. First thing I noticed was that it had never heard of DCFS. Apparently, the software was taken straight from the A2000 series cards. A long time HDToolBox user, I just used it instead with command line arguments to specify the alternative SCSI device (gvpscsi.device). To be fair though, the software is quite extensive. It comes in two separate programs: FastPrep and ExpertPrep. FastPrep will make most of the decisions for you and automate the hard drive installation process, while ExpertPrep can be used later if desired to fine tune your hard drive.

Other software provided on the Install disk includes a memory test program for onboard RAM and GVP's GVPinfo program which tells you all kinds of things about your Amiga. It identifies the A4008 as "GVP Impact Series-II SCSI DMA".


As far as performance of the card is concerned, I have really only been using it with a CDROM drive, which is obviously not pushing the card to any limits. I did have an old Quantum 105S installed for a few days and was getting transfer rates of around 700Kbytes/sec.

Overall, I'm happy with the A4008. It's a reasonably cheap SCSI solution for the A4000 that just plugs in and goes without any DMA problems. For people who don't want to spend a fortune just to get a SCSI interface and for those not concerned about getting power-user performance from faster devices, the GVP card is a pretty safe bet.