jt19840@tut.fi (Tuomi Jyrki Juhani) (01/11/89)
I have installed a Bocaram AT Extended/Expanded memory board in a Hyundai 286C AT-compatible and I am having problems using the board's EMS memory. Below is a description of the hardware and my evaluation of the situation. However, I am lacking sufficient hardware knowledge to fully understand the issues involved. I am welcoming any comments and additional infor- mation on the situation. Bocaram AT is a EMS 4.0 compatible combined conventional/expanded/extended memory board with 2 MB capability using 256KBit chips (4 MB with a piggy- back board). Manufacturer claims that the board can be populated using 150 ns chips and be run with clock speeds upto 24 MHz. This is said to be possible because the board inserts wait states on the bus as necessary. The reason why I acquired this board is because I had some 150ns chips left over from the era when DRAM was cheap (or at least reasonably priced :-) Support software is version 1.5. On-board memory can be configured as conventional memory to backfill from 512K to 640K, as expanded memory (upto 2 MB per board), and as extended memory. All these can co-exist simultaneously, if so configured. Hyundai 286C is a 10/8 MHz one wait state AT compatible. It is based on C&T chipset with Award BIOS (3.02j) and kbd controller. Floppy ctrl is on the mother board. Other boards in the machine are: - ATI EGA Wonder - WD 1003-WAH disk ctrl I have two rows of 150ns RAM chips and two rows of 120ns chips. Using the board for extended memory ONLY works fine with both types of chips, i.e. 512KB of 150ns memory, or 512KB of 120ns memory, or 1024KB with mixture of both chips speeds, all work with no problems at all. Now, if the board is configured as expanded memory, or as combined expanded/ extended memory, the expanded memory will not work. The EMS driver recog- nizes the board but does not find the memory, i.e. the driver aborts with the following boot-time messages: 0 pages found on EMS board at 0268 EMS compatible boards found = 1 The technical support of the local importer (in Finland) tried the board - as I had configured it - in another 10 MHz AT clone and the board worked perfect- ly. They said that they had sold several Bocaram AT boards for use with various brands of AT clones (IBM too!) and didn't know of any problems. However, I know of another Hyundai 286C/Bocaram AT-combination with this same problem, so I am fairly confident that the problem is not caused by individual machines and/or boards. The representatives of the importer suspected that the Hyundai AT does not recognize the method that Bocaram board uses to insert wait states on the bus. I don't know enough of hardware to comment on this. Now I have found out that if I lower the machine's clock speed to 8MHz and use 120ns chips for EMS memory, everything works all right! It sure feels silly to drive with brakes on to make things work! From this I am guessing that if I will buy 100ns chips, the expanded memory will probably work fine even at the 10MHz speed. Yes, so much for Bocaram's claims to be able to use 150ns chips... So, if you have any suggestions on why this combination won't work properly, I would appreciate hearing (or reading :-) them. Some things that I have already tried (and which don't change the board's behaviour at all): - switching IBM EGA card in place of ATI card - setting jumper JP2 to cover pins 1 and 2 (should be done in machines operating at speeds greater than 12MHz) I have not encountered any other compatibility problems with the Hyundai 286C. Jyrki Tuomi