Mike_Wilson@CARLETON.BITNET (Mike Wilson) (06/13/86)
Hi,
I'm currently working on a project to port a new version of Smalltalk
(examplar-based, multiple inheritance, multiple PROCESSOR, for those who
are interested) to multiple 68000's on the VME bus. Currently we are
doing our development on Apple Mac "XL"s, but we are investigating the
use of other machines (because the Lisas are reaching the end of their
useful lifespan, and support is lousy!).
The ATARI 1040 (or 520 for that matter) seems like a reasonable choice,
except for the question of memory. You see, the Smalltalk image alone (ie.
without *any* code to execute it) is well over 900K long, so unless we can
expand memory to at least 2Meg, we can't use them.
So... My question is: What is the current (read: "Right Now!") limit on
the amount of expansion memory which is supported by the ATARI?
By the way, an offshoot of this project would probably be a working
Smalltalk for all ATARIs (Once it works, we could always prune it down to
fit).
.Mikerb@cci632.UUCP (06/25/86)
In article <8606131855.AA04757@ucbvax.Berkeley.EDU> Mike_Wilson@CARLETON.BITNET (Mike Wilson) writes: >Hi, > I'm currently working on a project to port a new version of Smalltalk >(examplar-based, multiple inheritance, multiple PROCESSOR, for those who >are interested) to multiple 68000's on the VME bus. Currently we are >doing our development on Apple Mac "XL"s, but we are investigating the >use of other machines (because the Lisas are reaching the end of their >useful lifespan, and support is lousy!). > > The ATARI 1040 (or 520 for that matter) seems like a reasonable choice, >except for the question of memory. You see, the Smalltalk image alone (ie. >without *any* code to execute it) is well over 900K long, so unless we can >expand memory to at least 2Meg, we can't use them. According to Abacus literature, the ST series is capable of supporting 4 megabytes, using 1 megabit chips. Caveat here, these must be 1meg by X not 256x4 or some similar arrangement. There are 20 address lines plus two RAS and two CAS lines. The MMU doesn't know how to handle 4 banks of 256x16, but it does appearantly know how to handle 1megx16. There is no question that, using 1meg by X chips, you can get at least 2 meg stuffed in there. You could simplify things by getting SIP hybrids. > So... My question is: What is the current (read: "Right Now!") limit on >the amount of expansion memory which is supported by the ATARI? If you are willing to rebuild the ram banks completely (modest price, some labor), you can safely get 2 meg for sure. Getting 4 meg depends on current requirements of the rams, access times, and general loading/timing requirements of the 1 meg chips. > By the way, an offshoot of this project would probably be a working >Smalltalk for all ATARIs (Once it works, we could always prune it down to >fit). Looking forward to it. ATARI: Have you started putting the holes for the SIP rams onto the board yet? I realize that actually putting SIPs into the holes would be too expensive, but it would make atari ram expansion < $70/megX16, and MUCH easier. I assume you've calculated the trade-offs between SIP hybrids and "building your own" RAM banks, just out of curiosity, how much of a difference was there (effect on retail price)? The cheapest ram boards I've seen were $100/megabyte, most of the hybrids seem to be priced around $50/megabyte. Right now, the main weakness of the ST is the difficulty of adding RAM. The DMA port could be used for "Paging", but there is no support for such paging.
jsgray@watdragon.UUCP (Jan Gray) (06/28/86)
In article <126@cci632.UUCP> rb@ccird1.UUCP (Rex Ballard) writes: >In article <8606131855.AA04757@ucbvax.Berkeley.EDU> Mike_Wilson@CARLETON.BITNET (Mike Wilson) writes: >>Hi, >> I'm currently working on a project to port a new version of Smalltalk >>(examplar-based, multiple inheritance, multiple PROCESSOR, for those who... What is examplar-based? Good luck! And port it from where? >>... so unless we can >>expand memory to at least 2Meg, we can't use them. "Jan, how come ``Object hash'' never returns a number larger than 255?" "Well, it's a long story...you see, back in 1986 my ST only had 1 Mbyte of RAM..." >According to Abacus literature, the ST series is capable of supporting >4 megabytes, using 1 megabit chips. Caveat here, these must be 1meg by X >not 256x4 or some similar arrangement. There are 20 address lines plus >two RAS and two CAS lines. The MMU doesn't know how to handle 4 banks >of 256x16, but it does appearantly know how to handle 1megx16. A 1 Mbyte DRAM uses 10 address lines, multiplexing the 10 row and 10 column addresses at different times. The multiplexing and other chip timing is controlled by 1 RAS (row address strobe) and 1 CAS (column address strobe) line. A 1 Mbyte DRAM requires 18 pins (cf. 16 pins for 256K DRAMs). The Atari ST MMU has 2 sets of { RAS, CAS-low-byte CAS-high-byte }, so it can directly support 2 banks of RAM, each of which is 16 bits wide. >There is no question that, using 1meg by X chips, you can get at least >2 meg stuffed in there. You could simplify things by getting SIP hybrids. Since 1 Mbyte DRAMs require 18 pins, you will have to bend up between two and four pins on each DRAM and route the wires yourself. Minor PCB surgery (cutting a few traces) will also be required. SIPS would be *more* work! Current 1 Mbyte DRAM price: $75US each from Microprocessors Unlimited. Therefore 2 Mbytes costs $1200, 4 MBytes cost $2400. You'd be wise to wait a few months, it'll probably be $30 each by 4Q86/1Q87. >If you are willing to rebuild the ram banks completely (modest price, some >labor), you can safely get 2 meg for sure. Getting 4 meg depends on >current requirements of the rams, access times, and general loading/timing >requirements of the 1 meg chips. In general, 1 Mbyte DRAMS are faster (100 ns access times), and have roughly the same current requirements of 256K DRAMs. Should be no problem expanding to 4 Mbytes (except for piggy backing hassles). >ATARI: Have you started putting the holes for the SIP rams onto the >board yet? I realize that actually putting SIPs into the holes would >be too expensive, but it would make atari ram expansion < $70/megX16, and >MUCH easier. Atari will make >200000 ST systems this year. They won't add $1 of cost (in terms of PCB space) to each one to make a few hundred hobbyists happy. "You just watch yourself. We're wanted men. I have the death sentence on 12 systems!" Jan Gray jsgray@watdragon University of Waterloo 519-885-1211 x3870